Epidemiology and Health

Volume 18 (1); June 1996

Original Articles

A Study on Misclassification Arising from Random Error in Exposure Measurement.: Il Suh, Chung Mo Nam, Hyung Gon Kang; Korean J Epidemiol. 1996;18(1):108-118.

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There are many epidemiologic studies to find the relationship between disease occurrence and categorized exposure variables which are measured in continuous scales. Recently, it has been found that the differential misclassification can arise when exposure variables are observed with measurement errors and categorized for the analysis. Even though the differential misclassification leads to serious misclassification bias, there is no theoretical attempt to correct the misclassification bias occuring in these circumstances. In this paper, we propose a new statistical method to reduce the misclassification bias due to dichotomizing continuous exposure variables. Since the exposure values are more likely to be misclassified when the true exposure values are close to the cutoff point, the method proposed here gives smaller weights in these case and more weights when these values are far from cutoff point. Simulation studies are performed to compare the bias and the power of the proposed method compared to other methods. Main results are as follows: 1. The proposed method produces the smaller bias and the higher power than the simple method which modifies misclassified data using sensitivity and specificity of exposure misclassification. 2. When the standard deviation of the measurement error are moderately large, the bias and the power of the proposed estimate are somewhat better than those of the modified estimate which excluding the misclassified observations in the analysis. In conclusion, the method proposed here is found to be useful in epidemiologic studies when continuous exposure variables are obtained with measurement error and categorized in the analysis.; Summary

Usefulness of Somatotype Drawing as a Instrument of Measuring Obesity Level in Korea.: Jong Myon Bae, Yoon Ok Ahn; Korean J Epidemiol. 1996;18(1):101-107.

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BACKGROUND
As modern epidemiologic studies began to identify obesity as a risk factor for cardiovascular disease, diabetes, hypertension, and cancer, measuring the degree of excess body fat is important on epidemiologic surveys. The evaluation of obesity level in epidemiologic surveys has been mostly done indirectly by measuring patient's height and weight. But, the anthropometry could not be done to respondents of recalling past anthropometric values or to proxy respondents. This study was attempted to elucidate usefulness of a somatotype drawing as a measuring instrument of obesity level in epidemiologic surveys in Korea.
METHOD
The inclusion criteria of subjects were (1) members of the Seoul Cohort Study, who were recruited by self-administered structured questionnaire survey through mailing to the healthy men between the ages of 40 and 59 years through the program of a biennial health checkup offered by the Korean Medical Insurance Corporation (KMIC), and (2) volunteers for cancer screening program offered by KMIC. For assessing usefulness of the instrument, measurement of status/weight and self-administered questionnaire survey were done separately through the program of a biennial health checkup and of cancer screening.
RESULTS
The data were collected from 138 subjects, whose Body Mass Index (kg/M2) was 23.58+/-1.46 (mean+/-SD). When the validity was measured through correlation with BMI, Spearman's correlation coefficient (rs) was 0.72 (p<0.05), that remained statistically significant after adjusting age, education level, and monthly income and occupation. And, the grades of somatotypo drawing were grouped as 1-3, 4-6, 7-8 by ANOVA and Tukey test.
CONCLUSIONS
Instrument using somatotype drawing is applicable to screen degree of body fat in self-administered questionnaire surveys in Korea.; Summary

Effects of examination stress on health practices.: Choong Won Lee; Korean J Epidemiol. 1996;18(1):95-100.

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The present study studied the effects of examination stress on the health practices in 69 male medical students prospectively over 3 month period. Average age of the subjects was 23.4 years(range, 21 27). The questionnaires asking the health practices of the previous week were administered on three occasions, during the one week after the one-week midterm examination and examination-free periods of one month before and after examination. Increases in academic demands result in changes of health practices which were statistically significant increased consumption of smoking and mixed drinks and frequency of missed breakfast, and decreases in alcoholic beverage consumption, hours of sleeping and exercise as well as consumption of vegetables, principal foods and oils. These result support the hypotheses that examination stress may exert negative effects on the health practices.; Summary

The relationship of life style and physical health status.: Byung Mann Cho; Korean J Epidemiol. 1996;18(1):84-94.

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The relationship of life style and physical health status was examined in a population of 1656 public servants and teachers(1069 men, 587 women) who had a periodic health examination in 1994. The study items of life style were health-related habits including sleeping time, breakfast snacking, regular exercise, alcohol drinking, cigarette smoking and weight status. Physical health status was evaluated by means of tests including systolic and diastolic blood pressure, hemoglobin, fasting blood glucose, serum total cholesterol, serum GOT and serum GPT. The association between life style and age-adjusted physical health status was examined by ridit analysis. Physical health status was better in women and the younger. The life style significantly associated with age-adjusted physical health status were sleeping time, snacking, regular exercise, weight status and alcohol drinking in men, and breakfast, snacking and weight status in women. The higher score of health practices index, the better age-adjusted physical health status in both sexes. These findings suggest the need for further studies including follow-up study, intervention study on the relationship of life style and health status.; Summary

Impact of the Discontinuance of Regular Exercise on Serum Lipids.: Byung Yeol Chun, Min Hae Yeh, Young Ae Ha; Korean J Epidemiol. 1996;18(1):76-83.

