case-control study

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How often have we seen it stated on this blog and elsewhere by enthusiasts of so-called alternative medicine (SCAM) that COVID vaccinations were useless or even harmful? Here is some rather compelling evidence that should make them think again.

This population based cohort study investigated the effectiveness of primary covid-19 vaccination (first two doses and first booster dose within the recommended schedule) against post-covid-19 condition (PCC).

All adults (≥18 years) participated from the Swedish Covid-19 Investigation for Future Insights (a Population Epidemiology Approach using Register Linkage (SCIFI-PEARL) project, a register based cohort study in Sweden) with covid-19 first registered between 27 December 2020 and 9 February 2022 (n=589 722) in the two largest regions of Sweden. Individuals were followed from a first infection until death, emigration, vaccination, reinfection, a PCC diagnosis (ICD-10 diagnosis code U09.9), or end of follow-up (30 November 2022), whichever came first. Individuals who had received at least one dose of a covid-19 vaccine before infection were considered vaccinated.

The primary outcome was a clinical diagnosis of PCC. Vaccine effectiveness against PCC was estimated using Cox regressions adjusted for age, sex, comorbidities (diabetes and cardiovascular, respiratory, and psychiatric disease), number of healthcare contacts during 2019, socioeconomic factors, and dominant virus variant at time of infection.

Of 299 692 vaccinated individuals with covid-19, 1201 (0.4%) had a diagnosis of PCC during follow-up, compared with 4118 (1.4%) of 290 030 unvaccinated individuals. Covid-19 vaccination with any number of doses before infection was associated with a reduced risk of PCC (adjusted hazard ratio 0.42, 95% confidence interval 0.38 to 0.46), with a vaccine effectiveness of 58%. Of the vaccinated individuals, 21 111 received one dose only, 205 650 received two doses, and 72 931 received three or more doses. Vaccine effectiveness against PCC for one dose, two doses, and three or more doses was 21%, 59%, and 73%, respectively.

The authors concluded that the results of this study suggest a strong association between covid-19 vaccination before infection and reduced risk of receiving a diagnosis of PCC. The findings highlight the importance of primary vaccination against covid-19 to reduce the population burden of PCC.

This study should make the anti-vaxers re-consider their views. Sadly, I have little hope that they will. If they don’t, they provide rational thinkers with yet further evidence that they are cultists who are beyond learning from compelling data.

Omega-3 fatty acids (fish oil) supplementation reduces the occurrence of cardiovascular disease (CVD) and CVD-related mortality in patients at high-risk of CVD and in patients with elevated plasma triglyceride level. Yet, some studies have found an increased risk of atrial fibrillation (AF). AF is the most common sustained cardiac arrhythmia worldwide. It is associated with high morbidity and mortality rates and significant public health burden. Previous studies of the effect of omega-3 fatty acids on AF occurrence have reported contradictory results.

This review evaluated the effect of omega-3 fatty acids on the risk of AF. The results suggest that omega-3 fatty acids supplementation is associated with increased AF risk, particularly in trials that used high doses. Therefore, several factors should be considered before prescribing omega-3 fatty acids, including their dose, type, and formulation (fish, dietary fish oil supplements, and purified fatty acids), as well as patient-related factors and atrial mechanical milieu. Because the benefits of omega-3 fatty acids are dose-dependent, the associated AF risk should be balanced against the benefit for CVD. Patients who take omega-3 fatty acids, particularly at high doses, should be informed of the risk of AF and followed up for the possible development of this common and potentially hazardous arrhythmia.

Another recent review included 54,799 participants from 17 cohorts. A total of 7,720 incident cases of AF were ascertained after a median 13.3 years of follow-up. In multivariable analysis, EPA levels were not associated with incident AF, HR per interquintile range (ie, the difference between the 90th and 10th percentiles) was 1.00 (95% CI: 0.95-1.05). HRs for higher levels of DPA, DHA, and EPA+DHA, were 0.89 (95% CI: 0.83-0.95), 0.90 (95% CI: 0.85-0.96), and 0.93 (95% CI: 0.87-0.99), respectively.

