MD, PhD, FMedSci, FRSB, FRCP, FRCPEd.

case-control study

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The use of so-called alternative medicine (SCAM) is common among breast cancer patients, but less is known about whether SCAM influences breast cancer survival. The primary aim of this recent study from Tunesia was to determine the impact of self-use of herbs on the overall survival of women with breast cancer.

The researchers conducted a prospective study including 110 patients with breast cancer. All patients were questioned about their usage of herbal remedies. The demographic data and the overall survival of the patients were then analyzed.

The average age was 51 years (30-80 years old). In total, 37 had metastatic disease (33.6%), and 48 patients had taken plant-based treatments (43.6%). Of those women, 19 patients consumed Graviola (39.6%) and 29 Alenda (60.4%). Overall survival rates at 3 years and at 5 years were 96.2% and 82.4% in the absence of herbal medicine usage versus 78.5% and 78.5% in the presence of herbal medicine use (p = 0.015).

The authors concluded that self-medication with Graviola or Alenda may be associated with an increase of death risk in patients with breast cancer. Further studies are needed to confirm these results.

This is only a small and not very rigorous case-control study. In itself, it would be far from conclusive. What renders it relevant, however, is the fact that its findings do by no means stand alone. We have seen several times on this blog that SCAM use can shorten the life of cancer patients, e.g.:

So, perhaps it is true? Perhaps using SCAM is not such a good idea, if you are suffering from cancer!

The mechanisms of such detrimental effects are not difficult to imagine. They might include direct effects on the cancer, interactions with prescribed drugs, delay of cancer diagnosis, or less strict adherence to the anti-cancer treatments.

 This study aimed to evaluate the effect of Traditional Chinese Medicine (TCM) on patients with gastric cancer following surgery and adjuvant chemotherapy in Taiwan. The cohort sampling data set was obtained from the Registry of Catastrophic Illness Patient Database, a research database of patients with severe illnesses from the National Health Insurance Research Database, Taiwan. Patients who had received a new diagnosis of gastric cancer and had undergone surgery were enrolled. the researchers matched TCM users and nonusers at a ratio of 1 : 3 based on the propensity score, and TCM users were also grouped into short-term and long-term users.

The number of TCM users and nonusers was 1701 and 5103 after applying the propensity score at a ratio of 1 : 3. Short-term users and long-term TCM users were independently associated with a decreased risk of death with HRs of 0.59 (95% confidence interval (CI), 0.55-0.65) and 0.41 (95% CI, 0.36-0.47), respectively, compared with TCM nonusers. The researchers also obtained similar results when they adjusted for covariates in the main model, as well as each of the additional listed covariates. They also observed similar HR trends in short-term users and long-term TCM users among men and women aged <65 years and ≥65 years. The most commonly prescribed single herb and herbal formula in our cohort were Hwang-Chyi (Radix Hedysari; 11.8%) and Xiang-Sha-Liu-Jun-Zi-Tang (15.5%), respectively.

The authors concluded that TCM use was associated with higher survival in patients with gastric cancer after surgery and adjuvant chemotherapy. TCM could be used as a complementary and alternative therapy in patients with gastric cancer after surgery and adjuvant chemotherapy.

This is an interesting study which seems well-done – except for one fatal mistake: even in the title, the authors imply a causal relationship between TCM and survival. Their conclusion has two sentences; the first one speaks correctly of an association. The second, however, not only implies causality but goes much further in suggesting that TCM should be used to prolong the life of patients. Yet, there are, of course, dozens of factors that could interfere with the findings or be the true cause of the observed outcome.

Anyone with a minimum of critical thinking ability should know that CORRELATION IS NOT CAUSATION; sadly, the authors of this study seem to be the exception.

The objective of this survey was to determine

  1. which patients’ characteristics are associated with the use of so-called alternative medicine (SCAM) during cancer treatment,
  2. their pattern of use,
  3. and if it has any association with its safety profile.

A total of 316 patients undergoing chemotherapy treatment in cancer centers in Poland between 2017 and 2019 were asked about their use of SCAM.

Patients’ opinion regarding the safety of unconventional methods is related to the use of SCAM. Moreover, patients’ thinking that SCAM can replace conventional therapy was correlated with his/her education. Moreover, the researchers performed analyses to determine factors associated with SCAM use including sociodemographic and clinical characteristics.

