Relationships Between Percentage of Forest Coverage and Standardized Mortality Ratios (SMR) of Cancers in all Prefectures in Japan

To explore whether forest coverage affects the rate of deaths due to cancers in Japan, we investigated the relationships between the percentage of forest coverage and standardized mortality ratios due to cancers in all prefectures in Japan.

Data on the percentage of forest coverage in all prefectures in Japan were collected from the database of the Forestry Agency of Japan. Data on standardized mortality ratios (SMR) due to lung, stomach, kidney, and colon cancers in males and females, breast and uterine cancers in females, and prostate cancer in males, and data of smoking status of males and females in all prefectures in Japan were collected from the database of the Ministry of Health, Labour, and Welfare of Japan. Human development index (HDI) was used as a parameter of the socioeconomic status of each prefecture. The correlation and partial correlation coefficients between the percentage of forest coverage and SMR of cancers, after controlling for the effects of smoking and the socioeconomic status, were calculated.

People living in areas with lower forest coverage had significantly higher SMR of cancers compared with the people living in areas with higher forest coverage. There were significant inverse correlations between the percentage of forest coverage and the SMR of lung, breast, and uterine cancers in females, and the SMR of prostate, kidney, and colon cancers in males in all prefectures in Japan, even after the effects of smoking and socioeconomic status were factored in.

These findings indicate that increased forest coverage may partially contribute to a decrease in mortality due to cancers in Japan.