Cardiovascular
Associations Between Long-Term Methylmercury Exposure from Fish Consumption and Blood Pressure in Older Women Sally Thurston* Sally Thurston Gary Myers Matthew Conrad Shamlaye Emelyn Shroff JJ Strain Alison Yeates Emeir McSorley Maria Mulhern Edwin van Wijngaarden
Background: Fish contains many beneficial nutrients, but also contains methylmercury (MeHg), a known neurotoxicant at sufficiently high doses. Studies have reported beneficial effects of fish intake on blood pressure (BP) but whether MeHg alters this relationship is unclear.
Methods: We estimated associations of long-term fish intake and MeHg exposure on BP in a high fish-eating cohort of 608 middle-aged to older women (mean age in 2021: 58 years, range: 45-77 years). Their MeHg exposure and fish intake were determined at enrollment in 1990 as part of the Seychelles Child Development Cohort and again in 2013 and 2021. Maternal fish intake (number of fish dishes consumed) was obtained from questionnaires and MeHg was measured in hair. A long-term average of each variable was estimated as the mean over the three time periods. Associations of fish and MeHg with systolic and diastolic BP in 2021 were estimated from linear regression in separate, joint and interaction models adjusted for relevant covariates.
Results: Mean fish intake was 10.4 dishes/week (range: 3.0 – 24.0) and mean MeHg was 6.93 ppm (range: 1.3-19.7). Each additional fish dish eaten was associated with 0.96 mmHg (95% CI: 0.42, 1.50) increase in systolic BP and 0.50 mmHg (95% CI: 0.18, 0.81) increase in diastolic BP without adjustment for MeHg; associations were similar with MeHg adjustment. MeHg was not associated with systolic or diastolic BP, with or without adjustment for fish intake. In interaction models that allowed the fish intake slope to differ by tertile of estimated average MeHg, associations with fish intake were most adverse in the highest MeHg tertile. In the highest tertile each fish dish was associated with 1.89 mmHg (95% CI: 0.66, 3.11) increase in systolic BP and 0.82 mmHg (95% CI: 0.13, 1.51) increase in diastolic BP.
Discussion: Results suggest that eating many fish dishes with high average MeHg levels over many decades may be adversely associated with blood pressure.