Crucially, they also conducted a survival analysis of patients undergoing chemotherapy with 42 months of follow-up. Using Kaplan-Meier curves and log-rank analysis, they found no statistical difference in overall survival between the groups that used and did not use any form of SCAM.

The authors concluded that SCAM use is common among patients undergoing chemotherapy treatment and should be considered by medical teams as some agents may interact with chemotherapy drugs and affect their efficacy or cause adverse effects.

As I have stated before, I find most surveys of SCAM use meaningless. This article is no exception – except for the survival analysis. It would have merited a separate, more detailed paper, yet the authors hardly comment on it. The analysis shows that SCAM users do not live longer than non-users. Previously, we have discussed several studies that suggested they live less long than non-users.

While this aspect of the new study is interesting, it proves very little. There are, of course, multiple factors involved in the survival of cancer patients, and even if SCAM use were a determinant, it is surely less important than many other factors. To get a better impression of the role SCAM plays, we need studies that carefully match patients according to the most obvious prognostic variables (RCTs would be problematic, difficult to do and unethical). Such studies do exist and they too fail to show that SCAM use prolongs survival, some even suggest it might shorten survival.

I was criticised for not referencing this article in a recent post on adverse effects of spinal manipulation. In fact the commentator wrote: Shame on you Prof. Ernst. You get an “E” for effort and I hope you can do better next time. The paper was published in a third-class journal, but I will nevertheless quote the ‘key messages’ from this paper, because they are in many ways remarkable.

  • Adverse events from manual therapy are few, mild, and transient. Common AEs include local tenderness, tiredness, and headache. Other moderate and severe adverse events (AEs) are rare, while serious AEs are very rare.
  • Serious AEs can include spinal cord injuries with severe neurological consequences and cervical artery dissection (CAD), but the rarity of such events makes the provision of epidemiological evidence challenging.
  • Sports-related practice is often time sensitive; thus, the manual therapist needs to be aware of common and rare AEs specifically associated with spinal manipulative therapy (SMT) to fully evaluate the risk-benefit ratio.

The author of this paper is Aleksander Chaibi, PT, DC, PhD who holds several positions in the Norwegian Chiropractors’ Association, and currently holds a position as an expert advisor in the field of biomedical brain research for the Brain Foundation of the Netherlands. I feel that he might benefit from reading some more critical texts on the subject. In fact, I recommend my own 2020 book. Here are a few passages dealing with the safety of SMT:

Relatively minor AEs after SMT are extremely common. Our own systematic review of 2002 found that they occur in approximately half of all patients receiving SMT. A more recent study of 771 Finish patients having chiropractic SMT showed an even higher rate; AEs were reported in 81% of women and 66% of men, and a total of 178 AEs were rated as moderate to severe. Two further studies reported that such AEs occur in 61% and 30% of patients. Local or radiating pain, headache, and tiredness are the most frequent adverse effects…

A 2017 systematic review identified the characteristics of AEs occurring after cervical spinal manipulation or cervical mobilization. A total of 227 cases were found; 66% of them had been treated by chiropractors. Manipulation was reported in 95% of the cases, and neck pain was the most frequent indication for the treatment. Cervical arterial dissection (CAD) was reported in 57%, and 46% had immediate onset symptoms. The authors of this review concluded that there seems to be under-reporting of cases. Further research should focus on a more uniform and complete registration of AEs using standardized terminology…

In 2005, I published a systematic review of ophthalmic AEs after SMT. At the time, there were 14 published case reports. Clinical symptoms and signs included:

  • central retinal artery occlusion,
  • nystagmus,
  • Wallenberg syndrome,
  • ptosis,
  • loss of vision,
  • ophthalmoplegia,
  • diplopia,
  • Horner’s syndrome…

Vascular accidents are the most frequent serious AEs after chiropractic SMT, but they are certainly not the only complications that have been reported. Other AEs include:

