Causes of death in Minamata disease: analysis of death certificates

Abstract

The causes of death in Minamata disease were analyzed and compared with those of control subjects. Of the 1422 Minamata disease patients in the Kumamoto Prefecture, 378 had died by the end of 1980. Of these 378, the first death occurred in 1954 with a peak incidence in 1956 when Minamata disease was officially reported for the first time. The number of deaths increased rapidly after 1972 with a second peak in 1976. The male:female ratio was 1.8:1 and the mean age-at-death was 67.2 years (SD = +/- 18.65). The mean age-at-death was younger in the cases of the initial outbreak than in those recently. There were, on the average, 2.8 causes of death per person. Of these cases, 157 (41.5%) had Minamata disease indicated on the death certificate, though 64 (16.9%) had Minamata disease coded as the underlying cause. Minamata disease and the noninflammatory diseases of the central nervous system (CNS) were the main underlying causes of death between 1954 and 1969, while, in the multiple cause data, pneumonia and non-ischemic heart disease were the most prevalent. Cerebrovascular diseases (18.0%) were the main underlying causes of death followed by malignant neoplasms (14.7%), cardiovascular diseases (14.1%) and Minamata disease (14.1%) in 1970 or later, while cardiovascular diseases (18.6%), Minamata disease (14.5%), cerebrovascular diseases (10.4%) and malignant neoplasms (7.1%) were the major multiple causes of death. As compared with the control, the proportions of deaths due to noninflammatory diseases of CNS and pneumonia were higher in the initial outbreak. Although the difference in the causes of death was less apparent recently, malignant neoplasms and hypertensive diseases tended to be lower. These results suggest that there is a need for a long-term follow-up of Minamata disease patients. The data also show the potential value of multiple causes of death coding in analyses of mortality.

Dietary fats altered nephrotoxicity profile of methylmercury in rats

“…In humans, MeHg caused fatty degeneration of renal epithelial cells (Takeuchi, 1970). The standardized mortality ratios for nephritis, nephrosis and nephrotic syndrome were significantly higher in the female patients with Minamata disease, a disease occurring mainly among fisherman and their families who repeatedly consume fish contaminated with MeHg, compared with the general population (Tamashiro et al, 1984(Tamashiro et al, , 1986. A very recent study conducted in Japan revealed a positive correlation between urinary N-acety-β-D-glucosaminidase (NAG) activity and α-microglobulin (AMG), a measure of renal tubule function, and daily mercury intake and mercury levels in hair, toenails and urine in women free from occupational exposures .…”

Organic mercury compounds: human exposure and its relevance to public health

“…D eath resulting from organic mercury ingestion has been well documented following outbreaks of poisoning after consumption of methylmercury-contaminated fish in M inamata, Japan (Tsubaki and Takahashi, 1986) and consumption of grains contaminated with methylmercury and ethylmercury in Iraq (Bakir et al, 1973; Al-Saleem and the Clinical Committee on M ercury Poisoning, 1976). A case-control study comparing the cause of death for patients with M inamata disease with the cause of death in unexposed persons showed that in deaths prior to 1970, M inamata patients had significantly increased noninflammatory diseases of the nervous system compared with unexposed persons (Tamashiro et al, 1984). Pneumonia and nonischemic heart disease were reported as prominent secondary causes of death in the exposed group.…”

Age standardized cancer mortality ratios in areas heavily exposed to methyl mercury

“…Some studies in Minamata investigated the relationship between MeHg and malignant neoplasms (Tamashiro et al 1984(Tamashiro et al , 1985(Tamashiro et al , 1986Futatsuka et al 1987;Kinjo et al 1996), and found positive correlations with liver cancer and leukemia (Tamashiro et al 1986;Kinjo et al 1996). However, there were many problems in the study designs.…”

“…However, there were many problems in the study designs. In four studies (Tamashiro et al 1984(Tamashiro et al , 1985Futatsuka et al 1987;Kinjo Fig. 1 Map of the Shiranui Sea.…”