- Cohort Study for the Effect of Chronic Noise Exposure on Blood Pressure among Male Workers.
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Ji Ho Lee, Tae Joon Cha, Jang Rak Kim, Weechang Kang, Seung Rim Yaang, Choong Ryeol Lee, Cheol In Yoo
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Korean J Prev Med. 2002;35(3):205-213.
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Whether exposure to chronic noise induces an increase in blood pressure, or the development of hypertension, has not been established. A cohort study was performed to identify the effects of chronic noise exposure on blood pressure. METHODS: 530 males working at a metal manufacturing factory in Busan, Korea were enrolled for the study. They were monitored for 9 consecutive years, from 1991 to 1999, with an annual health check-up. The subjects were divided into 4 groups, which were determines by noise level categories(NLC) according to noise intensity ; NLC-I: office workers, exposed to noise a level below 60dB(A); NLC-II: field technical supporters or supervisors, frequently exposed to workplace noise, wearing no hearing protection device; NLC-III: workers, exposed to workplace noise below 85 dB(A), wearing ear plugs or muffs; NLC-IV: workers, exposed to workplace noise over 85 dB(A), wearing both ear plugs and muffs. RESULTS: After controlling possible confoundens, such as baseline age, smoking, alcohol intake, exercise, family history of hypertension, systolic(SBP) or diastolic blood pressure(DBP) and changes in BMI (body mass index), the pooled mean for the systolic blood pressures, over the duration of the study period, were 3.8mmHg, 2.0mmHg and 1.7mmHg higher in NLC-IV, NLC-III NLC-II groups, respectively, than in the NLC-I group. There were no significant differences in the diastolic blood pressures between the groups. CONCLUSION: This study suggests that chronic noise exposure increases systolic blood pressure independently, among male workers.
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- An Approach to Survey Data with Nonresponse: Evaluation of KEPEC Data with BMI.
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Jieun Baek, Weechang Kang, Youngjo Lee, Byung Joo Park
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Korean J Prev Med. 2002;35(2):136-140.
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A common problem with analyzing survey data involves incomplete data with either a nonresponse or missing data. The mail questionnaire survey conducted for collecting lifestyle variables on the members of the Korean Elderly Phamacoepidemiologic Cohort(KEPEC) in 1996 contains some nonresponse or missing data. The proper statistical method was applied to evaluate the missing pattern of a specific KEPEC data, which had no missing data in the independent variable and missing data in the response variable, BMI. METHODS: The number of study subjects was 8,689 elderly people. Initially, the BMI and significant variables that influenced the BMI were categorized. After fitting the log-linear model, the probabilities of the people on each category were estimated. The EM algorithm was implemented using a log-linear model to determine the missing mechanism causing the nonresponse. RESULTS: Age, smoking status, and a preference of spicy hot food were chosen as variables that influenced the BMI. As a result of fitting the nonignorable and ignorable nonresponse log-linear model considering these variables, the difference in the deviance in these two models was 0.0034(df=1). CONCLUSION: There is a lot of risk if an inference regarding the variables and large samples is made without considering the pattern of missing data. On the basis of these results, the missing data occurring in the BMI is the ignorable nonresponse. Therefore, when analyzing the BMI in KEPEC data, the inference can be made about the data without considering the missing data.
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- Cost-Effectiveness Analysis of a Hyperlipidemia Mass Screening Program in Korea.
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Yeon Soon Cha, Young Ho Khang, Moo Song Lee, Weechang Kang, Sung Hoon Jeon, Kee Lak Kim, Sang Il Lee
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Korean J Prev Med. 2002;35(2):99-106.
