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

EBM

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In response to criticism voiced against Australian chiropractors’ decision to re-commence manipulating children, the Australian Chiropractors Association (ACA) president, David Cahill, welcomed the updated statement on paediatric care by the Chiropractic Board of Australia. “The statement serves to reinforce the confidence the Australian public has in chiropractic care provided by registered ACA member chiropractors,” said Cahill.

The Safer Care Victoria Review has shown chiropractic care for children to be extremely safe. Of the 29,599 online submissions received from across Australia (the largest survey of its kind), there were no reports of harm to a child receiving chiropractic healthcare. Of those submissions, 21,824 responses were from parents who had accessed chiropractic healthcare for their children, and there was not a single report of significant harm in these submissions. “In a particularly strong endorsement, 99.6% of those parental submissions affirmed that chiropractic healthcare benefitted their child highlighting the exemplary safety record of chiropractic healthcare,” Cahill said.

ACA member chiropractors are healthcare professionals who effectively treat a wide range of musculoskeletal disorders. Chiropractors are 5-year university degree educated healthcare professionals, equipped with expertise enabling them to tailor the appropriate care for people of all ages including children. Established in 1938, the Australian Chiropractors Association (ACA) is the peak body representing chiropractors. The ACA promotes the importance of maintaining spinal health to improve musculoskeletal health through non-invasive, drug-free spinal health and lifestyle advice to help Australians of all ages lead and maintain healthy lives.

_________________________

Mr Cahill and the Australian Chiropractors Association have thus demonstrated that they fail to understand how one needs to establish the benefits and harms of a therapy. That chiropractic spinal manipulations are “extremely safe” cannot be established by an online survey which might or might not have been manipulated by the chiropractors who have an interest in not loosing the lucrative option of treating children. It cannot even establish “the confidence the Australian public has in chiropractic care”.

Mr Cahill and the Australian Chiropractors Association should know that chiropractic spinal manipulation – just like any other intervention – must be evaluated according to accepted principles of risk-benefit analyses. No proven benefit and a possibility of harm mean that the risk-benefit balance fails to be positive. And this means that it is irresponsible to use chiropractic spinal manipulations.

Mr Cahill and the Australian Chiropractors Association, however, seem to not know even the essentials of ethical healthcare. The obvious conclusion, therefore, is to send the lot of them back to school.

On 8 March 2019, the Council of Australian Governments (COAG) Health Council (CHC) noted community concerns about spinal manipulation on children performed by chiropractors and agreed that there was a need to consider whether public safety was at risk.

On behalf of the CHC, the Victorian Minister for Health, the Hon. Jenny Mikakos MP, instructed Safer Care Victoria (SCV) to undertake an independent review of the practice of chiropractic spinal manipulation on children under 12 years. The findings of this review are to be provided to the Minister for reporting to the CHC. To provide expert guidance and advice to inform the review, SCV established an independent advisory panel. The panel included expertise in chiropractic care, academic allied health, health practitioner regulation, healthcare evidence, governance, paediatrics and paediatric surgery, and musculoskeletal care, and had consumer representation.

The main conclusions were as follows:

  • … spinal manipulation in children is not wholly without risk. Any risk associated
    with care, no matter how uncommon or minor, must be considered in light of any potential or likely
    benefits. This is particularly important in younger children, especially those under the age of 2 years in
    whom minor adverse events may be more common.
  • … the evidence base for spinal manipulation in children is very poor. In particular, no studies have been performed in Australia … The possible, but unlikely, benefits of spinal manipulation in the management of colic or enuresis should be balanced by the possibility, albeit rare, of minor harm.

The main recommendation was straight forward: “Spinal manipulation, as defined in Section 123 of National Law, should not be provided to children under 12 years of age, by any practitioner, for general wellness or for the management of the following conditions: developmental and behavioural disorders, hyperactivity disorders, autism spectrum disorders, asthma, infantile colic, bedwetting, ear infections, digestive problems, headache, cerebral palsy and torticollis.”

