Eating Fish is Associated with Decreased All-Cause Mortality in Older Adults

Mozaffarian and his colleagues published a paper recently in the Annals of Internal Medicine analyzed data from 2692 U.S. adults aged 74 years (±5 years) without prevalent cardiovascular diseases at baseline, who participated in the National Heart, Lung, and Blood Institute (NHLBI)-funded cohort, The Cardiovascular Health Study (CHS). The investigators measured the blood circulating levels of 3 types of long-chain omega-3 polyunsaturated fatty acids (omega-3 PUFAs); eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). These were measured from the blood that was collected from the participants in 1992. They then followed them longitudinally for 16 years (1992 through 2008) to evaluate the relationship with total and cause-specific mortality and incident fatal or nonfatal CHD and stroke.

The authors found that the individual levels of EPA, DPA, and DHA, and their total levels (omega-3 PUFA) were associated with lower total mortality across three robust models of adjusted Cox proportional hazards models (age, gender, various demographic and co-morbid conditions, and dietary factors):

       The participants in the higher quintile of the total omega-3 PUFAs had 27% lower risk 

       The participants in the higher quintile of EPA had 17% lower risk 

       The participants in the higher quintile of DPA had 23% lower risk

       The participants in the higher quintile of DHA had 20% lower risk

All results were statistically significant with narrow 95% confidence internals.

For cause-specific mortality, and using the same adjustment models of the total mortality risk data, total omega-3 PUFAs, and most of the individual levels of the three subtypes, were associated with cause-specific mortality. Total omega-3 PUFAs was associated with: 

       35% lower risk from cardiovascular mortality

       40% lower risk from coronary heart disease mortality

       45% lower risk from arrhythmic coronary heart disease (CHD) mortality

       28% lower risk from non-arrhythmic CHD mortality

       40% lower risk from stroke mortality

       28% lower risk from total fatal and nonfatal CHD mortality

       17% lower risk from nonfatal myocardial infarction mortality

       25% lower risk from total fatal and nonfatal stroke mortality

       37% lower risk from Ischemic stroke mortality

This data strongly suggests that fish consumption or fish oil supplementation would reduce both total mortality and cause-specific mortality in older adults. The steepest dose-response relationship between the circulating blood levels of omega-3 PUFAs and the decreased risk came from as low as 400 mg per day dietary intake, or two servings of fatty fish per week. This will lead to an average increase of about 2 more years of life in those with higher levels compared to those with lower levels.

My opinion:

This conclusion is supported by the robust statistical analyses with adjustment to many confounders, as well as a quantification of the omega-3 PUFAs rather than the amount of fish intake from Food Frequency Questionnaires (FFQ) or similar tool. Despite some limitations in this paper, it is a landmark paper in supporting increased fish intake to decrease the risk of mortality in older adults. 

Does Epidemiology Matter?

Dr. Michael Lauer, the director of the Division of Cardiovascular Sciences at the National Heart, Lung, and Blood Institute (NHLBI), recently wrote an editorial in JAMA¹ calling for “creative transformation” of epidemiology research in the United States.  He states:

“…Yet today, despite these extraordinary contributions, the value of epidemiology is questioned. Critics cite excess expense, repudiated findings, studies that offer small incremental knowledge, inability to innovate at reasonable cost, and failure to identify research questions with the greatest merit. At a time of unprecedented budgetary constraints, these critics wonder what epidemiology has done for medical science lately…”.  

Dr. Lauer's comments are crucial especially with the recent budget sequestration to limit United States' federal spending to meet the deficit targets that will likely affect the already decreased funding medical research from the National Institutes of Health (NIH). NIH Director, Dr. Francis Collins, MD, PhD, stated that the NIH already lost 20% of its purchasing power for medical research. Furthermore, such cuts will force the NIH to fund 2300 fewer grants in 2013. Such automatic cuts will be "devastating". Of course I don't have to mention the accompanying economic crisis worldwide. 

Dr. Lauer sums the needed actions into the following key elements:

“… Such transformations will likely include refocused scientific questions, centralized and integrated governance, different types of exposure and outcome measures, and embedded clinical and policy trials…”  

The driving passion behind initiating this academic epidemiology blog is to discuss the latest findings from epidemiologic research of mainly non-communicable diseases that would be of interest to epidemiologists, epidemiologists-in-training, and practicing physicians. Our main focus will be directed towards discussing groundbreaking findings that affects clinical practice, policy-making and lifestyle. 

Dr. Lauer concluded his JAMA editorial: 

“These transformations will also ensure that epidemiology will have much to give, whether lately or later.”

I am sure we will!


References:

1.       Lauer, M. S. (2012) Time for a creative transformation of epidemiology in the United States.   JAMA 308, 1804-1805