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Until now, there have been no evidence-based guidelines produced for the mass screening of hyperlipidemia cases in Korea. This study was done to find the most efficient strategy for a hyperlipidemia-screening program among Korean adults. METHOD: Seven alternative strategies for hyperlipidemia screening were formulated and compared in terms of cost-effectiveness. Cost and effectiveness were estimated from social perspectives and using a two-stage screening process (initial testing and additional testing for positives from the first test). A computerized database (based on persons who had visited a health promotion center in one teaching hospital for a routine health check-up) was used to determine the cost and the outcome of various strategies. Official data was used in calculating direct and indirect costs. Effectiveness was measured according to the number of persons who needed clinical intervention for hyperlipidemia. A stratified analysis, considering age group and sex, was then done. Sensitivity analyses, focusing on several uncertain parameters, were also done. RESULTS: Of the seven test alternatives available, the most cost-effective strategy was a screening program, which consisted of an initial test of total cholesterol,high-density lipoprotein cholesterol and triglyceride. There was some variation in the rank of the cost-effectiveness ratios for the seven alternatives dependent on age group or gender. CONCLUSIONS: Current hyperlipidemia screening practice, for National Health Insurance beneficiaries, tests only the total cholesterol level with a cut-off value of 260mg/dl as an initial screening test. It is not the best strategy for cost-effectiveness, and should be modified. Different screening strategies taking age group and sex into account should be developed and used for the efficient mass screening of hyperlipidemia cases among Korean adults.
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- Inter-hospital Comparison of Cesarean Section Rates after Risk Adjustment.
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Sang Il Lee, Young Ho Khang, Beom Man Ha, Moo Song Lee, Weechang Kang, Hee Jo Koo, Chang Yup Kim
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Korean J Prev Med. 2001;34(4):337-346.
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To determine the clinical risk factors associated with the mode of delivery decision and to compare cesarean section rates after adjusting for risk factors identified among Korean hospitals. METHODS: Data were collected from 9 general hospitals in two provincial regions by medical record abstraction during February 2000. A total of 3,467 cases were enrolled and analyzed by stepwise logistic regression. Performance of the risk-adjustment model (discrimination and calibration) was evaluated by the C statistic and the Hosmer-Lemeshow test. Crude rates, predicted rates with 95% confidence intervals, and adjusted rates of cesarean section were calculated and compared among the hospitals. RESULTS: The average crude cesarean section rate was 53.2%, ranging from 39.4% to 65.7%. Several risk factors such as maternal age, previous history of cesarean section, placenta previa, placental abruption, malpresentation, amniotic fluid abnormality, gestational anemia, infant body weight, pregnancy-induced hypertension, and chorioamnionitis were found to have statistically significant effects on the mode of delivery. It was confirmed that information about most of these risk factors was able to be collected through the national health insurance claims database in Korea. Performance of the risk-adjustment model was good (c statistic=0.815, Hosmer-Lemeshow test=0.0621). Risk factor adjustment did lead to some change in the rank of hospital cesarean section rates. The crude rates of three hospitals were beyond 95% confidence intervals of the predicted rates. CONCLUSIONS: Considering that cesarean section rates in Korean hospitals are too high, it is apparent that some policy interventions need to be introduced. The concept and methodology of risk adjustment should be used in the process of health policy development to lower the cesarean section rate in Korea.
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- Complementary and Alternative Medicine Use in Korea: Prevalence, Pattern of Use, and Out-of-pocket Expenditures.
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Sang Il Lee, Young Ho Khang, Moo Song Lee, Hee Jo Koo, Weechang Kang, Changgi D Hong
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Korean J Prev Med. 1999;32(4):546-555.
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To determine the prevalence, pattern, and out-of-pocket expenditure of complementary and alternative medicine (CAM) utilization in Korean adult population. METHODS: We conducted a representative telephone survey of 2,042 persons aged 18 or older. Data about any health problem, details of their use of medical doctors(MDs) offices/hospitals/ pharmacies services and CAM during the preceding 12 months were collected with structured questionnaire. RESULTS: The utilization rate of CAM among Korean adults was 29% in one year. A total of 231 kinds of CAM was identified from this survey. Annual out-of-pocket expenditure associated with CAM use in 1998 amounted to pound $1.88 billion and was comparable to 40.8% of out-of-pocket expenditure paid for MDs offices/ hospitals/pharmacies services. Among those(N=424) who paid for both MDs offices/hospitals/pharmacies services and CAM, 35.8% paid more for CAM. CAM gave more satisfaction than western medicine to those who had experience of both types of therapy. About half of CAM users were willing to recommend CAM to others. Disclosure rate to physician among CAM users was not high(40.6%). CONCLUSION: CAM became a popular source of health care in Korea. Korean spent a substantial amount of out-of-pocket money on CAM without any public control. Because CAM use is likely to be increased rapidly through lay referral system, health policy makers and health professionals should pay more attention to CAM for making appropriate utilization of CAM.
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