  • atlantoaxial dislocation,
  • cauda equina syndrome,
  • cervical radiculopathy,
  • diaphragmatic paralysis,
  • disrupted fracture healing,
  • dural sleeve injury,
  • haematoma,
  • haematothorax,
  • haemorrhagic cysts,
  • muscle abscess,
  • muscle abscess,
  • myelopathy,
  • neurologic compromise,
  • oesophageal rupture
  • pneumothorax,
  • pseudoaneurysm,
  • soft tissue trauma,
  • spinal cord injury,
  • vertebral disc herniation,
  • vertebral fracture…

In 2010, I reviewed all the reports of deaths after chiropractic treatments published in the medical literature. My article covered 26 fatalities but it is important to stress that many more might have remained unpublished. The cause usually was a vascular accident involving the dissection of a vertebral artery (see above). The review also makes the following important points:

  • … numerous deaths have been associated with chiropractic. Usually high-velocity, short-lever thrusts of the upper spine with rotation are implicated. They are believed to cause vertebral arterial dissection in predisposed individuals which, in turn, can lead to a chain of events including stroke and death. Many chiropractors claim that, because arterial dissection can also occur spontaneously, causality between the chiropractic intervention and arterial dissection is not proven. However, when carefully evaluating the known facts, one does arrive at the conclusion that causality is at least likely. Even if it were merely a remote possibility, the precautionary principle in healthcare would mean that neck manipulations should be considered unsafe until proven otherwise. Moreover, there is no good evidence for assuming that neck manipulation is an effective therapy for any medical condition. Thus, the risk-benefit balance for chiropractic neck manipulation fails to be positive.
  • Reliable estimates of the frequency of vascular accidents are prevented by the fact that underreporting is known to be substantial. In a survey of UK neurologists, for instance, under-reporting of serious complications was 100%. Those cases which are published often turn out to be incomplete. Of 40 case reports of serious adverse effects associated with spinal manipulation, nine failed to provide any information about the clinical outcome. Incomplete reporting of outcomes might therefore further increase the true number of fatalities.
  • This review is focussed on deaths after chiropractic, yet neck manipulations are, of course, used by other healthcare professionals as well. The reason for this focus is simple: chiropractors are more frequently associated with serious manipulation-related adverse effects than osteopaths, physiotherapists, doctors or other professionals. Of the 40 cases of serious adverse effects mentioned above, 28 can be traced back to a chiropractor and none to a osteopath. A review of complications after spinal manipulations by any type of healthcare professional included three deaths related to osteopaths, nine to medical practitioners, none to a physiotherapist, one to a naturopath and 17 to chiropractors. This article also summarised a total of 265 vascular accidents of which 142 were linked to chiropractors. Another review of complications after neck manipulations published by 1997 included 177 vascular accidents, 32 of which were fatal. The vast majority of these cases were associated with chiropractic and none with physiotherapy. The most obvious explanation for the dominance of chiropractic is that chiropractors routinely employ high-velocity, short-lever thrusts on the upper spine with a rotational element, while the other healthcare professionals use them much more sparingly.

Another review summarised published cases of injuries associated with cervical manipulation in China. A total of 156 cases were found. They included the following problems:

  • syncope (45 cases),
  • mild spinal cord injury or compression (34 cases),
  • nerve root injury (24 cases),
  • ineffective treatment/symptom increased (11 cases),
  • cervical spine fracture (11 cases),
  • dislocation or semi-luxation (6 cases),
  • soft tissue injury (3 cases),
  • serious accident (22 cases) including paralysis, deaths and cerebrovascular accidents.

Manipulation including rotation was involved in 42% of all cases. In total, 5 patients died…

To sum up … chiropractic SMT can cause a wide range of very serious complications which occasionally can even be fatal. As there is no AE reporting system of such events, we nobody can be sure how frequently they occur.

[references from my text can be found in the book]

Despite reported widespread use of dietary supplements by cancer patients, few empirical data with regard to their safety or efficacy exist. Because of concerns that antioxidants could reduce the cytotoxicity of chemotherapy, a prospective study was carried out to evaluate associations between supplement use and breast cancer outcomes.

Patients with breast cancer randomly assigned to an intergroup metronomic trial of cyclophosphamide, doxorubicin, and paclitaxel were queried on their use of supplements at registration and during treatment (n =1,134). Cancer recurrence and survival were indexed at 6 months after enrollment.

