The northern district of R Town, Yamagata Prefecture, Japan, experienced an epidemic of acute hepatitis C during the 6 years following 1967. A mass survey health examination for hepatitis C virus (HCV) infection was performed on the inhabitants of this district aged 6 or over (4, 655 people). Of the 3, 094 inhabitants (66.5%) examined, 602 (19.5%) were anti-HCV antibody (anti-HCV) positive. Of the 602 anti-HCV positive subjects, 444 (73.7%) showed an anti-HCV cutoff index of over 4.0 (high titer), 54 (9.0%) showed 3.0-4.0 (middle titer), and 104 (17.3%) showed an index of under 3 (low titer). One hundred and sixty subjects, randomly selected, were examined for HCV RNA by nested polymerase chain reaction, and positive reactions were detected in 125 subjects (78.1 %). The anti-HCV positive rate differed greatly between subjects younger than 40 years (18/1, 289 ; 1.4%) and those 40 or over (584/1, 805 ; 32.4%). Those who had lived in this district since before the acute hepatitis C epidemic had a high rate of positive anti-HCV. Among the 47 hamlets in this farming district, the hamlet with the highest rate (71.4%) was surrounded by other hamlets where the rates decreased as the distance from the high rate hamlet increased. The study suggested a marked regional accumulation of HCV infection in this district and an age-related difference in HCV infection rates. The cause of the accumulation was not identified, although the HCV infection in this district may have been spread during or before the acute hepatitis C epidemic and produced many HCV carriers. J Epidemiol, 1996 ; 6 : 1-7.
To evaluate the validity of the recall method in estimating food intake in the distant past, we assessed past and current food intakes by mailed food questionnaires among 80 residents in Gifu, Japan who had answered the same questionnaire 9 years ago. We compared rank correlations and differences between recalled food intake scores and past ones with those between current food intake scores and past ones. We observed higher scores of recalled intake for meat, potatoes and alcohol, and a lower score of recalled intake for cereals than the scores of past intake. We observed increase in food intake scores of soybean products, dairy products and potatoes and decrease in that of cereals intakes from past to current. The rank correlation coefficients between the recalled and past food intake scores (r=0.24-0.89) were greater than those between the current and past ones (r=0.10-0.70) for every food item except for dairy products. After stratification by sex, age and degree of change in body mass index (BMI), the greater correlation between the recalled and past food intake scores remained. These findings suggest that the recall method is more preferable than the current data to estimate food intake in the distant past in Japan. J Epidemiol, 1996 ; 6 : 9-13.
A 15.5-year follow-up study of ischemic heart disease among residents 40 years and older in a rural community, A-I district, Shibata City, Niigata Prefecture, Japan, was completed in 1992. The response rate for the initial examination was 84.5% of 1, 182 men and 92.6% of 1, 469 women. Nine hundred and eighty-five men and 1, 344 women who were initially free of ischemic heart disease were followed from July 1977 through December 1992. The person-year incidence of possible myocardial infarction (PMI) was 1.01 per 1, 000 for men and 0.59 for women, and that of sudden death within 24 hours (24SD) was 1.08 for men and 0.64 for women. In the sex-, and age-stratified univariate analyses by the Cox proportional hazard regression model, statistically significant relative risk of PMI was observed for systolic (SBP), diastolic (DBP) and mean blood pressure (MBP), body mass index and smoking. For 24SD, DBP and albuminuria were selected as significant risk factors. In the multivariate analyses, MBP and smoking were selected as independent risk factors for PMI. No significant association of any factor with 24SD was detected. The influence of serum cholesterol on occurrence of PMI appeared to be subtle. J Epidemiol, 1996 ; 6 : 15-22.
The reliability of a questionnaire which contained 21 items concerning asthma and allergies of the nose, skin, and eyes and other questions was evaluated by test-retest method. The questionnaire was the same as one used two years ago in a survey of allergic diseases found among elementary, junior and senior high school students in Shizuoka Prefecture, Japan. In order to evaluate its reliability, calculations were made of proportions of agreement, Cohen’s kappa values and intraclass correlation coefficients. Both the proportions of agreement and the kappa values were fair, and all the intraclass correlation coefficients showed high values. The results suggest that there might be a slight effect of age, and that the articles which showed higher kappa values tended to be easy to answer, while the items in which kappa values were lower tended to consist of questions of multiple answers. This questionnaire can be regarded as useful for our original purpose of investigating allergic diseases. Among the kappa values of items, the values regarding diagnosis by doctor tended to be the largest. It was suggested that doctor’s diagnosis was strongly convincing for patients. The reliability of this questionnaire survey can be regarded as satisfactory. J Epidemiol, 1996 ; 6 : 23-30.
