Objective Long-chain omega-3 polyunsaturated fatty acids (PUFA) from fish have been inversely associated with coronary heart disease (CHD) risk. Fish may also contain methylmercury, which has been associated with higher CHD risk and may diminish the cardioprotective effect of long-chain omega-3 PUFA. We investigated the associations of serum long-chain omega-3 PUFA and hair mercury with the odds for myocardial ischaemia during exercise.
Methods A total of 2199 men from the Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42–60 years were studied in 1984–89. Of the 2199 men, 342 had history of CHD. The men performed a maximal symptom-limited exercise stress test using an electrically braked bicycle ergometer. ORs for exercise-induced myocardial ischaemia were estimated with logistic regression.
Results In the multivariable analysis, those in the highest versus lowest serum long-chain omega-3 PUFA quartile had 33% lower odds of myocardial ischaemia (OR 0.67, 95% CI 0.51 to 0.87, p-trend=0.006). The association was stronger among those with CHD history (OR 0.10, 95% CI 0.03 to 0.39, p-trend <0.001), than among those without (OR 0.80, 95% CI 0.57 to 1.12, p-trend=0.17) (p-interaction=0.01). Higher hair mercury concentration was associated with increased odds for myocardial ischaemia in the entire population (OR 1.62, 95% CI 1.22 to 2.14, p-trend=0.002).
Conclusion Higher circulating concentrations of the long-chain omega-3 PUFAs, a marker for fish consumption, were associated with lower occurrence of exercise-induced myocardial ischaemia, but only among men with CHD history. Hair mercury concentration was directly associated with the occurrence of exercise-induced myocardial ischaemia in the entire study population.
- polyunsaturated fatty acids
- exercise test
- myocardial ischemia
- population study
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Contributors BT, T-PT, SK, JS and JKV acquired the data and designed and conducted the research; BT analysed the data and drafted the manuscript; JKV had primary responsibility for the final content; T-PT, SK, JS and JKV critically revised the manuscript for important intellectual content and all authors read and approved the final manuscript.
Funding This study was funded by Kuopio University Foundation, Juho Vainio Foundation, and University of Eastern Finland. The KIHD project was funded by research grants to Jukka T. Salonen and George A. Kaplan from the NIH and the Academy of Finland.
Disclaimer The funding sources had no role in study design; in the collection, analysis and interpretation of data; in the writing of the report or in the decision to submit the article for publication.
Competing interests None declared.
Ethics approval The Kuopio Ischaemic Heart Disease Risk Factor Study protocol was approved by the Research Ethics Committee of the University of Kuopio.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Not required.