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To estimate the impact the discontinuance of regular exercise on serum lipids, we selected 90 healthy young adults who were recruited and completed their training course as scheduled(5-week basic physical training and 4-week indoor education) during the period February 1995 to April 1995. Serum lipids, height, and weight were measured three times(Time I: before training, Time II: after 5-week training, Time III: after 4-week detraining). Ninety study subjects were classified as underweight, normal and overweight based on the criteria of Katsura equation. Of 17 underweight subjects, two were weight maintainers and 15 were weight gainers. There was no significant change in serum lipids after detraining among 15 weight gainers. Of 64 normal weight subjects, three were weight losers, 12 weight maintainers and 49 were weight gainers. There was significant increase in total cholesterol after detraining among 12 weight maintainers(P<0.01). In addition to this, there was also significant increase in total cholesterol(P<0. 01), LDL- cholesterol(P<0. 01) and HDL-cholesterol(P<0.05) after detraining among 49 weight gainers. This might be due to the harmful effect of detraining except HDL-cholesterol change. Of nine overweight subjects, only one was weight loser and eight were weight maintainers. There was significant increase in HDL-cholesterol after detraining among 7 weight maintainers (P<0.05). However, there were no significant changes in total cholesterol, triglyceride, LDL-cholesterol and MI index. The harmful effect of detraining was not observed in overweight subjects. In conclusion, the harmful effect of detraining was observed in weight maintainers and weight gainers among normal weight subjects after regular exercise.; Summary

Evaluation Studies

An Evaluation Study on the Cardiovascular Risk Factors of the Staff in a University.: Ki Soon Kim, Chan Guk Park, Soon Pyo Hong, Yang Ok Kim, Jong Park, So Yeong Ryu; Korean J Epidemiol. 1996;18(1):64-75.

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To get basic data for the development of health care toward the staff of a university, an evaluation study of the risk factors for the cardiovascular disease utilizing data from questionnaire and health examination performed in 1994 for 1233 staff of Chosun University and its affiliated Hospital. The results are as follows: 1. The mean values of systolic blood pressure was 122.0+/-14.7mmHg for the male and 111.8+/-12. lmmHg for the female. The mean values of diastolic blood pressure was 82. 5+/-12.0mmHg for the male and 73.7+/-10.0mmHg for the female. The mean values of serum total cholesterol was 185.6+/-33.4mg/dl for the male and 173.5+/-32.6mg/dl for the female. The mean values of body mass index(BMI) was 23. l+/-2.4kg/m2 for the male and 21.5+/-2.3kg/m2 for the female. The smoking rate of the male was 47. 6% and that of the female was 0.4%. 2. The systolic and diastolic blood pressure levels increased with age in both sexes. Under 55 years of age the mean blood pressures of the male were higher than that of the female, but the levels of both sexes at 55-64 year old group did not show any big difference. The mean values of serum total cholesterol and BMI also increased with age in both sexes. Under 45 years of age, the serum cholesterol and BMI levels of the male were higher than that of the female, but on the contrary, levels of the male were lower than that of the female at 55-64 year old groups. The mean cholestrol and BMI levels of both sexes at 45-54 year old group was similar. As the age increases, the rate of exsmoker increased and the rate of current smoker decreased among the male. 3. The additive cardiovascular risk scores were calculated considering the values of blood pressure, serum total cholesterol level and the smoking status. The distribution curve of risk scores for the male showed 39. 1% under 4 points and 60.9% above 4 points with the peak at 4 points. 61.7% of the female showed that the risk scores were under 4 points and the rest was more than 4 points with maximum 9 points. As a whole the risk scores of the female were lower than that of the male. 4. By the analysis of association between the risk score of cardiovascular disease and the subjective symptom under the stratification of age and sex, the prevalence of exertional dyspnea was significantly higher at 35-44 year male group and prevalence of dizziness was significantly higher at 45-64 year male group as the risk score of cardiovascular disease increased. Among 25 34 year and 45-64 year female group persons with lower risk score of cardiovascular disease showed higher prevalence of dizziness than persosns with higher risk score.; Summary

Original Article

Prevalence and Epidemiologic Characteristics of Hypertension in a Rural Adult Population.: Joung Soon Kim, Un Yeong Ko, Yong Moon, Min Kyung Lim, Min Joung Ko; Korean J Epidemiol. 1996;18(1):55-63.

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To determine the prevalence and risk factors of hypertension we performed cross-sectional study in a rural area. We measured BP and body mass index(BMI), and interviewed adult residents over 30-year-old age. 337 males and 357 females participated the survey. BP was checked twice and the mean was used to determine age and sex specific mean BP and prevalence of hypertension. Prevalence of definite hypertension(BP>or=160/95 or on medication) was 14. 0% in males and 17. 7% in females. Risk factor for hypertension was analysed by multiple logistic regression; age (10years: OR=l. 7) and BMI(1 BMI unit: OR=l. 2) were positively associated with hypertension but smoking(1 pack year: OR=0.9) was shown to have inverse relationship.; Summary

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