Impact of urinary cadmium on mortality in the Japanese general population in cadmium non-polluted areas.
The aim of the present study was to evaluate the dose-effect relationship between urinary cadmium (U-Cd as an index of internal Cd exposure) and mortality in a cohort of the Japanese general population. A 19-year cohort study was conducted in 897 men and 1307 women who lived in two non-polluted areas in Japan. The subjects were categorized into four quartiles based on creatinine adjusted U-Cd (μg/g cre). Hazard ratio (HR) and 95% confidence interval (95%CI) of the quartiles of U-Cd for mortality was calculated using a proportional hazards regression. Forward stepwise model selection was applied to the potential covariates such as age, body mass index, mean arterial pressure, various lifestyle factors and present illness. The mortality rates per 1000 person years were 27.8 and 12.5 in men and women, respectively. In men, the fourth quartile of U-Cd (≥ 2.919 μg/g cre) showed a significant, positive HR (1.50, 95%CI: 1.11-2.02) for mortality compared to the first quartile (< 1.014). In women, the fourth quartile of U-Cd (≥ 3.943 μg/g cre) also showed a significant HR (1.50, 95%CI: 1.08-2.09) for mortality compared to the first quartile (< 1.140). The present study clarified that U-Cd was significantly associated with increased mortality, indicating the worsened life prognosis of the general population in Cd non-polluted areas in Japan. These results highlight the importance of further discussion of the health risk assessment of Cd exposure in the general population.