The Chiropractic Board of Australia nevertheless decided they would re-start manipulationg babies. On 11/6/2024 The Sydney Morning Harald reported:

Chiropractors have given themselves the green light to resume manipulating the spines of babies following a four-year interim ban supported by the country’s health ministers. In a move slammed by doctors as irresponsible, the Chiropractic Board of Australia has quietly released new guidelines permitting the controversial treatment for children under two. The Royal Australian College of General Practitioners (RACGP) hit out at the decision, saying there was no evidence supporting the spinal manipulation of babies and children and that the practice should be outlawed. ‘‘There is no way in the world I would let anyone manipulate a child’s spine,’’ said Dr James Best, the college’s Specific Interests Child and Young Person’s Health chair. ‘‘The fact that it hasn’t been ruled out by this organisation is very disappointing and concerning. It’s irresponsible.’’ …

Subsequently, it was reported that the federal health minister has intervened in the Chiropractic Board of Australia’s controversial decision to allow practitioners to resume spinal manipulation of children under two and is seeking an urgent explanation.

As pressure mounts on chiropractors to ditch the treatment, federal Health Minister Mark Butler confirmed on Thursday that he would also raise the issue with his state and territory colleagues at a meeting of health ministers in South Australia on Friday.

“The Health Minister is writing to the Chiropractic Board seeking an urgent explanation on its decision to allow a resumption of spinal manipulation of infants under two, in spite of two reviews concluding there was no evidence to support that practice,” a spokeswoman said.

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This course of events can only be surprising to those who are not familiar with the chiropractors’ general attitude. Chiropractors have always put income before ethics and safety. This, I fear, is not a phenomenon confined to Australia or to the care of children but one that beleagues this profession worldwide from the days of DD Palmer to the present.

The over-use of X-ray diagnostics by chiropractors has been the topic of previous posts, e.g.:

The authors of this review state that many clinicians use radiological imaging in efforts to locate and diagnose the cause of their patient’s pain, relying on X-rays as a leading tool in clinical evaluation. This is fundamentally flawed because an X-ray represents a “snapshot” of the structural appearance of the spine and gives no indication of the current function of the spine. The health and well-being of any system, including the spinal motion segments, depend on the inter-relationship between structure and function. Pain, tissue damage, and injury are not always directly correlated. Due to such a high incidence of abnormalities found in asymptomatic patients, the diagnostic validity of X-rays can be questioned, especially when used in isolation of history and/or proper clinical assessment. The utility of routine X-rays is, therefore, questionable. One may posit that their application promotes overdiagnosis, and unvalidated treatment of X-ray findings (such as changes in postural curvature), which may mislead patients into believing these changes are directly responsible for their pain. A substantial amount of research has shown that there is no association between pain and reversed cervical curves. Accuracy can also be questioned, as X-ray measurements can vary based on the patient’s standing position, which research shows is influenced by an overwhelming number of factors, such as patient positioning, patient physical and morphological changes over time, doctor interreliability, stress, pain, the patient’s previous night’s sleep or physical activity, hydration, and/or emotional state. Furthermore, research has concluded that strong evidence links various potential harms with routine, repeated X-rays, such as altered treatment procedures, overdiagnosis, radiation exposure, and unnecessary costs. Over the past two decades, medical boards and health associations worldwide have made a substantial effort to communicate better “when” imaging is required, with most education around reducing radiographic imaging. In this review, we describe concerns relating to the high-frequency, routine use of spinal X-rays in the primary care setting for spine-related pain in the absence of red-flag clinical signs.

Many chiropractors over-use X-rays (not least because it is a significant source of income) and claim to be able diagnose subluxations with X-ray diagnostics. The authors of the review state are unimpressed by this habit:

Spinal X-rays can lead to the detection of radiographic findings that can be used as an overdiagnosis for the patient, even though they may be asymptomatic. These include spinal anomalies, osteophytes, reduced disc heights, low-grade spondylolisthesis, transitional segments, and spina bifida occulta. The chiropractor can use all radiographic findings as “scare tactics” or “fear-mongering” to retain a patient under a specific frequency of care, thus creating unnecessary concern for the patient. Multiple studies have concluded that radiographic findings do not always correlate with a patient’s symptomatology. Brinjikji et al. (2015) concluded that disc degeneration was present in asymptomatic individuals, ranging from 37% in 20 year olds to 96% in 80 year olds.

