Seasonal variation in mortality from ischemic heart disease and cerebrovascular disease in Okinawa and Osaka: the possible role of air temperature.

Okinawa is located in a subtropical area and is well-known for low mortality due to ischemic heart disease (IH-D) and cerebrovascular disease (CVD). However, the factors that contribute to these low mortality rates remain unclear. We examined the seasonal variation in the mortality due to IHD and CVD among Okinawa and Osaka residents, aged 45 to 84 years, between 1992 and 1996. In addition, we studied if there was a relationship between the monthly mortality rate from IHD or CVD and the monthly mean daily air temperature in Naha City and Osaka City. Data on the monthly mean daily air temperature was obtained from the meteorological stations in Naha City and Osaka City. Our results showed that there were inverse correlations between the monthly mean daily temperature in a city and each of the monthly mortality from IHD in Okinawa (r=-0.794, p<0.01), the monthly mortality from CVD in Okinawa (r=-0.837, p<0.001), and the monthly mortality from CVD in Osaka (r=-0.954, p<0.001). In Osaka, the monthly mortality rate from IHD was at or near its minimum value when the mean daily temperature was approximately 25 degrees C (in September), and it increased in a linear fashion as the mean monthly temperature fell (r=-0.975, p<0.001). The difference between the monthly mortality from IHD or CVD among the Okinawa and the Osaka residents increased in the winter season in comparison with that in the other seasons, with the exception for IHD in July and in August. These findings indicate that the lower mortality from IHD and CVD in Okinawa is affected, at least in part, by Okinawa's warm winter.

Improvement of survival over time for colon cancer patients by anatomical sub-sites.

The aims of this study are to describe and to evaluate improvement of survival over time for colon cancer patients by anatomical sub-sites. Data on 661 patients newly diagnosed as having colon cancer at Osaka Medical Center for Cancer and Cardiovascular Diseases from 1978 to 1991 were examined in this study. Corrected survival was calculated with the Kaplan-Meier method according to the period of diagnosis: early period (1978-84) and later period (1985-91). Factors concerning the difference in survival between the two periods were examined with the Cox proportional hazards regression model according to sub-site. Five-year corrected survival of the patients with left colon cancer improved significantly (60 to 72%; P < 0.01), probably due to advances in treatment, while that of patients with transverse colon cancer also improved significantly (39 to 67%; P < 0.01), mainly because of progress in diagnosis. The five-year corrected survival of those with right colon cancer did not increase (57 to 46%; P = 0.14), owing to lack of improvement in stage at diagnosis. Among the three sub-sites, the right showed the worst five-year survival in the later period. We concluded that survival of patients with right colon cancer, differing from the other anatomical sub-sites, did not improve, possibly because of lack of symptoms. The screening programs for colon cancer introduced in Japan in 1992 may be expected to improve the survival of patients with colon cancer, including that of the right colon.