Ecologic studies are widely used in all fields of public health on account of accesibility of data. However, two problems related to these studies have been brought up. The first is ecological fallacy occurred in the course of interpreting the ecologic level of exposure-disease associations into individual level. The second is exposure isclassification which leads to serious bias. Nevertheless there is few methodologic study dealing joint effects of the two problems in ecologic study. This study was conducted to suggest an ecologic model not having an ecologic fallacy due to model linkage failure and a methodology for correcting the misclassification bias due to exposure-confounder misclassification. Finally, we suggest a criteria for the ecologic model selection. Main results are as follows: 1. A linear ecologic regression model has a serious ecological fallacy due to model linkage failure and the misclassification bias due to the exposure-confounder misclassification. 2. An interaction ecologic regression model has no ecological fallacy due to model linkage failure, but it is affected seriously by the exposure misclassification. However misclassification bias could be removed mathematically if the information related to the misclassification was known. 3. A log-linear ecologic regression model has an ecological fallacy due to model linkage failure. It is seriously biased as the individual risk ratio are increased, but relatively less affected by the exposure misclassification than interaction ecologic regression model. 4. One of the two ecologic regression model-interaction ecologic regression model and log-linear ecologic regression model- would be selected according to the information of individual risk ratio and exposure misclassification. But using a linear ecologic regression model should be avoided in any circumstance. The above results are only valid in case that there is no other source of ecological fallacy except model linkage failure. Also exposure and confounder are independent each other, measured binary, and having nondifferential misclassification. Since the above assumptions are somewhat strong in considering the real situations of ecologic studies, it is necessary to extend the scope of this study.
Bias (Epidemiology) ; Joints ; Odds Ratio ; Public Health

No abstract available.
Animals ; Calcitonin* ; Female ; Osteoporosis* ; Ovariectomy* ; Rats* ; Tamoxifen*

The purpose of this study was to investigate the incidence rate of hepatitis B in the military service and to examine the effect of the asymptomatic HBsAg carriers on the incidence of hepatitis B. The subject were 223,270 men who were conscripted to the Korean Army from 1991 to 1994 year. According to the conscripted year, four conscription cohort were constructed. At the screening examination for military service no test for hepatitis B were performed in 1991 and 1992. In 1993, a screening test for hepatitis B were performed and those who were confirmed as HBsAg positive or > or = SGPT 100IU were excluded from conscription. In 1994, the criteria for conscription was changed and those who were HBsAg positive were not excluded from conscription. Only those who were > or =SGPT 100IU were excluded. The main results were as follows ; 1. The positive rate of HBsAg is 5.5% in the conscripted men. 2. The incidence rates of the hepatitis B in 1991 and 1992 conscription cohort were 9.96 and 8.10 per ten thousand per son - year, respectively. The incidence rate of the hepatitis B was 1.34 per ten thousand per son - year in 1993 conscription cohort which was confirmed as HBsAg negative at the screening test, and 7.41 per ten thousand per son - year in 1994 conscription cohort which included the HBsAg positive. 3. The incidence rate of hepatitis B was 99.98 per ten thousand per son- year in HBsAg positive group and 2.25 per ten thousand per son - year in HBsAg negative group. The incidence rate of the group with high SGPT and HBsAg positive was 255 times higher than that of normal population. 4. The incidence of hepatitis B in HBsAg negative group did not increase even though the probability of personal contact with HBsAg positive had been increased. From the above result s, the men who have high SGPT with HBsAg positive should be excluded from military service, and it can not be said that asymptomatic HBsAg carrier s influence on the hepatitis B incidence among the HBsAg negative through personal contact.
Alanine Transaminase ; Cohort Studies ; Hepatitis B Surface Antigens* ; Hepatitis B* ; Hepatitis* ; Humans ; Incidence* ; Male ; Mass Screening ; Military Personnel*