Many chiropractors use “phases of degeneration” as a method of communication in order for patients to adhere to excessive treatment plans. It is unnecessary and unethical to scare patients to obtain compliance with chiropractic care. These “scare tactics” can negatively influence patients’ behavior, especially those who already experience reduced levels of self-efficacy. This unnecessary use of communication can cause negative thoughts, leading to fear of avoidance of physical activity and management advice as there is a concern for further damage. In addition, the likelihood that a patient will experience chronic pain may arise due to the belief that they won’t get better until the radiographic findings are resolved.

Vertebral subluxation is a term and condition created by chiropractors that refers to misalignment of the vertebra, a bone out of place, causing pressure on the spinal nerve and interference with mental impulses. Subluxation is a legitimate medical condition; however, this completely differs from the condition used by chiropractors. Over the years, there have been numerous definitions and takes on what “vertebral subluxation” is – even though the term and concept date back to 1902, it is still commonly used in the chiropractic community. It has been described that the misalignment of the vertebra causes occlusion of where the spinal nerve travels, thus causing nerve pressure and disrupting the “mental impulse,” which is part “intelligence,” a synonym for “spirit” and part of the “mental realm,” and part neural impulse; which is part of the physical realm. Many chiropractors believe that when bones press on nerves, the corresponding organ on the other end of the nerve will suffer disease. At this point, it appears more like religion; however, it is crucial that we include this as many clinicians use this “condition” as grounds to order unnecessary radiographic imaging. Extensive medical research has shown that bones do not slip out of place, squishing nerves causing various and different pathologies – and there is certainly no way to scientifically prove the interference of a “spirit” or life force. Nonetheless, none of this is grounds for ordering an X-ray and does not qualify as any type of “red flag,” raising concern about how and when chiropractors are using radiographic imaging.

The authors conclude that the importance of medical imaging cannot be overstated. Medical professionals, on the other hand, must adhere to ethical and responsible standards. These guidelines may be ambiguous in some situations, professions, and countries, resulting in many gray areas of practice. As discussed in this review, the ongoing justification many use to justify the excessive, repetitive, and ongoing use of X-rays for reasons that research does not support is highly concerning. This article highlights potential unvalidated practices within the chiropractic field relating to poor utility imaging.

 

This systematic review and meta-analysis investigated the impact of quality of life (QoL) on mortality risk in patients with esophageal cancer.

A literature search was conducted using the CINAHL, PubMed/MEDLINE, and Scopus databases for articles published from inception to December 2022. Observational studies that examined the association between QoL and mortality risk in patients with esophageal cancer were included. Subgroup analyses were performed for time points of QoL assessment and for types of treatment.

Seven studies were included in the final analysis.

  • Overall, global QoL was significantly associated with mortality risk (hazard ratio 1.02, 95% confidence interval 1.01–1.04; p < 0.00004).
  • Among the QoL subscales of QoL, physical, emotional, role, cognitive, and social QoL were significantly associated with mortality risk.
  • A subgroup analysis by timepoints of QoL assessment demonstrated that pre- and posttreatment global and physical, pretreatment role, and posttreatment cognitive QoL were significantly associated with mortality risk.
  • Moreover, another subgroup analysis by types of treatment demonstrated that the role QoL in patients with surgery, and the global, physical, role, and social QoL in those with other treatments were significantly associated with mortality risk.

The authors concluded that these findings indicate that the assessment of QoL in patients with esophageal cancer before and after treatment not only provides information on patients’ condition at the time of treatment but may also serve as an outcome for predicting life expectancy. Therefore, it is important to conduct regular QoL assessments and take a proactive approach to improve QoL based on the results of these assessments.

Am I missing something here?

Isn’t this rather obvious?