There were indications that use of any antioxidant supplement (vitamins A, C, and E; carotenoids; coenzyme Q10) both before and during treatment was associated with an increased hazard of recurrence and, to a lesser extent, death. Relationships with individual antioxidants were weaker perhaps because of small numbers. For non-antioxidants, vitamin B12 use both before and during chemotherapy was significantly associated with poorer disease-free survival and overall survival. Use of iron during chemotherapy was significantly associated with recurrence as was use both before and during treatment. Results were similar for overall survival. Multivitamin use was not associated with survival outcomes.

The authors concluded that associations between survival outcomes and use of antioxidant and other dietary supplements both before and during chemotherapy are consistent with recommendations for caution among patients when considering the use of supplements, other than a multivitamin, during chemotherapy.

These data are interesting but, for a range of reasons, not compelling. There might have been several important confounding factors distorting the findings. Even though clinical and life-style variables were statistically adjusted for in this study, it might still be possible that supplement users and non-users were not comparable in impotant prognostic variables. Simply put, sicker patients might be more likely to use supplements and would then have worse outcomes not because of the supplements but their disease severity.

Moreover, it seems important to note that other research showed the opposite effects. For instance, a study prospectively examined the associations between antioxidant use after breast cancer (BC) diagnosis and BC outcomes in 2264 women. The cohort included women who were diagnosed with early stage, primary BC from 1997 to 2000 who enrolled, on average, 2 years postdiagnosis. Baseline data were collected on antioxidant supplement use since diagnosis and other factors. BC recurrence and mortality were ascertained, and hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated.

Antioxidant supplement use after diagnosis was reported by 81% of women. Among antioxidant users, frequent use of vitamin C and vitamin E was associated with a decreased risk of BC recurrence. Vitamin E use was associated with a decreased risk of all-cause mortality. Conversely, frequent use of combination carotenoids was associated with increased risk of death from BC and all-cause mortality.

The authors concluded that frequent use of vitamin C and vitamin E in the period after BC diagnosis was associated with a decreased likelihood of recurrence, whereas frequent use of combination carotenoids was associated with increased mortality. The effects of antioxidant supplement use after diagnosis likely differ by type of antioxidant.

Yet another study provided limited support for the hypothesis that antioxidant supplements may reduce the risk of breast cancer recurrence or breast cancer-related mortality.

Confused?

Me too!

What is needed, it seems, is a systematic review of all these contradicting studies. A 2009 review is available of the associations between antioxidant supplement use during breast cancer treatment and patient outcomes.

Inclusion criteria were: two or more subjects; clinical trial or observational study design; use of antioxidant supplements (vitamin C, vitamin E, antioxidant combinations, multivitamins, glutamine, glutathione, melatonin, or soy isoflavones) during chemotherapy, radiation therapy, and/or hormonal therapy for breast cancer as exposures; treatment toxicities, tumor response, recurrence, or survival as outcomes.

A total of 22 articles met the criteria. Their findings did not support any conclusions regarding the effects of individual antioxidant supplements during conventional breast cancer treatment on toxicities, tumor response, recurrence, or survival. A few studies suggested that antioxidant supplements might decrease side effects associated with treatment, including vitamin E for hot flashes due to hormonal therapy and glutamine for oral mucositis during chemotherapy. Underpowered trials suggest that melatonin may enhance tumor response during treatment.

The authors concluded that the evidence is currently insufficient to inform clinician and patient guidelines on the use of antioxidant supplements during breast cancer treatment. Thus, well designed clinical trials and observational studies are needed to determine the short- and long-term effects of such agents.

Still confused?

Me too!

Antioxidants seem to have evolved as parts of elaborate networks in which each substance plays slightly different roles. This means that each antioxidant has a different spectrum of actions. And this means that it is probably not very constructive to lump them all together and excect to see uniform effects. What we would need to create more clarity is a series of RCTs on single antioxidants. But who is going to fund them? We might be waiting a long time for more clarity. Meanwhile, consuming a healthy and well-balanced diet might be the best advice for cancer patients and everyone else.