The authors concluded that in vivo levels of omega-3 fatty acids including EPA, DPA, DHA, and EPA+DHA were not associated with increased risk of incident AF. Our data suggest the safety of habitual dietary intakes of omega-3 fatty acids with respect to AF risk. Coupled with the known benefits of these fatty acids in the prevention of adverse coronary events, our study suggests that current dietary guidelines recommending fish/omega-3 fatty acid consumption can be maintained.

Faced with contradictory results based on non-RCT evidence, we clearly need an RCT. Luckily such a trial has recently been published. It was an ancillary study of a 2 × 2 factorial randomized clinical trial involving 25 119 women and men aged 50 years or older without prior cardiovascular disease, cancer, or AF. Participants were recruited directly by mail between November 2011 and March 2014 from all 50 US states and were followed up until December 31, 2017.

Participants were randomized to receive EPA-DHA (460 mg/d of EPA and 380 mg/d of DHA) and vitamin D3 (2000 IU/d) (n = 6272 analyzed); EPA-DHA and placebo (n = 6270 analyzed); vitamin D3 and placebo (n = 6281 analyzed); or 2 placebos (n = 6296 analyzed). The primary outcome was incident AF confirmed by medical record review.

Among the 25 119 participants who were randomized and included in the analysis (mean age, 66.7 years; 50.8% women), 24 127 (96.1%) completed the trial. Over a median 5.3 years of treatment and follow-up, the primary end point of incident AF occurred in 900 participants (3.6% of study population). For the EPA-DHA vs placebo comparison, incident AF events occurred in 469 (3.7%) vs 431 (3.4%) participants, respectively (hazard ratio, 1.09; 95% CI, 0.96-1.24; P = .19). For the vitamin D3 vs placebo comparison, incident AF events occurred in 469 (3.7%) vs 431 (3.4%) participants, respectively (hazard ratio, 1.09; 95% CI, 0.96-1.25; P = .19). There was no evidence for interaction between the 2 study agents (P = .39).

The authors concluded that among adults aged 50 years or older, treatment with EPA-DHA or vitamin D3, compared with placebo, resulted in no significant difference in the risk of incident AF over a median follow-up of more than 5 years. The findings do not support the use of either agent for the primary prevention of incident AF.

So, does the regular supplementation with omega-3 fatty acids increase the risk of atrial fibrillation? The evidence is not entirely clear but, on balance, I conclude that the risk is low or even non-existent.

Conspiracy beliefs (CBs) can have substantial consequences on health behaviours by influencing both conventional and non-conventional medicine uptake. They can target powerful groups (i.e. upward CBs) or powerless groups (i.e. downward CBs). Considering their repercussions in oncology, it appears useful to understand how CBs are related to the intentions to use conventional and so-called alternative medicines (SCAM), defined as “medical products and practices that are not part of standard medical care” including practices
such as mind–body therapies, botanicals, energy healing or naturopathic medicine.

This paper includes two pre-registered online correlational studies on a general French population (Study 1 N = 248, recruited on social media Mage = 40.07, SDage = 14.78; 205 women, 41 men and 2 non-binaries; Study 2 N = 313, recruited on social media and Prolific, Mage = 28.91, SDage = 9.60; 154 women, 149 men and 10 non-binaries). the researchers investigated the links between generic and chemotherapy-related CBs and intentions to use conventional or SCAMs. Study 2 consisted of a conceptual replication of Study 1, considering the orientation of CBs.

Generic CBs and chemotherapy-related CBs appear strongly and positively correlated, negatively correlated with intentions to take conventional medicine and positively with intentions to take SCAM. The link between generic CBs and medication intention is fully mediated by chemotherapy-related CBs. When distinguished, upward CBs are a stronger predictor of chemotherapy-related CBs than downward CBs.

The authors concluded that the findings suggest that intentions to use medicine are strongly associated with CBs. This has several important implications for further research and practice, notably on the presence and effects of CBs on medication behaviours in cancer patients.