The way this paper is written, some practitioners of so-called alternative medicine (SCAM) might feel that, by improving QoL (for instance, by some fancy aromatherapy, reflexology, etc.), they can significantly better the cancer prognosis.

Patients with a poor prognosis are more seriously ill and therefore have a lowe QoL. Assessing QoL might be a useful marker, but would it not be better to ask why the QoL is in some patients less than in others?

For some time I have had the impression that research into SCAM is on its knees. Specifically, I seemed to notice that less and less of it is getting published in the best journals of conventional medicine. So, today I decided to put my impression to the test.

I went on Medline and serached for ‘COMPLEMENTARY ALTERNATIVE THERAPY + NEJM or Ann Int Med or Lancet or JAMA. This gave me the number of papers each of these four top medical journals published during the last decades. These figures alone seemed to indicate that I was on to something. To get a more reliable overall pivture, I added them up to get the total number of SCAM articles per year published in all four jurnals. As these figures indicated a lot of noise, I grouped them into periods of 4 years.

Here are the results:

  • Number of papers in the four journals published between 1999 and 2002 =115
  • Number of papers in the four journals published between 2003 and 2006 = 44
  • Number of papers in the four journals published between 2007 and 2010 = 20
  • Number of papers in the four journals published between 2011 and 2014 = 23
  • Number of papers in the four journals published between 2015 and 2018 = 38
  • Number of papers in the four journals published between 2019 and 2022 = 36

These figures confirm my suspicion: top medical journals publish far less SCAM articles than they once used to. But how do we interpret this finding?

The way I see it, there are several possible explanations:

  1. The editors are becoming increasingly anti-SCAM.
  2. Less and less SCAM research is of high enough quality to merit publication in a top journal.
  3. Numerous SCAM journals have sprung up which absorb most of the SCAM research but which are largely ignored by the broader medical community.

Personally, I think all of these explanations apply. They are the expression of a phenomenon that I discussed often before: over the years, SCAM has managed to discredit and isolate itself. Thus, it is no longer taken seriously and in danger of becoming a bizarre cult.

I fear that serious healthcare professionals get increasingly irritated by:

  • the embarrassing unreliability of much of SCAM research (as discussed so many times on this blog);
  • the fact that some research group manage to publish nothing but positive results (see my ‘ALTERNATIVE MEDICINE HALL OF FAME);
  • the news that a substantial proportion of SCAM research seems fabricated (see, for instance, here);
  • the fact that too much of SCAM research is of dismal quality (as disclosed regularly on this blog);
  • the fact that many SCAM proponents are unable of (self)critical thinking (as demonstrated regualrly by the comments left on this blog).

If I am correct, this would mean that, in the long-term, one of the biggest enemy of SCAM are the SCAM researchers who, instead of testing hypotheses, abuse science by trying to confirm their hypotheses. As Bert Brecht said: the opposite of good is not evil, but good intentions.

Although the vaccine has many individual and social benefits, ‘Vaccine Hesitancy’ has led to an increase in the number of vaccine-preventable diseases.

The aim of this study is to determine the effect of ideas that cause vaccine hesitancy to comply with traditional medicine practices and drugs and to determine the ratio of parents’ preference for so-called alternative medicine (SCAM).

This study was performed on the parents who refused vaccination in their children under the age of 8 between the years 2017-2022. Parents of the vaccinated children who were matched for age and gender were determined as the control group. Demographic characteristics of families, education levels, compliance ratios for well-child follow-up and pregnancy follow-up, preference ratios for traditional medicine and/or SCAM applications were compared.

A total of 123 families, 61 of whom were vaccine refusal and 62 of the control group, were included in the study. It was determined that the ratio of parents who refuse vaccination have increased in the last five years. The education level was found to be higher in the SCAM group (p=0.019). The most common reasons for vaccine refusal were distrust of the vaccine content (72.1%) and noncompliance with religious beliefs (49.1%). It was also found that the ratios of prophylactic vitamin use and tetanus vaccination of mothers during pregnancy were lower in the SCAM group. While the rate of compliance with vitamin D and iron prophylaxis for infants was lower in the vaccine refusal group, the ratio of preference for SCAM was higher.

