Correlation of cerebrovascular disease standardized mortality ratios with dietary sodium and the sodium/potassium ratio among the Japanese population

Abstract

One thousand seventy-two 24-hr diet duplicate samples were collected from inhabitants of 49 regions in various parts of Japan during the winters of 1977–1981. An additional 238 samples were collected in an adjacent summer. The samples were analyzed for sodium (Na) and potassium (K) by flame atomic absorption spectrometry and for chloride (Cl) with a chloride counter. The winter-summer differences in Na, Cl, and Na/K were essentially negligible. When the regional means of Na, K, Cl, and Na/K were compared with the 1969–1978 standardized mortality ratios of each region, positive and significant correlations were observed between winter Na and the standardized mortality ratios for cerebrovascular disease ( P < 0.01), cerebral infarction ( P < 0.01), and subarachnoid hemorrhage ( P < 0.05) in both males and females. The correlation ( P < 0.01) with the cerebrovascular disease standardized mortality ratio was further confirmed by the values for 1978–1982. In the case of the Na/K ratio, the correlation with the standardized mortality ratio for each of the three diseases was significant for men ( P < 0.01 or 0.05, depending on the disease) but not for women ( P > 0.05). Both Na and Na/K showed significant associations with the ischemic heart disease standardized mortality ratio in men ( P < 0.05) but not in women ( P > 0.05). In contrast, no positive association was found between Na, K, Cl, or Na/K and standardized mortality ratios for diabetes mellitus, liver cirrhosis, tuberculosis, or liver cancer ( P > 0.05). Current blood pressure did not appear to correlate with any of the Na, K, Cl, or Na/K measurements. The validity of the present observation is discussed.