Association between early methylmercury exposure and functional health among residents of the Shiranui Sea communities in Japan

Abstract

The objective of this study was to evaluate the effect of estimated historical methylmercury exposure on the functional health of residents living in the Shiranui Sea communities in Japan. Functional health was measured by self-reported activities of daily living (ADL). Study areas were categorized into high, medium and low methylmercury exposure areas according to their location or distance from the Shiranui Sea. We estimated the adjusted prevalence odds ratios of impaired ADL in relation to exposure using a logistic regression model. Compared with residents in the low-exposure area, residents in the high-exposure area were significantly associated with a higher prevalence odds ratio (OR) for impaired ADL after adjustment for confounding factors (adjusted ORs = 2.8, 95% CI: 1.3–6.2). These results showed strong dose-response relationships (p for trend = 0.0050). Our findings suggest that historical methylmercury exposure might cause functional impairment in later in life depending on the exposure level.

Keywords:

• activities of daily living
• aging
• methylmercury
• Minamata disease
• Shiranui Study

Acknowledgements

We thank the participants of this survey and the staff of the Kumamoto and Kagoshima prefectures for providing the data of the Minamata disease patients per postal code area (ooaza), and the research assistants who participated in the field survey. We are especially grateful to Ms Kiyoko Fukumoto for assisting as an official staff member of the Shiranui Study Group throughout the entire process. This work was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (17203033).