This study presents a comparative risk pattern for cancer of the oral cavity, pharynx and larynx, in relation to cigarette smoking and alcohol consumption based on data from case-control studies conducted in Korea Cancer Center Hospital, Seoul, Korea. The risk of cancer of the oral cavity, pharynx and larynx rose for current smokers and declined for ex-smokers. In males the odds ratios (ORs) for these sites rose with duration of smoking and number of cigarettes smoked per day. The relationship is strongest for laryngeal cancer. The risk for all sites was elevated linearly as amount and frequency of alcohol intake increased. Heavy drinkers, i.e. males who drank 90 g ethanol daily had an approximately 15-fold risk of cancer of the oral cavity, an 11-fold risk of pharyngeal cancer and an 11-fold risk of laryngeal cancer compared with non-drinkers. Alcohol drinking was a much stronger risk factor for cancer of the oral cavity than cancer of the pharynx and larynx. Alcohol was a much weaker risk factor for laryngeal cancer than cigarette smoking. Cancer of the oral cavity, pharynx and larynx also showed an interaction between smoking and alcohol, suggesting a synergistic effect.

Seasonal variations in the proportion of preterm births in Japan from January 1979 to December 1983 are analysed using a traditional method of time-series analysis, which divides the variation in a series into trend, seasonal variation, other cyclic change, and remaining irregular fluctuations. It is shown that the proportion of preterm births in Japan have a clear seasonal periodicity with two peaks in summer and winter. Analysis of seasonality by period of gestation shows that interesting differences in kurtosis and skewness exist between summer and winter, i.e. the summer increase in preterm births was characterized by an increase of skewness which means an extension of the lower part of the distribution. On the other hand, the winter increase was characterized by a decrease of kurtosis which corresponds to a flat-topped distribution. This result suggests that causes of preterm births might be different between the two seasons. Theoretical simulations based on actual birth data in Japan over the period, are carried out to examine how season of conception could influence seasonal variations in the proportion of preterm births. Results show that, at least for first births, seasonality in conception rates could be one explanatory factor for the observed seasonal variation in proportions of preterm births. Another analysis reveals that conception in May and June are more likely to result in preterm births in Japan.

Seasonal variations of births in six different prefectures in Japan are analysed using Vital Statistics from 1974 to 1983. First births show a bimodal pattern with two peaks, one in winter (December-February) and the other in summer to early autumn (August-September). The seasonality of first births is statistically significantly correlated with the seasonality of marriages with 9 + 12*n (n = 0, 1, 2, 3) lag months. For subsequent births, the seasonal pattern is unimodal and there is also a geographical trend in seasonality of these births with a late spring peak in the northernmost prefecture of Japan giving way to an early autumn peak in the southernmost prefecture. These findings suggest that seasonal variations in marriage play some role in the seasonality of first births, while other features such as environmental factors could be associated with the seasonal variations of subsequent births. Changes in the seasonality of both births and marriages over time suggest that the modernization of Japanese society after the second World War could be responsible for the drastic changes in the pattern and degree of seasonality of births.

This study presents the comparative patterns of risk of selected digestive tract cancers (esophagus, stomach, colon, rectum and liver) for males in relation to cigarette smoking and alcohol drinking, based on the data from case-control studies conducted in the Korea Cancer Center Hospital (KCCH). There was strong positive association between cigarette smoking and esophageal cancer, but none of the other sites was significantly related to cigarette smoking. In esophageal cancer, a dose-dependent effect for cigarette smoking was observed, with the odds ratio ranging from 1.29 for ever smoking up to 1 pack daily to 3.17 for smokers of more than 2 packs per day. The risk declined markedly following cessation of smoking. Cancers of the esophagus, rectum and liver were strongly related to alcohol consumption. Compared with non-drinkers, the OR for heavy drinkers was 9.14 in esophageal cancer, 4.75 in rectal cancer and 2.46 in liver cancer. In cancer of the stomach and colon, however, there was no association with alcohol drinking.

No abstract