Sadly, the influence of CBs is not confined to the field of oncology but applies across all diseases and conditions. We have seen and discussed these issues in several previous posts, e.g.:

The most impressive evidence, however, is regularly being provided by some of the people who post comments on this blog. Collectively, this evidence has prompted me to postulate that SCAM itself can be seen as a consiracy theory.

Although bullshit is common in everyday life and has attracted attention from philosophers, its reception (critical or ingenuous) has not, to our knowledge, been subject to empirical investigation. Pseudo-profound bullshit consists of seemingly impressive assertions that are presented as true and meaningful but are actually vacuous.

In this study, researchers presented participants with bullshit statements consisting of buzzwords randomly organized into statements with syntactic structure but no discernible meaning (e.g., “Wholeness quiets infinite phenomena”). Across multiple studies, the propensity to judge bullshit statements as profound was associated with a variety of conceptually relevant variables (e.g., intuitive cognitive style, supernatural belief). Parallel associations were less evident among profundity judgments for more conventionally profound (e.g., “A wet person does not fear the rain”) or mundane (e.g., “Newborn babies require constant attention”) statements.

The authors concluded that these results support the idea that some people are more receptive to this type of bullshit and that detecting it is not merely a matter of indiscriminate skepticism but rather a discernment of deceptive vagueness in otherwise impressive sounding claims. Our results also suggest that a bias toward accepting statements as true may be an important component of pseudo-profound bullshit receptivity.

Harry G Frankfurt published his delightful booklet ‘ON BULLSHIT‘ in 2005. Since then, the term ‘bullshit’ has become accepted terminology in philosophy and science. But what exactly is bullshit? Frankfurt explains that is something between a lie and a bluff, perhaps more like the latter than the former.

In another recent article, Fugelsang explains that the growing prevalence of misleading information (i.e., bullshit) in society carries with it an increased need to understand the processes underlying many people’s susceptibility to falling for it. He also reports two studies (N = 412) examining the associations between one’s ability to detect pseudo-profound bullshit, confidence in one’s bullshit detection abilities, and the metacognitive experience of evaluating potentially misleading information.

The results suggest that people with the lowest (highest) bullshit detection performance overestimate (underestimate) their detection abilities and overplace (underplace) those abilities when compared to others. Additionally, people reported using both intuitive and reflective thinking processes when evaluating misleading information. Taken together, these results show that both highly bullshit-receptive and highly bullshit-resistant people are largely unaware of the extent to which they can detect bullshit and that traditional miserly processing explanations of receptivity to misleading information may be insufficient to fully account for these effects.

I am sure that some of the discussions on this blog are excellent examples for people with low bullshit detection performance overestimating their detection abilities and overplacing those abilities.

Many community pharmacies in Switzerland provide so-called alternative medicine (SCAM) approaches in addition to providing biomedical services, and a few pharmacies specialise in SCAM. A common perception is that SCAM providers are sceptical towards, or opposed to, vaccination.

The key  objectives of this study were to examine the potential roles of biomedically oriented and SCAM-specialised pharmacists regarding vaccine counselling and to better understand the association between vaccine hesitancy and SCAM. The researchers thus conducted semistructured, qualitative interviews. Transcripts were coded and analysed using thematic analysis. Interview questions were related to:

  • type of pharmaceutical care practised,
  • views on SCAM and biomedicine,
  • perspectives on vaccination,
  • descriptions of vaccination consultations in community pharmacies,
  • and views on vaccination rates.

Qualitative interviews in three language regions of Switzerland (German, French and Italian). A total of 18 pharmacists (N=11 biomedically oriented, N=7  SCAM specialised) were invited.

Pharmacist participants expressed generally positive attitudes towards vaccination. Biomedically oriented pharmacists mainly advised customers to follow official vaccination recommendations but rarely counselled vaccine-hesitant customers. SCAM-specialised pharmacists were not as enthusiastic advocates of the Swiss vaccination recommendations as the biomedically oriented pharmacists. Rather, they considered that each customer should receive individualised, nuanced vaccination advice so that customers can reach their own decisions. SCAM-specialised pharmacists described how mothers in particular preferred getting a second opinion when they felt insufficiently advised by biomedically oriented paediatricians.