This study assessed the patterns of dietary supplement usage among cancer survivors in the United States in a population-based setting. National Health and Nutrition Examination Survey (NHANES) datasets (1999-2016) were accessed, and adult respondents (≥ 20 years old) with a known status of cancer diagnosis and a known status of dietary supplements intake were included. Multivariable logistic regression analysis was then used to assess factors associated with dietary supplements intake. Moreover, and to evaluate the impact of dietary supplements on overall survival among respondents with cancer, multivariable Cox regression analysis was conducted.

A total of 49,387 respondents were included in the current analysis, including a total of 4,575 respondents with cancer. Among respondents with cancer, 3,024 (66.1%) respondents reported the use of dietary supplements; while 1,551 (33.9%) did not report the use of dietary supplements. Using multivariable logistic regression analysis, factors associated with the use of dietary supplements included:

  • older age (OR: 1.028; 95% CI: 1.027-1.030);
  • white race (OR for black race vs. white race: 0.67; 95% CI: 0.63-0.72);
  • female gender (OR for males vs. females: 0.56; 95% CI: 0.53-0.59),
  • higher income (OR: 1.13; 95% CI: 1.11-1.14),
  • higher educational level (0.59; 95% CI: 0.56-0.63),
  • better self-reported health (OR: 1.36; 95% CI: 1.17-1.58),
  • health insurance (OR: 1.35; 95% CI: 1.27-1.44),
  • history of cancer (OR: 1.20; 95% CI: 1.10-1.31).

Using multivariable Cox regression analysis and within the subgroup of respondents with a history of cancer, the use of dietary supplements was not found to be associated with a difference in overall survival (HR: 1.13; 95% CI: 0.98-1.30).

The authors concluded that dietary supplement use has increased in the past two decades among individuals with cancer in the United States, and this increase seems to be driven mainly by an increase in the use of vitamins. The use of dietary supplements was not associated with any improvement in overall survival for respondents with cancer in the current study cohort.

Many cancer patients, when they first get diagnosed, are tested for vitamin D levels and found to be low or borderline. Consequently, they get a prescription for supplements. Other than this, there is rarely an indication to take any vitamins or other dietary supplements. Yet, cancer patients take them because they think these ‘natural’ preparations can do no harm (and because the industry can be persuasive [there is big money at stake] and the odd breed of ‘integrated’ oncologists might even recommend them). Sadly, this assumption is not correct. The biggest danger, in my view, is the possibility of supplements to interact with one of the many drugs that cancer patients need to take. So, in a way, it is reassuring that, on average, there is no detrimental effect on overall survival.

The paper will probably also reignite the perennial discussion about the effects of vitamin C on the natural history of cancer. My understanding is that there is none (and this verdict seems to be supported by the findings reported here). But I am, of course, aware that this is a ‘hot potato’ and that some readers will think differently. To them I say: please show me the evidence.

A 2020 article that I just came across concluded with this rather remarkable statement:

High-dose enzyme therapy is a natural cancer protocol that has been highly successful in treating this much-feared disease.

Since we can find a plethora of similar claims on social media and elsewhere, it is high time, I think, to dedicate a post to this alleged cancer cure.

Enzyme therapy involves the administration of proteolytic enzymes by mouth. Proteolytic enzymes are large molecules that are nevertheless said to be absorbed in the gut before they are dispersed into different compartments of the body where they can be detected in various concentrations. Proteolytic enzymes (serine endopeptidases such as trypsin or chymotrypsin and cysteine endo-proteinases such as bromelain and papain or combinations of those enzymes) have long been available for diverse medical indications, including cancer. They are claimed to exert anticancer activities by restoring the reduced cytotoxic activity of patients’ sera.

Enzyme therapy has been subjected to experimental investigations and to a few studies in cancer patients. A systematic review claimed that, for plasmacytoma patients, systemic enzyme therapy was shown to increase the response rates, the duration of remissions, and the overall survival times.[1]

This statement is based on just one study. Here is its abstract[2]:

Purpose: To evaluate the impact of an additive therapy with an oral enzyme (OE) preparation given for more than 6 months additionally to standard combination chemotherapy (vincristine/melphalan/cyclophosphamide/prednisone (VMCP)- or methylprednisolone/ vincristine/CCNU/cyclophosphamide/melphalan (MOCCA)-regimen) in the primary treatment of patients with multiple myeloma stages I-III.

