Association between social group participation and perceived health among elderly inhabitants of a previously methylmercury-polluted area.

OBJECTIVE: This study attempted to clarify the association between participation in a social group and perceived health among elderly residents of a previously methylmercury-polluted area in Japan. METHODS: We conducted a cross-sectional study using eligible subjects from the Shiranui Sea coastal area, where mercury poisoning due to daily intake of fish and shellfish had previously caused some residents to develop the neurological disorder "Minamata disease (MD)." In the present study, we selected subjects aged ≥65 years who had never been diagnosed with MD or applied for medical treatment compensation. RESULTS: A logistic regression model after adjusting for confounding factors showed that membership in a hobby or volunteer group was associated with good perceived health (odds ratio 1.97, 95 % confidence interval 1.02-3.80). CONCLUSION: Our results showed that the effects of membership in social groups on perceived health were not equal across all social groups, with only hobby- or volunteer-related groups having a positive effect on perceived health. Our findings suggested that promoting participation in a social group such as hobby- or volunteer-related groups can help improve perceived health among elderly individuals who had experienced environmental pollution incidents.

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

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.

[Association between Minamata disease status and activities of daily living among inhabitants in previously methylmercury-polluted areas].

OBJECTIVES: Minamata disease (MD), first discovered in 1956, is a neurological disorder caused by mercury poisoning due to daily intake of fish and shellfish that have been contaminated by methylmercury discharged from chemical factories. However, reports of ill health increased sharply following the 2004 Supreme Court ruling instructing the Japanese government to pay damages to MD patients. We examined the distribution of disability in activities of daily living (ADL), and the association between MD status in terms of compensation system and ADL disability among the general population of previously methylmercury-polluted areas. METHODS: Data were collected by two-stage stratified sampling of residents 40-79 years old in 172 postal-code areas on the Shiranui Sea coast, the endemic area of MD. Questionnaires were distributed to eligible subjects (n = 2100) and collected at a later visit or by mail. Information on demographic factors, basic ADL (BADL), and instrumental ADL (IADL) was obtained using questionnaires. We performed logistic regression analysis to assess the relationship between MD status in terms of compensation system and ADL disability. RESULTS: We classified the 1422 residents who completed the questionnaire in accordance with their MD status in terms of compensation system: Early (those who received MD compensation before the Supreme Court decision), Recent (those who applied for compensation after the Supreme Court decision), Not Yet (those who have not yet applied for compensation, but have health-related anxieties about MD effects), and Normal (those who have not applied for compensation, and do not have health-related anxieties about MD effects). Adjusting for confounding factors, MD status was significantly associated with the disability grades of BADL and IADL with an increasing trend in the order of Normal, Not Yet, Recent, and Early. The odds ratios (95% CI) based on Normal were 2.08 (1.08-4.01), 3.87 (2.14-7.01), and 4.50 (2.66-7.61) for BADL and 2.41 (1.62-3.61), 3.20 (2.12-4.85) and 3.68 (2.52-5.38) in Not Yet, Recent, and Early for IADL, respectively. CONCLUSION: Early, Recent, and Not Yet had lower ADL grades than Normal. Moreover, the population with a low ADL grade and health-related anxieties had increased throughout the previously methylmercury-polluted areas. The issue of ill health among populations living in previously methylmercury-polluted areas should be addressed in the wider context of public and community health.