The authors conclused that vaccine hesitancy is a complex issue that affects public health, in which many individual, religious, political and sociological factors play a role. As with recent studies, this research shows that the most important reason for vaccine rejection is “lack of trust”. The higher education level in the vaccine refusal group may also be a sign of this distrust. Not only the rejection of the vaccine, but also the lack of use of vitamin drugs seems to be related to lack of trust. This may also cause SCAM methods to be preferred more. These results show that providing trust in vaccination is the biggest step in the fight against vaccine hesitancy.

We have discussed the link between SCAM and vaccination hesitancy many times before, e.g.:

This new study seems to imply that the common denominator of both SCAM use and vaccination hesitancy is distrust, distrust in vaccinations and distrust in conventional medicine. That makes sense at first glance but not when you think about it for only a minute.

I can see why people distrust conventional medicine (to some extend, I do it myself). But why should distrust motivate some people to put their trust into SCAM which is even less trustworthy than conventional medicine. The rational thing for a distrusting person would be to critically assess the evidence and go where the evidence leads him/her. This path cannot possibly lead to SCAM but would lead to the best available evidence-based therapies.

If we consider this carefully, we arrive at the conclusion that not distrust but a degree of irrationality is more likely be the common denominator between SCAM use and vaccination hesitancy.

What do you think?

Yes, I have done it again: another book!

Bizarre Medical Ideas: … and the Strange Men Who Invented Them

In order to let you know what it is all about, allow me to post the intoduction here:

Medicine has always relied on extraordinary innovators. Without them, progress would hardly have been possible, and we might still believe in the four humours and be treated with blood letting, mercury potions, or purging. The history of medicine is therefore to a large extent the history of its pioneers. This book is about some of them. It focusses on the mavericks who separated themselves from the mainstream and invented alternative medicine, healthcare that remained outside conventional medicine.

Few people would deny that differences of opinion are necessary for progress. This is true for healthcare as it is for any other field. Divergent views and legitimate debate have always been important drivers of innovation. Yet, some opinions have been so thoroughly repudiated by evidence as to be considered demonstrably wrong and harmful.

The realm of alternative medicine is full of such opinions. They are personified by men who created therapies based on wishful thinking, fallacious assumptions, and pseudoscience. Many of the alternative modalities – therapies or diagnostic methods – that are today so surprisingly popular have been originated by one single person. This book is about these men. It is an investigation into their lives, ideas, pseudoscience, and achievements and an attempt to find out what motivated each of these individuals to create treatments that are out of line with the known facts.

The book is divided into two parts. The first section sets the scene by establishing what true discoveries in medicine might look like. It offers short biographical sketches of my personal choice of some of my ‘medical icons’. In addition, it provides the necessary background about the field of alternative medicine. The second section is dedicated to the often strange men who invented these bizarre alternative treatments and diagnostic methods. In this section, we discuss in some detail the life and work of these individuals. Moreover, we critically evaluate the evidence for and against each of these modalities. An finally, we attempt to draw some conclusions about the strange men who invented bizarre alternative methods.

Having studied alternative medicine for more than three decades and having published more scientific papers on this subject than anyone else, the individuals behind the extraordinary modalities have intrigued me for many years. By describing these eccentric men, their assumptions, motivations, delusions, and failures, I hope to offer both entertainment as well as information. Furthermore, I aim at promoting my readers’ ability to tell science from pseudoscience and at stimulating their capacity of critical thinking.

In contemporary healthcare, evidence-based practices are fundamental for ensuring optimal patient outcomes and resource allocation. Essential steps for conducting pharmacoeconomic studies in homeopathy involve study design, intervention identification, comparator selection, outcome measures definition, data collection, cost analysis, effectiveness analysis, cost-effectiveness analysis, cost-benefit analysis, sensitivity analysis, reporting, and peer review. While conventional medicine undergoes rigorous pharmacoeconomic evaluations, the field of homeopathy often lacks such scrutiny. However, the importance of pharmacoeconomic studies in homeopathy is increasingly recognized, given its growing integration into modern healthcare systems.

