Associations of fish oil supplementation with incident dementia: Evidence from the UK Biobank cohort study, 2022, Yan Huang et al

Background: Although numerous studies have investigated the association of dietary intake of omega-3 fatty acids with cognitive function and the risks of dementia, the relationship between fish oil supplementation and incident dementia in a large population-based cohort study has not yet well studied.

Materials and methods: A total of 211,094 community-dwelling older persons over 60 years from the UK Biobank cohorts enrolled between 2006 and 2010 that reported regularly taking fish oil and had no dementia at baseline, was included in the present study. All participants completed an electronic questionnaire regarding habitual use of supplements including fish oil.

Results: Overall, 83,283 (39.5%) participants reported regularly taking fish oil at baseline. Of 211,094 participants with the median age was 64.1 years, 5,274 participants developed dementia events during a median follow-up of 11.7 years, with 3,290 individuals derived from fish oil non-users. In the multivariable adjusted models, the adjusted hazard ratios (HRs) associated with fish oil supplementation for all-cause dementia, vascular dementia, frontotemporal dementia, and other dementia were 0.91 [CI = 0.84–0.97], 0.83 [CI = 0.71–0.97], 0.43 [CI = 0.26–0.72], 0.90 [CI = 0.82–0.98], respectively (all P < 0.05). However, no significant association between fish oil supplementation and Alzheimer’s disease was found (HR = 1.00 [CI = 0.89–1.12], P = 0.977). In the subgroup analyses, the associations between use of fish oil and the risk of all-cause dementia (P for interaction = 0.007) and vascular dementia were stronger among men (P for interaction = 0.026).

Conclusion: Among older adults, regular fish oil supplementation was significantly associated with a lower risks of incident all-cause dementia, as well as vascular dementia, frontotemporal dementia and other dementia but not Alzheimer’s disease. These findings support that habitual use of fish oils may be beneficial for the prevention of dementia in clinical practice.

https://www.frontiersin.org/articles/10.3389/fnins.2022.910977/full

 

I think that fish oil may increase risk for certain cancers like prostate, don’t quote me on that though.

 

This looks like the Fire Alarm effect. People who deliberately choose to install a Fire Alarm in their homes are very unlikely to have a house fire, simply because they are diligent about the threat from fire and installing an alarm is an integral part of that diligence; meaning cause and protective effect are circular confounds.

Taking a supplement as a personal choice is evidence of diligence around health concern which almost certainly is reflected in other health maintaining behaviours which are not accounted for in the covariate measures available in the UK Biobank data. Despite their positive view of the use of fish oil, the authors do acknowledge the limitations of their study:

"Baseline characteristics of the participants stratified by fish oil supplementation status (non-users vs. users) were presented in Table 1. Totally, 111,583 (52.9%) participants were female, 205,193 (97.2%) were white and 81,444 (38.6%) had college or above education level, with a mean (SD) age of 64.1 (2.9) years. Of 211,094 participants, 83,283 (39.5%) reported regularly take fish oil at baseline. Compared with the fish oil non-users, fish oil users were older, more likely to be female, no current drinkers, current smokers, physically active, and had less BMI (all P < 0.001). Furthermore, fish oil users had higher frequency of oily fish intake and had lower prevalence of hypertension and diabetes than non-users (all P < 0.001). Likewise, fish oil users were more likely to take aspirin, mineral and other dietary supplementations, and had lower percentage of using antihypertensive drug and lipid lowering medication than the non-users (all P < 0.001)."

"There were several potential limitations in the present study. First, the study participants were simply stratified by fish oil uses or no-users according to an electronic questionnaire at baseline, lacking of detailed information of fish oil supplements such as formulation, dose and using duration. Therefore, it is difficult to evaluate dose-response associations between fish oil supplementation and incident dementia. Second, although a series of known potential confounders has been adjusted in our analyses, we cannot completely exclude the possibility of residual confounders in the present study. Third, it is difficult to distinguish the effects of a healthy lifestyle from the habitual use of fish oil supplements in determining risks of dementia in an observational study. Fourth, these results cannot be generalized to other ethnic populations since a considerable proportion (97.2%) of participants in UK Biobank cohort is white people. Fifth, the relatively low response rate (5.45% of 9,238,453 invited individuals) that consented to join the study cohort might have contributed to selection bias and underestimation of dementia incidence (Fry et al., 2017). Finally, misclassification of exposure remains a possibility while the overall accuracy of obtaining data is good, which is likely to have biased these findings (Lourida et al., 2019)."

 

Did they test these 211,094 community-dwelling older persons over 60 years to see if their omega 3 fatty acid was deficient?

My Omega 3 level was way below normal when I had an RBC fatty acid test done in 2001. I could barely follow instructions and would forget simply things, like paying for something and then leaving w/o it. I made a huge improvement once I started taking fish oils and have been taking them ever since.