Methods: A cohort of 265 patients with multiple myeloma stages I-III was consecutively treated at our institution in two parallel groups (control group (n = 99): chemotherapy +/-OE for less than 6 months; OE-group (n = 166): chemotherapy + OE for more than 6 months). The median follow-up time in the stages I, II, and III for the OE-group was 61, 37, and 46.5 months, respectively; for the control group the respective values were 33, 51.5, and 31.5 months. The primary endpoint of the study was disease-specific survival. Secondary endpoints were response to therapy, duration of first response and side effects. The chosen method for evaluation was the technique of a retrolective cohort analysis with a concurrent control group. Survival analysis was performed by the Kaplan-Meier method and multivariate analysis was done with the Cox proportional hazards model.

Results: Significantly higher overall response rates and longer duration of remissions were observed in the OE-group. Primary responders showed a longer mean survival time than non-responders. Additive therapy with OE given for more than 6 months decreased the hazard of death for patients at all stages of disease by approximately 60%. Observation time was not long enough to estimate the median survival for patients at stages I and II; for stage III patients it was 47 months in the control group versus 83 months for the patients treated with OE (P = 0.0014) which means a 3-year gain of survival time. Significant prognostic factors for survival, in the Cox regression analysis, were stage of disease and therapy with OE. The OE-therapy was generally well tolerated (3.6% of patients with mild to moderate gastrointestinal symptoms).

Conclusion: OEs represent a promising new additive therapy in multiple myeloma which will be further evaluated in a randomized phase III trial in the USA.

My searches located no prospective clinical trials supporting the notion that enzyme therapy is an effective cancer cure for any type of human cancer. So, what about the bold statement quoted above? In my view, it is a dangerous and highly irresponsible claim that endangers the lives of many vulnerable cancer patients desperately looking for alternative cancer cures.

REFERENCES

[1] Beuth J. Proteolytic enzyme therapy in evidence-based complementary oncology: fact or fiction? Integr Cancer Ther. 2008 Dec;7(4):311-6. doi: 10.1177/1534735408327251. PMID: 19116226.

[2] Sakalová A, Bock PR, Dedík L, Hanisch J, Schiess W, Gazová S, Chabronová I, Holomanova D, Mistrík M, Hrubisko M. Retrolective cohort study of an additive therapy with an oral enzyme preparation in patients with multiple myeloma. Cancer Chemother Pharmacol. 2001 Jul;47 Suppl:S38-44. doi: 10.1007/s002800170008. PMID: 11561871.

This analysis was aimed at assessing the associations of acupuncture use with mortality, readmission and reoperation rates in hip fracture patients using a longitudinal population-based database. A retrospective matched cohort study was conducted using data for the years 1996-2012 from Taiwan’s National Health Insurance Research Database. Hip fracture patients were divided into:

  • an acupuncture group consisting of 292 subjects who received at least 6 acupuncture treatments within 183 days of hip fracture,
  • and a propensity score matched “no acupuncture” group of 876 subjects who did not receive any acupuncture treatment and who functioned as controls.

The two groups were compared using survival analysis and competing risk analysis.

Compared to non-treated subjects, subjects treated with acupuncture had

  • a lower risk of overall death (hazard ratio (HR): 0.41, 95% confidence interval (CI): 0.24-0.73, p = 0.002),
  • a lower risk of readmission due to medical complications (subdistribution HR (sHR): 0.64, 95% CI: 0.44-0.93, p = 0.019)
  • and a lower risk of reoperation due to surgical complications (sHR: 0.62, 95% CI: 0.40-0.96, p = 0.034).

The authors concluded that postoperative acupuncture in hip fracture patients is associated with significantly lower mortality, readmission and reoperation rates compared with those of matched controls.

That’s a clear and neat finding; the question is, what does it mean?

Here are a few possibilities for consideration:

  1. As a result of having at least 6 acupuncture sessions, patients had lower rates of mortality, readmission and reoperation.
  2. As a result of having lower rates of mortality, readmission and reoperation, patients used acupuncture.
  3. As a result of some other factor, patients had both lower rates of mortality, readmission and reoperation and at least 6 sessions of acupuncture.

Which of the three possibilities is the most likely?