Maximal oxygen consumption (VO2 max) is the criterion measure of cardiorespiratory fitness. However, because it has traditionally been regarded as a costly, labor-intense measure to obtain, VO2 max assessment has seen only limited use in epidemiological studies. Recently, methods for predicting V02 max have been developed that rely on a combination of self-report variables. The purpose of this study was to determine the relationship of two multivariable equations for estimating V02 max in a sample of 123 females (M age=38.8+8.4 yrs.). In one equation a sevenitem physical activity index was used and in the other equation a single physical activity question was used. The between-formula relationship for predicted V02 max values was significant (r=0.80, p<0.0001). Predicted V02 max values were also positively related with other indices of physical activity (rs=0.26 to 0.74). Preliminary results suggest there is a high degree of correlation between the two equations studied, as well as other indices of physical activity. These formulas may be of interest to epidemiologists in situations where direct methods of V02 max assessment are not feasible. J Epidemiol, 1996; 6 : 31-35.
A cooperative hospital-based case-control study of idiopathic avascular necrosis of the femoral head (IANF) was carried out to clarify the involvement of smoking, drinking, flushing pattern, and other factors in the development of IANF comparing 90 cases (64 males and 26 females) without history of systemic corticosteroid use with 180 matched controls (128 males and 52 females). The results of analyses were represented only for male subjects because of small number of female cases. There was no significant difference in smoking habits, daily and cumulative number of cigarettes smoked between case and control groups. Current drinkers had obviously higher risk (OR=11.47) of IANF compared to nondrinkers or exdrinkers. In addition, there was a consistent risk increase with increasing alcohol consumption and the highly significant dose-response relationship remained unchanged after adjustment for all other factors (X2=14.33, p<0.001 and X2=13.24, p<0.001 for daily and cumulative alcohol consumption, respectively). For flushing pattern, although nonflushers had a significantly elevated risk (OR=2.08) in the univariate analysis, the association disappeared (OR=0.73) after adjustment for alcohol and other factors. Since nonflushers tend to be heavy drinkers, perhaps, an apparent risk increase among nonflushers may be due to alcohol drinking. Body mass index (BMI) was inversely related to the development of IANF. The risk reduction was found among subjects with higher BMI and an adjusted linear trend of OR was significant (X2=6.65, p<0.05). However, further studies were required regarding the association between flushing pattern or BMI and IANF because of a few reports. History of liver diseases and occupational history were not significantly associated with the development of IANF after adjustment for other factors. J Epidemiol, 1996; 6:37-43.
A self-administered food frequency questionnaire (FFQ) has been used commonly in epidemiologic studies of diet and chronic diseases. The analysis of dietary data in the target population is useful for designing a new questionnaire. The authors studied the major food sources of nutrient intakes in the Japanese population in order to develop a FFQ for a population-based prospective study. Subjects were 180 men aged 40-49 years and their 155 spouses who were sampled from four Public Health Center districts. Weighed food records over three consecutive weekdays were collected during the winters of 1989-1991. All foods reported were grouped into 154 items, and the percent contribution of each food to the total population intake of 15 nutrients was computed. Based on these data, a FFQ with 138 items was developed. The food list covered well the population intake of most nutrients (median=83%, range=55-91 %), except for lipid (70%) and sodium (55%). The questionnaire was applied to the prospective study conducted in the same areas where the dietary data were collected, and an investigation to assess its reproducibility and validity is currently underway. J Epidemiol, 1996; 6 : 45-53.
Interest in the health hazards of weight loss and regain (weight cycling) is growing. This study examined the relationship between weight cycling during ages 21 to 35 and changes in coronary risk factors (systolic blood pressure, diastolic blood pressure, total cholesterol, and HDL cholesterol) during ages 35 to 40. We followed up 264 blue-collar workers from the time they were 21 to 40 years of age working for one company. Analysis of covariance was applied including the number of weight cycles during ages 21 to 35 as the independent variable and the changes in coronary risk factors between age 35 and 40 as the dependent variables. The covariates were adjusted for body mass index (BMI) at age 35, increase in BMI between ages 35 and 40, value of coronary disease risk factors at age 35, and smoking status at age 40. The results showed that increase in systolic and diastolic blood pressure was not significantly related to the number of weight cycles. For total and HDL cholesterol, interaction was seen between smoking status and the number of weight cycles, and the effects of weight cycle on cholesterol levels were examined by smoking status. The change in total cholesterol among frequent cyclers was not significantly different from that among non-cyclers. Though the increment of HDL cholesterol in frequent cyclers was significantly larger than that in non-cyclers for non-smokers, an inverse relationship was seen for heavy smokers (not significant). Our results showed the effects of weight cycling on changes in coronary risk factors only for HDL cholesterol based on analysis by smoking status. As the present study was conducted on a small population, interaction between weight cycling and smoking status on HDL cholesterol should be confirmed using a larger population. J Epidemiol, 1996 ; 6 : 55-62.