The authors concluded that vaccination counselling in community pharmacies represents an additional option to customers who have unmet vaccination consultation needs and who seek reassurance from healthcare professionals (HCPs) other than physicians. By providing individualised vaccination counselling to vaccine-hesitant customers, SCAM-specialised pharmacists are likely meeting specific needs of vaccine-hesitant customers. As such, research and implementation efforts should more systematically involve pharmacists as important actors in vaccination provision. SCAM-specialised pharmacists particularly should not be neglected as they are important HCPs who counsel vaccine-hesitant customers.

I must say that I find these conclusions odd, perhaps even wrong. Here are my reasons:

  • Pharmacists are well-trained healthcare professionals.
  • As such, they have ethical obligations towards their customers.
  • These obligations include behaving in a way that is optimal for the health of their customers and follows the rules of evidence-based practice.
  • This includes explaining to vaccine-hesitant customers why the recommended vaccinations make sense and advising them to follow the official vaccination guidelines.
  • SCAM-specialised pharmacist should ask themselves whether offering SCAM is in line with their ethical obligation to provide optimal care and advice to their customers.

I fear that this paper suggests that SCAM-specialised pharmacists might be a danger to the health of their customers. If that is confirmed, they should consider re-training, in my view.

Swedish researchers examined the relationship between cognitive ability and prompt COVID-19 vaccination using individual-level data on more than 700,000 individuals in Sweden.

The analyses were based on individual-level data from several administrative registers in Sweden. The study population consisted of all men and women who enlisted for military service in Sweden between 1979 and 1997. During this period, enlistment was mandatory for men the year they turned 18 or 19. Women could not enlist for military service before 1980 but were then allowed to do so on a voluntary basis.

The study population thus covered almost the entire population of Swedish men born between 1962 and 1979, in total 750,381, as well as the sample of women who enlisted during the period of 1980–1997, in total 2703. In addressing the role of confounders, the researchers analyzed the sub-sample of 6750 twin brothers (3375 twin-pairs) in the enlistment records (identified by shared biological mother and year and month of birth).

The results show a strong positive association between cognitive ability and swift vaccination, which remained even after controlling for confounding variables with a twin-design. Consistent with this, the researchers showed that simplifying the vaccination decision through pre-booked vaccination appointments alleviates almost all of the inequality in vaccination behavior.

The authors concluded that the complexity of the vaccination decision may make it difficult for individuals with lower cognitive abilities to understand the benefits of vaccination.

On this blog, we have repeatedly discussed similar or related findings, e.g.:

I know, it would be politically incorrect, unkind, unhelpful, etc. but is anyone not tempted to simplify the issue by assuming that people who are against (COVID) vaccinations are intellectually challenged?

The KFF provides reliable, accurate, and non-partisan information to help inform health policy in the US. The KFF has just released its ‘Health Misinformation Tracking Poll Pilot‘ examining the public’s media use and trust in sources of health information and measuring the reach of specific false and inaccurate claims surrounding three health-related topics: COVID-19 and vaccines, reproductive health, and gun violence. It makes grimm reading indeed. Here are but a few excerpts pertaining to health/vaccination:

Health misinformation is widespread in the US with 96% of adults saying they have heard at least one of the ten items of health-related misinformation asked about in the survey. The most widespread misinformation items included in the survey were related to COVID-19 and vaccines, including that the COVID-19 vaccines have caused thousands of deaths in otherwise healthy people (65% say they have heard or read this) and that the MMR vaccines have been proven to cause autism in children (65%).

Regardless of whether they have heard or read specific items of misinformation, the survey also asked people whether they think each claim is definitely true, probably true, probably false, or definitely false. For most of the misinformation items included in the survey, between one-fifth and one-third of the public say they are “definitely” or “probably true.” The most frequently heard claims are related to COVID-19 and vaccines.

