This article is the summary of my Special Lecture at the 14th Annual Scientific Meeting of the Japan Epidemiological Association in 2004. Epidemiology is defined as the “science of investigating the distribution of diseases in human populations and their determinants.” Recent advances in study methodology, especially a widespread conduct of randomized controlled trials (RCTs), have strengthened the scientific basis of epidemiology. When a highly scientific method of investigation is applied to humans, the ethical aspects of the study also become an issue. However, it would also be unethical to use new drugs and vaccines without scientific evidence. The ethical aspects and the scientific aspects of epidemiologic research are thus both very important, but conflict with each other, often causing dilemmas. I would discuss how we could solve these dilemmas and thus contribute ourselves to health promotion and disease prevention of human populations. Finally, I would propose the new paradigm of changing epidemiology into a “neotype science” and transformation of EKIGAKU (epidemiology) into EKIGAKU (beneficial science).
Hypertension has been acknowledged as one of the greatest and established risk factors for cardiovascular diseases. In this special article, strategies for the prevention and management of hypertension throughout human's life were discussed. Studies showing the relationship of birth weight and height increase in childhood to future blood pressure suggest that both environments during pregnancy and during childhood and adolescence are important to prevent hypertension. The promotion of a DASH (Dietary Approach to Stop Hypertension) dietary pattern, rich in fruits and vegetables, is important not only for treatment of high blood pressure but also for long-term prevention of blood pressure rise as well. Blood pressure measured in young adulthood can effectively predict long-term risks of cardiovascular and all-cause mortality, so population-wide primary prevention of high blood pressure for young adults is important. Recent large scale cohort studies confirmed that detection and evaluation of hypertension based mainly on systolic blood pressure remains the most practical and easy approach in the general population for young adult, middle-aged, and older men and women. Researchers in Asia are desired to establish high-quality epidemiologic evidences for Asian for the prevention and management of hypertension.
BACKGROUND: Epidemiologic studies of electromagnetic fields and childhood cancers have focused on home exposure. The authors investigated whether residence in districts near high-voltage power lines is associated with childhood hematological malignancies, using small area analysis. METHODS: Among 50,000 children in a city in Japan, 14 cases aged younger than 15 years were diagnosed with these malignancies in the period from 1992 through 2001. A total of 294 districts constituting this city were classified according to their proximity to high-voltage power lines (either 66 kV or 220 kV). Mantel-Haenszel rate ratio is used to calculate incidence rate ratio and its 95% confidence interval (CI). RESULTS: Compared to districts of which no area fell within 300 m of high-voltage power lines, districts in which at least 50% of the area fell within 300 m of high-voltage power lines demonstrated an increased risk (incidence rate ratio: 2.2; 95% CI: 0.5-9.0). The association was strengthened for homes in which patients had resided for the longest interval of their lives (incidence rate ratio: 3.4; 95% CI: 0.9-13.2). Point-in-time measurements showed no increase in magnetic field levels for patient homes in districts near the lines. CONCLUSION: An increased, albeit nonsignificant, risk of childhood hematological malignancies associated with residential proximity to high-voltage power lines warrants further investigations.
BACKGROUND: Although sleep is one of the most important health-related factors, relationship between sleep duration and mortality has not been fully discussed. METHODS: Study subjects were 11,325 participants (4,419 males and 6,906 females) in the Jichi Medical School Cohort Study, a population-based prospective study. Baseline data were obtained by questionnaire and health checkups between April 1992 and July 1995 in 12 rural areas in Japan. Main outcome measures were all-cause and cause-specific mortality derived from death certificates up to December 31, 2001. Cox's proportional hazard models were applied to analyze the association of sleep duration with mortality. RESULTS: A total of 495 deaths (289 males and 206 females) were observed during the average of 8.2-year follow-up period. After adjusting for age, systolic blood pressure, serum total cholesterol, body mass index, smoking habits, alcohol drinking habits, education, and marital status, the hazard ratios (95% confidence intervals) of all-cause mortality for individuals sleeping shorter than 6 hours and 9 hours or longer were 2.4 (1.3-4.2) and 1.1 (0.8-1.6) in males, and 0.7 (0.2-2.3) and 1.5 (1.0-2.4) in females, respectively, relative to those with 7-7.9 hours sleep. CONCLUSION: Our data suggest that males with short sleep and females with long sleep were at an elevated risk of death.
BACKGROUND: Some case-control association studies revealed the relationship between some endothelin-1 (ET-1) gene polymorphisms and blood pressure. Because no report was available about the relationship between any ET-1 gene polymorphism and incidence of hypertension, we examined the relationship between novel ET-1 gene polymorphism (G862T / Ala288Ser in exon 5) and incidence of hypertension by a retrospective cohort study. METHODS: The subjects were Japanese workers at a company in Shimane Prefecture in Japan. The polymorphism with genome DNA extracted from the blood of the workers was analyzed using the polymerase chain reaction confronting two pair primers method. According to the results of two regular health checkups with a 6-year interval, the study population was divided into two groups by blood pressure and antihypertensive treatment in 1998, after excluding people who had hypertension in 1992. RESULTS: There were 133 (93 males and 40 females) incidences of hypertension observed among the study population of 922 (540 males and 382 females). In the univariate analysis, odds ratios of Ala/Ser and Ser/Ser against Ala/Ala were 0.98 (95% confidence interval [CI]): 0.7-1.4) and 0.79 (95% CI: 0.4-1.6), respectively. In the multivariate analysis adjusted for sex, age, body mass index, serum total cholesterol, fasting blood sugar, and smoking and drinking habits, odds ratios for Ala/Ser and Ser/Ser against Ala/Ala were 0.97 (95% CI: 0.7-1.4) and 0.75 (95% CI: 0.4-1.5), respectively. CONCLUSIONS: The ET-1 gene polymorphism in this study did not seem to be associated with the incidence of hypertension among the Japanese workers.