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Objectives: The objective of this study was to calculate sample size and power in an ongoing cohort, Korea radiation effect and epidemiology cohort (KREEC)., Method: Sample size calculation was performed using PASS 2002 based on Cox regression and Poisson regression models. Person-year was calculated by using data from '1993-1997 Total cancer incidence by sex and age, Seoul' and Korean statistical informative service., Results: With the assumption of relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, sample size calculation was 405 events based on a Cox regression model. When the relative risk was assumed to be 1.5 then number of events was 170. Based on a Poisson regression model, relative risk=1.3, exposure:non-exposure=1:2 and power=0.8 rendered 385 events. Relative risk of 1.5 resulted in a total of 157 events. We calculated person-years (PY) with event numbers and cancer incidence rate in the non-exposure group. Based on a Cox regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, 136 245PY was needed to secure the power. In a Poisson regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, person-year needed was 129517PY. A total of 1939 cases were identified in KREEC until December 2007., Conclusions: A retrospective power calculation in an ongoing study might be biased by the data. Prospective power calculation should be carried out based on various assumptions prior to the study.

Objectives: Our objective was to examine and evaluate the psychological health of the residents of Taean during the cleanup of the Hebei Spirit (HS) oil spill and to review some factors associated with the results., Methods: A community survey of 71 men and women was conducted 8 weeks after the HS oil spill. Questionnaires used were the PWI (Psychological Well-being Index) scale for psychosocial distress, the CES-D (Center for Epidemiologic Studies-Depression) scale for depressive symptoms, and a questionnaire created to assess suicidal impulses., Results: The overall prevalence of high-risk psychosocial distress among the study group was 64.2%. The percentages of respondents with scores on the CES-D Scale above 16 and above 21 were 77.6% and 62.7%, respectively. The percentage of respondents categorized as having suicidal impulses was 18.3%. When compared with unexposed groups in the general population taken from various sources, the residents of Taean were 6.5 times as likely to have high stress and 9.4-9.7 times as likely to be depressed. No significant difference in the rate of suicidal impulse was found between the residents of Taean and the general population. Factors associated with high stress, depression, and suicidal impulses were age, a change in income, educational level, number of days working on the cleanup, and positive responses to questions about "affected daily activity" and "hospital visit due to work on cleanup.", Conclusions: The results suggest that the HS oil spill had a significant impact on the psychological health of residents of Taean, but the comparability of the unexposed groups is a limitation of the study.