The rate of breast cancer in Western countries is 10 percent higher in the left breast than in the right. This also is true for the skin cancer melanoma.
Researchers have suggested a surprising explanation for this — and for the dramatic increase in rates of breast cancer and melanoma over the past three decades.
In Japan, there is no correlation between the rates of melanoma and breast cancer, and there is no left-side prevalence for either disease. The rate of breast cancer in Japan is also significantly lower than in the West.
This may be due to differences in sleeping habits in Japan and Western countries. Previous research has shown that people prefer to sleep on their right sides, possibly as a way of reducing weight stress on the heart.
This is most likely the same in both the East and the West, but the futons used for sleeping in Japan are mattresses placed directly on the bedroom floor, in contrast to the elevated box springs and mattress of beds used in the West.
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