Uncertainty is high when it comes to health misinformation. While fewer than one in five adults say each of the misinformation claims examined in the survey are “definitely true,” larger shares are open to believing them, saying they are “probably true.” Many lean towards the correct answer but also express uncertainty, saying each claim is “probably false.” Fewer tend to be certain that each claim is false, with the exception of the claim that more people have died from the COVID-19 vaccines than from the virus itself, which nearly half the public (47%) recognizes as definitely false.

Across the five COVID-19 and vaccine related misinformation items, adults without a college degree are more likely than college graduates to say these claims are definitely or probably true. Notably, Black adults are at least ten percentage points more likely than White adults to believe some items of vaccine misinformation, including that the COVID-19 vaccines have caused thousands of sudden deaths in otherwise healthy people, and that the MMR vaccines have been proven to cause autism in children. Black (29%) and Hispanic (24%) adults are both more likely than White adults (17%) to say that the false claim that “more people have died from the COVID-19 vaccine than have died from the COVID-19 virus” is definitely or probably true. Those who identify as Republicans or lean towards the Republican Party and pure independents stand out as being more likely than Democratic leaning adults to say each of these items is probably or definitely true. Across community types, rural residents are more likely than their urban and suburban counterparts to say that some false claims related to COVID vaccines are probably or definitely true, including that the vaccines have been proven to cause infertility and that more people have died from the vaccine than from the virus.

Educational attainment appears to play a particularly important role when it comes to susceptibility to COVID-19 and vaccine misinformation. Six in ten adults with college degrees say none of the five false COVID-19 and vaccine claims are probably or definitely true, compared to less than four in ten adults without a degree. Concerningly, about one in five rural residents (19%), adults with a high school education or less (18%), Black adults (18%), Republicans (20%), and independents (18%) say four or five of the false COVID-19 and vaccine misinformation items included in the survey are probably or definitely true.


If you have followed some of the comments on this blog, you might find it hard to be surprised!

I do encourage you to read the full article.

This study aimed to clarify the psychological mechanism by which individuals accept health misinformation from social media and how health misperceptions affect subsequent unhealthy behavior in the context of dewormer use.

An online survey was conducted with 307 South Korean adults exposed to dewormer use information on social media. The positive association between the respondents’ uncertainty about their health and factual misbeliefs about dewormer use was moderated by their pre-existing attitude toward so-called alternative medicine (SCAM) vs. standard treatments, suggesting that individuals who are uncertain but more favorable toward SCAM tend to accept factual misbeliefs more easily. Individuals’ uncertainty about their health and treatment for the health management was positively associated with conspiracy beliefs. Factual misbeliefs were the key mediator in the association between the interaction of uncertainty and pre-existing attitude toward SCAM vs. standard treatments and dewormer-taking intention.


Image result for misinformation, cartoon

This is a subject that we have discussed many times before. See, for instance, here:

In my view, it is hugely important. Consumers who are uncertain, easily misled, convinced that ‘the establishment’ is against them, or prone to other conspiracy theories tend to be the ones that also fall easily for the lies of SCAM promoters. Indeed, I have previously suggested that SCAM itself is a conspiracy theory in disguise. Anyone who has been following the comment sections on this blog will find more evidence for this theory than he had ever needed, I fear.

It is clear to me that misinformation undermines not just evidence-based medicine but – much more dangerous -rationality in general. It would be thus urgent to do something about it.

But what?

In my view, the answer is to promote critical thinking. This, of course, is what I am aiming at with my blog. But my effort is merely a drop in the ocean. What we need is a systematic promotion of critial thinking on a much larger scale. It has to start at school and should be followed through to post-graduate education and beyond.

Such a strategy would require a very broad backing, not least on the political levels. And this is where the concept runs into insurmountable difficulties: politcians might not want us to be critical thinkers! This could enable the public to realize what often dismally poor jobs they might be up to.