  1. Some enthusiasts might think that acupuncture makes you live longer. But does anyone truly believe it reduces the likelihood of needing a reoperation? Seriously? Well, I don’t see even a hint of a mechanism by which acupuncture might achieve this. Therefore, I would categorise this possibility as highly unlikely.
  2. It stands to reason that patients who are alive and well use more acupuncture than those who are dead or in need of surgery. So, this possibility is not entirely inconceivable.
  3. It seems very likely that people who are more health conscious might use acupuncture and live longer, need less readmissions or surgery. No doubt, this possibility is by far the best explanation of the findings of this retrospective matched cohort study.

If that is so, does this paper tell us anything useful at all?

Not really (that’s why it was published in an acupuncture journal which few people would read)

On second thought, perhaps it does tell us something valuable: retrospective matched cohort studies are hopeless when it comes to establishing cause and effect!

Glucosamine is currently one of the most popular of all dietary supplements. It is marketed as a treatment for arthritis, and there is some evidence that it is moderately helpful for this indication. But evidence had been accumulating to suggest that glucosamine might have other effects as well. The latest analysis evaluated the associations of regular glucosamine use with all-cause and cause-specific mortality in a large prospective cohort.

This population-based prospective cohort study included 495 077 women and men from the UK Biobank study. Participants were recruited from 2006 to 2010 and were followed up through 2018. The investigators evaluated all-cause mortality and mortality due to cardiovascular disease (CVD), cancer, respiratory and digestive disease. Hazard ratios (HRs) and 95% CIs for all-cause and cause-specific mortality were calculated using Cox proportional hazards models with adjustment for potential confounding variables.

At baseline, 19.1% of the participants reported regular use of glucosamine supplements. During a median follow-up of 8.9 years (IQR 8.3-9.7 years), 19 882 all-cause deaths were recorded, including 3802 CVD deaths, 8090 cancer deaths, 3380 respiratory disease deaths and 1061 digestive disease deaths. In multivariable adjusted analyses, the HRs associated with glucosamine use were 0.85 (95% CI 0.82 to 0.89) for all-cause mortality, 0.82 (95% CI 0.74 to 0.90) for CVD mortality, 0.94 (95% CI 0.88 to 0.99) for cancer mortality, 0.73 (95% CI 0.66 to 0.81) for respiratory mortality and 0.74 (95% CI 0.62 to 0.90) for digestive mortality. The inverse associations of glucosamine use with all-cause mortality seemed to be somewhat stronger among current than non-current smokers (p for interaction=0.00080).

The authors concluded that regular glucosamine supplementation was associated with lower mortality due to all causes, cancer, CVD, respiratory and digestive diseases.

Previous epidemiological investigations indicated that glucosamine use might play a role in prevention of cancer, cardiovascular disease and other diseases. This suggests that the finding is more than the result of a large ‘fishing expedition’ to which epidemiological studies are sadly prone. It we are indeed dealing with a true phenomenon, we should ask by what mechanism these remarkable outcomes might be achieved. It is well documented that glucosamine has powerful anti-inflammatory effects. Therefore it is conceivable that such anti-inflammatory mechanisms are the cause for the observed outcomes.

How do we prove or disprove the hypothesis that glucosamine reduces the mortality of a range of diseases? A reasonable starting point would be to consult the good old Hill criteria of causality:

(1) The strength of association is small to moderate – certainly not strong

(2) The consistency of the findings is quite remarkable; that is unless dozens of epidemiological studies that failed to yield and association were never published.

(3) The specificity of the association with diseases linked to inflammation is also impressive (with the caveat above).

(4) Temporality seems also not a problem, as far as I can see.

(5) Biological gradient needs further testing, I think.

(6) Plausibility is not a problem, since there is a possible mechanism that could explain the findings.

(7) The same applies to coherence.

(8) Experiment is needed, but it is far from easy to conduct clinical trials where mortality is an endpoint.

(9) Analogy is realised through the well-established concept of (cardiovascular) risk factors.

What does all this actually mean?

It means, I think, that glucosamine could well have clinical effects that go far beyond easing the pain of arthritis. However, we cannot be sure. Once again, it boils down to the need of robust clinical trial data. The subject certainly seems important enough to consider this option.