A systematic review was aimed at summarizing the existing economic evaluations of homeopathy. It was conducted by searching electronic databases (PubMed, Scopus, Web of Science) to identify relevant literature using keywords such as “homeopathy,” “pharmacoeconomics,” and “efficacy.” Articles meeting inclusion criteria were assessed for quality using established frameworks like the Consolidated Health Economic Evaluation Reporting Standards (CHEERS). Data synthesis was conducted thematically, focusing on study objectives, methodologies, findings, and conclusions.

Ten pharmacoeconomic studies within homeopathy were identified, demonstrating varying degrees of compliance with reporting guidelines. While most studies reported costs comprehensively, some lacked methodological transparency, particularly in analytic methods. Heterogeneity was observed in study designs and outcome measures, reflecting the complexity of economic evaluation in homeopathy. Quality of evidence varied, with some studies exhibiting robust methodologies while others had limitations.

The authors concluded that, based on the review, recommendations include promoting homeopathic clinics, providing policy support, adopting collaborative healthcare models, and leveraging India’s homeopathic resources. Pharmacoeconomic studies in homeopathy are crucial for evaluating its economic implications compared to conventional medicine. While certain studies demonstrated methodological rigor, opportunities exist for enhancing consistency, transparency, and quality in economic evaluations. Addressing these challenges is essential for informing decision-making regarding the economic aspects of homeopathic interventions.

The truth is that there are not many economic studies of homeopathy that are worth the paper they were printed on. One of the most rigorous analysis was published by German pro-homeopathy researcher. This study aimed to provide a long-term cost comparison of patients using additional homeopathic treatment (homeopathy group) with patients using usual care (control group) over an observation period of 33 months.

Health claims data from a large statutory health insurance company were analysed from both the societal perspective (primary outcome) and from the statutory health insurance perspective (secondary outcome). To compare costs between patient groups, homeopathy and control patients were matched in a 1:1 ratio using propensity scores. Predictor variables for the propensity scores included health care costs and both medical and demographic variables. Health care costs were analysed using an analysis of covariance, adjusted for baseline costs, between groups both across diagnoses and for specific diagnoses over a period of 33 months. Specific diagnoses included depression, migraine, allergic rhinitis, asthma, atopic dermatitis, and headache.

Data from 21,939 patients in the homeopathy group (67.4% females) and 21,861 patients in the control group (67.2% females) were analysed. Health care costs over the 33 months were 12,414 EUR [95% CI 12,022-12,805] in the homeopathy group and 10,428 EUR [95% CI 10,036-10,820] in the control group (p<0.0001). The largest cost differences were attributed to productivity losses (homeopathy: EUR 6,289 [6,118-6,460]; control: EUR 5,498 [5,326-5,670], p<0.0001) and outpatient costs (homeopathy: EUR 1,794 [1,770-1,818]; control: EUR 1,438 [1,414-1,462], p<0.0001). Although the costs of the two groups converged over time, cost differences remained over the full 33 months. For all diagnoses, homeopathy patients generated higher costs than control patients.

The authors concluded that their analysis showed that even when following-up over 33 months, there were still cost differences between groups, with higher costs in the homeopathy group.

SURPRISE, SURPRISE!!!

Homeopathy is not cost-effective.

How could it possibly be? To be cost-effective, a theraapy has to be first of all effective – and that homeopathy is certainly not.

So, why does the avove-cited new paper arrive at a more positive conclusion?

Here are some potential explanations:

The authors of this paper are affiliated to:

  1. PatilTech Hom Research Solution, Maharashtra, India.
  2. Samarth Homeopathic Clinic and Research Center, Maharashtra, India.

The paper was published in the largely unknown, 3rd class Journal of Pharmacoeconomics and Pharmaceutical Management.

Most importantly, the authors aknowledge that many of the primary studies had serious methodological problems. However, this did not stop them from taking their data seriously. As a result, we have here another example of the old and well-known rule of systematic reviews:

RUBBISH IN, RUBBISH OUT!