Vaccine hesitancy has become a threat to public health, especially as it is a phenomenon that has also been observed among healthcare professionals. In this study, an international team of researchers analyzed the relationship between endorsement of so-called alternative medicine (SCAM) and vaccination attitudes and behaviors among healthcare professionals, using a cross-sectional sample of physicians with vaccination responsibilities from four European countries: Germany, Finland, Portugal, and France (total N = 2,787).

The results suggest that, in all the participating countries, SCAM endorsement is associated with lower frequency of vaccine recommendation, lower self-vaccination rates, and being more open to patients delaying vaccination, with these relationships being mediated by distrust in vaccines. A latent profile analysis revealed that a profile characterized by higher-than-average SCAM endorsement and lower-than-average confidence and recommendation of vaccines occurs, to some degree, among 19% of the total sample, although these percentages varied from one country to another: 23.72% in Germany, 17.83% in France, 9.77% in Finland, and 5.86% in Portugal.

The authors concluded that these results constitute a call to consider health care professionals’ attitudes toward SCAM as a factor that could hinder the implementation of immunization campaigns.

In my view, this is a very important paper. It shows what we on this blog have discussed often before: there is an association between SCAM and vaccination hesitancy. The big question is: what is the nature of this association. There are several possibilities:

  1. It could be coincidental. I think this is most unlikely; too many entirely different investigations have shown a link.
  2. It could mean that people start endorsing SCAM because they are critical about vaccination.
  3. It could be that people are critical about vaccination because they are proponents of SCAM.
  4. Finally, it could be that some people have a mind-set that renders them simultaneously hesitant about vaccination and fans of SCAM.

This study, like most of the other investigationson this subject, was not desighned to find out which possibility is most likely. I suspect that the latter two explanations apply both to some extend. The authors of this study argue that that, “from a theoretical point of view, this situation may be explicable by reasons that are both implicit (i.e., CAM would fit better with certain worldviews and ideological standpoints that conflict with the epistemology and values that underlies scientific knowledge) and explicit (i.e., some CAM techniques are doctrinally opposed to the use of vaccines). Although we have outlined these potential explanations for the observed relationships, more research is needed to better understand the underlying mechanisms”.


Online misinformation is disproportionality created and spread by people with extreme political attitudes, especially among the far-right. There is a debate in the literature about why people spread misinformation and what should be done about it. According to the purely cognitive account, people largely spread misinformation because they are lazy, not biased. According to a motivational account, people are also motivated to believe and spread misinformation for ideological and partisan reasons. To better understand the psychological and neurocognitive processes that underlie misinformation sharing among the far-right, an international team of researchers conducted a cross-cultural experiment with conservatives and far-right partisans in the Unites States and Spain (N = 1,609) and a neuroimaging study with far-right partisans in Spain (N = 36).

Far-right partisans in Spain and U.S. Republicans who highly identify with Trump were more likely to share misinformation than center-right voters and other Republicans, especially when the misinformation was related to sacred values (e.g., immigration). Sacred values predicted misinformation sharing above and beyond familiarity, attitude strength, and salience of the issue. Moreover, far-right partisans were unresponsive to fact-checking and accuracy nudges. At a neural level, this group showed increased activity in brain regions implicated in mentalizing and norm compliance in response to posts with sacred values.

The authors concluded that these results suggest that the two components of political devotion – identity fusion and sacred values – play a key role in misinformation sharing, highlighting the identity-affirming dimension of misinformation sharing. We discuss the need for motivational and identity-based interventions to help curb misinformation for high-risk partisan groups.

People who have followed the discussions on this blog closely could be forgiven in assuming that right-wing political devotion also plays an important role in spreading misinformation about healthcare (e.g. vaccination) and so-called alternative medicine (SCAM). It would be good, if someone could test this hypothesis more directly.


Just as I had finished writing this post, I came across a quote given yesterday by Ben Habib on GBN:

“I’m very reluctant to put my destiny in the hands of scientists. You know, unbridled authority given to faux knowledge.”


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