Population-wide reduction in dietary salt intake is likely the primary driver of decreased blood pressure and stroke mortality in Japan, contributing to its high longevity.
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Supports salt reduction for stroke prevention; leaves open generalizability beyond Japan's historical context.
Japan is one of the countries with the longest longevity in the world, and it was accomplished by a drastic decline in stroke mortality from 1960's. The decline in stroke mortality would be largely explained by a population-wide decreasing trend in blood pressure (BP) level, because higher BP has been the strongest risk factor of stroke; about 20% of total deaths can be explained by higher BP above optimal in Japan. Decreasing trend in BP occurred both in men and women in all age-groups, which cannot be fully explained by the widespread use of anti-hypertensive agents. The most probable reason for the population-wide BP decline in Japan would be a large decline in dietary salt intake after 1950's. However, other factors including obesity, high alcohol intake, and unfavorable dietary habits could increase BP level of Japanese again.
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Katsuyuki Miura (2011) studied this question.
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