 

When tested rigorously, the evidence for so-called alternatives medicine (SCAM) is usually weak or even negative. This fact has prompted many SCAM enthusiasts to become utterly disenchanted with rigorous tests such as the randomised clinical trial (RCT). They seem to think that, if the RCT fails to generate the findings we want, let’s use different methodologies instead. In other words, they are in favour of observational studies which often yield positive results.

This line of thinking is prevalent in all forms of SCAM, but probably nowhere more so that in the realm of homeopathy. Homeopaths see that rigorous RCTs tend not to confirm their belief and, to avoid cognitive dissonance, they focus on observational studies which are much more likely to confirm their belief.

In this context, it is worth mentioning a recent article where well-known homeopathy enthusiasts have addressed the issue of observational studies. Here is their abstract:

Background: Randomized placebo-controlled trials are considered to be the gold standard in clinical research and have the highest importance in the hierarchical system of evidence-based medicine. However, from the viewpoint of decision makers, due to lower external validity, practical results of efficacy research are often not in line with the huge investments made over decades.

Method: We conducted a narrative review. With a special focus on homeopathy, we give an overview on cohort, comparative cohort, case-control and cross-sectional study designs and explain guidelines and tools that help to improve the quality of observational studies, such as the STROBE Statement, RECORD, GRACE and ENCePP Guide.

Results: Within the conventional medical research field, two types of arguments have been employed in favor of observational studies. First, observational studies allow for a more generalizable and robust estimation of effects in clinical practice, and if cohorts are large enough, there is no over-estimation of effect sizes, as is often feared. We argue that observational research is needed to balance the current over-emphasis on internal validity at the expense of external validity. Thus, observational research can be considered an important research tool to describe “real-world” care settings and can assist with the design and inform the results of randomised controlled trails.

Conclusions: We present recommendations for designing, conducting and reporting observational studies in homeopathy and provide recommendations to complement the STROBE Statement for homeopathic observational studies.

In their paper, the authors state this:

It is important to realize three areas where observational research can be valuable. For one, as already mentioned, it can be valuable as a preparatory type of research for designing good randomized studies. Second, it can be valuable as a stand-alone type of research, where pragmatic or ethical reasons stand against conducting a randomized study. Additionally, it can be valuable as the only adequate method where choices are involved: for instance, in any type of lifestyle research or where patients have very strong preferences, such as in homeopathy and other CAM. This might also lead to a diversification of research efforts and a broader, more realistic, picture of the effects of therapeutic interventions.

My comments to this are as follows:

  1. Observational research can be valuable as a preparatory type of research for designing good randomized studies. This purpose is better fulfilled by pilot studies (which are often abused in SCAM).
  2. Observational research can be valuable as a stand-alone type of research, where pragmatic or ethical reasons stand against conducting a randomized study. Such situations rarely arise in the realm of SCAM.
  3. Observational research can be valuable as the only adequate method where choices are involved: for instance, in any type of lifestyle research or where patients have very strong preferences, such as in homeopathy and other CAM. I fail to see that this is true.
  4. Observational research leads to a diversification of research efforts and a broader, more realistic, picture of the effects of therapeutic interventions. The main aim of research into the effectiveness of SCAM should be, in my view, to determine whether the treatment per se works or not. Observational studies are likely to obscure the truth on this issue.

Don’t get me wrong, I am not saying that observational studies are useless; quite to the contrary, they can provide very important information. But what I am trying to express is this:

  • We should not allow double standards in medical research. The standards and issues of observational research as they exist in conventional medicine must also apply to SCAM.
  • Observational studies cannot easily determine cause and effect between the therapy and the outcome.
  • Observational studies cannot be a substitute for RCTs.
  • Depending on their exact design, observational studies measure the outcome caused by a whole range of factors, including the therapy per se, the placebo-effect, the natural history of the disease, the regression towards the mean.
  • Observational studies are particularly useful in effectiveness research, AFTER the efficacy of a therapy has been established by RCTs.
  • If RCT fail to show that a therapy is effective and observational studies seem to indicate that they work, the therapy in question is probably a placebo.
  • SCAM-enthusiasts’ preference for observational studies is transparently due to motivated reasoning.
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