To answer the question posed in the title of this post:

Is homeopathy cost-effective?

NO

 

 

Yesterday, I received the email below. I almost deleted it because, at first glance, it looked like spam. Then I started reading it – perhaps you should do so too.

Dear Edzard Ernst,

We’d like to inform you that Research.com, a leading academic platform for researchers, has just released the 2024 Edition of our Ranking of Best Scientists in the field of Medicine.

We are sure you will be very happy to learn that you have ranked #819 in the world ranking and #86 in United Kingdom. You have also been recognized with our Medicine Leader Award for 2024. Congratulations!

The ranking is based on D-index (Discipline H-index) metric, which only includes papers and citation values for an examined discipline. The ranking includes only leading scientists with D-index of at least 70 for academic publications made in the area of Medicine.

The full world ranking is available here: https://www.research.com/scientists-rankings/medicine
The full ranking for United Kingdom is available here: https://www.research.com/scientists-rankings/medicine/gb

Feel free to also read an article summarizing the statistics and trends from our ranking here: https://research.com/careers/world-online-ranking-of-best-medicine-scientists-2024-report

Please accept our sincere congratulations. Being present in our ranking is definitely a great achievement for you and your university or research institution. Feel free to share and publicize your accomplishment in any way you see fit.

With Best Regards…

________________________

I am not sure how significant this all is. Nonetheless, I thought I share the email with my small fan club from my blog.

This prospective cohort study examined the effects of fish oil supplements on the clinical course of cardiovascular disease, from a healthy state to atrial fibrillation, major adverse cardiovascular events, and subsequently death.

The analysis is based on the UK Biobank study (1 January 2006 to 31 December 2010, with follow-up to 31 March 2021 (median follow-up 11.9 years)) including 415 737 participants, aged 40-69 years. Incident cases of atrial fibrillation, major adverse cardiovascular events, and death, identified by linkage to hospital inpatient records and death registries. Role of fish oil supplements in different progressive stages of cardiovascular diseases, from healthy status (primary stage), to atrial fibrillation (secondary stage), major adverse cardiovascular events (tertiary stage), and death (end stage).

Among 415 737 participants free of cardiovascular diseases, 18 367 patients with incident atrial fibrillation, 22 636 with major adverse cardiovascular events, and 22 140 deaths during follow-up were identified. Regular use of fish oil supplements had different roles in the transitions from healthy status to atrial fibrillation, to major adverse cardiovascular events, and then to death:

  • For people without cardiovascular disease, hazard ratios were 1.13 (95% confidence interval 1.10 to 1.17) for the transition from healthy status to atrial fibrillation and 1.05 (1.00 to 1.11) from healthy status to stroke.
  • For participants with a diagnosis of a known cardiovascular disease, regular use of fish oil supplements was beneficial for transitions from atrial fibrillation to major adverse cardiovascular events (hazard ratio 0.92, 0.87 to 0.98), atrial fibrillation to myocardial infarction (0.85, 0.76 to 0.96), and heart failure to death (0.91, 0.84 to 0.99).

The authors concluded that regular use of fish oil supplements might be a risk factor for atrial fibrillation and stroke among the general population but could be beneficial for progression of cardiovascular disease from atrial fibrillation to major adverse cardiovascular events, and from atrial fibrillation to death. Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements.

I must admit that I am slightly puzzled by this study and its findings. The authors clearly speak of the ‘role’ regular use of fish oil supplements has. This language implies a casual impact. Yet, what we have here are associations, and every 1st year medical student knows that

correlation is not causation.

Other things to note are that:

  • the associations are only very weak;
  • they go in opposite directions depending on the subpopulation that is examined,
  • there is no plausible mechanism of action to explain all this.

Collectively, these facts suggest to me that we are indeed more likely dealing here with a non-causal association and not a causal link. All the more surprising then that the (UK) press took up this paper in a major and occasionally alarmist fashion (the headline in THE TELEGRAPH was Revealed: How cod liver oil could be bad for your health). I learned of it by listening to the BBC headline news.

 

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