Background: Although pancreatic cancer has been extensively studied, few risk factors have been identified, and no validated biomarkers or screening tools exist for early detection in asymptomatic individuals. We present a broad overview of molecular epidemiologic studies that have addressed the relationship between pancreatic cancer risk and genetic polymorphisms in several candidate genes and suggest avenues for future research. Methods: A comprehensive literature search was performed using the PubMed database. Results: Overall, individual polymorphisms did not seem to confer great susceptibility to pancreatic cancer; however, interactions of polymorphisms in carcinogen-metabolizing genes, DNA repair genes, and folate-metabolizing genes with smoking, diet, and obesity were shown in some studies. The major problem with these studies is that, due to small sample sizes, they lack sufficient statistical power to explore gene–gene or gene–environment interactions. Another important challenge is that the measurement of environmental influence needs to be improved to better define gene–environment interaction. It is noteworthy that 2 recent genome-wide association studies of pancreatic cancer have reported that variants in ABO blood type and in 3 other chromosomal regions are associated with risk for this cancer, thus providing new insight into pancreatic cancer etiology. Conclusions: As is the case in other complex diseases, common, low-risk variants in different genes may act collectively to confer susceptibility to pancreatic cancer in individuals with repeated environmental exposures, such as smoking and red meat intake. Clarification of gene–gene and gene–environmental interaction is therefore indispensable for future studies. To address these issues, a rigorously designed molecular epidemiologic study with a large sample is desirable.
Background: Each ethnic group has its own cultural values and practices that widen inequalities in child health and survival among ethnic groups. This study seeks to examine the mediatory effects of ethnicity and socioeconomic position on under-5 mortality in Nigeria. Methods: Using multilevel logistic regression analysis of a nationally representative sample drawn from 7620 females age 15 to 49 years in the 2003 Nigeria Demographic and Health Survey, the risk of death in children younger than 5 years (under-5 deaths) was estimated using odds ratios with 95% confidence intervals for 6029 children nested within 2735 mothers who were in turn nested within 365 communities. Results: The prevalence of under-5 death was highest among children of Hausa/Fulani/Kanuri mothers and lowest among children of Yoruba mothers. The risk of under-5 death was significantly lower among children of mothers from the Igbo and other ethnic groups, as compared with children of Hausa/Fulani/Kanuri mothers, after adjustment for individual- and community-level factors. Much of the disparity in under-5 mortality with respect to maternal ethnicity was explained by differences in physician-provided community prenatal care. Conclusions: Ethnic differences in the risk of under-5 death were attributed to differences among ethnic groups in socioeconomic characteristics (maternal education and to differences in the maternal childbearing age and short birth-spacing practices. These findings emphasize the need for community-based initiatives aimed at increasing maternal education and maternal health care services within communities.
Background: Much effort has been expended on interpreting the mechanism of influenza epidemics, so as to better predict them. In addition to the obvious annual cycle of influenza epidemics, longer-term incidence patterns are present. These so-called interepidemic periods have long been a focus of epidemiology. However, there has been less investigation of the interepidemic period of influenza epidemics. In the present study, we used spectral analysis of influenza morbidity records to indentify the interepidemic period of influenza epidemics in Japan. Methods: We used time series data of the monthly incidence of influenza in Japan from January 1948 through December 1998. To evaluate the incidence data, we conducted maximum entropy method (MEM) spectral analysis, which is useful in investigating the periodicities of shorter time series, such as that of the incidence data used in the present study. We also conducted a segment time series analysis and obtained a 3-dimensional spectral array. Results: Based on the results of power spectral density (PSD) obtained from MEM spectral analysis, we identified 3 periodic modes as the interepidemic periods of the incidence data. Segment time series analysis revealed that the amount of amplitude of the interepidemic periods increased during the occurrence of influenza pandemics and decreased when vaccine programs were introduced. Conclusions: The findings suggest that the temporal behavior of the interepidemic periods of influenza epidemics is correlated with the magnitude of cross-reactive immune responses.
Background: Accessible public information on self-reported height and weight is not widely used in studies of obesity, mainly because of the questionable validity of body mass index (BMI) values calculated from these data. To assess the utility of self-reported measurement, we compared self-reported and standard measurements of height and weight in a Korean population that is leaner than Western populations. Methods: A cross-sectional comparison of self-reported and measured height and weight was conducted among a population of participants in a cancer screening program. A total of 557 men and 1010 women aged 30 to 70 years were included in the current analysis. Results: Self-reported height was higher than measured values in both men and women. Self-reported weight was higher than measured weight in women, but was not different in men. BMI calculated from measured values was higher than BMI derived from self-reported height and weight among men. Younger age was a predictor of accuracy in self-reported height, and higher weight and BMI were predictors of under-reporting of weight. The prevalence of obesity based on self-reported values was lower than the true prevalence of obesity. With respect to classifying individuals as obese, the specificity and sensitivity of BMI calculated from self-reported values were very high for both sexes. Conclusions: Self-reported height and weight were reasonably valid in this study population.
Background: Several epidemiological and experimental studies have found a positive association between the risk of motor vehicle accidents (MVAs) and use of zopiclone and benzodiazepines. There is, however, little evidence of any risk of MVA attributable to the use of zolpidem 1 day before such accidents. We attempted to determine whether the use of zolpidem 1 day before is associated with an increased risk of an MVA. Methods: Using a 1-million-person randomly sampled cohort from the Taiwan National Health Insurance reimbursement database, 12 929 subjects were identified as having been hospitalized between 1998 and 2004 due to an MVA. Using a case–crossover design, we selected the day before an MVA as the case period for each subject, and the 91st, 182nd, and 273rd days before the case period as 3 retrospective control periods. Conditional logistical regression models were constructed to calculate the odds ratio (OR) of having an MVA and the exposure of zolpidem 1 day before. We calculated doses of benzodiazepines, zopiclone, and zolpidem based on their defined daily dose. Results: The adjusted OR for involvement in an MVA after taking 1 defined daily dose of zolpidem was 1.74 (95% confidence interval: 1.25–2.43). There were also positive effects for different washout periods and cumulative doses at 7, 14, 21, and 28 days before the occurrence of an MVA. Conclusions: Use of zolpidem 1 day before might be associated with an increased risk of MVA. Thus, precautionary warnings should be provided when prescribing zolpidem.
Background: It has been suggested that participant withdrawal from studies can bias estimates. However, this is only possible when withdrawers and nonwithdrawers differ in an important way. We tested the hypothesis that withdrawers are more likely than nonwithdrawers to be avoidant and negatively affected. Methods: A total of 1160 participants with inflammatory bowel disease were recruited at different sites in Switzerland. Their levels of avoidance coping and negative affectivity were rated by means of 2 short baseline questionnaires. One year later, they were sent a longer follow-up questionnaire. The primary outcome was return versus non-return of the follow-up questionnaire within 3 months. After controlling for potential confounders identified in an extensive literature search, we estimated the odds of returning the follow-up questionnaire for 1 standard deviation of avoidance coping and negative affectivity. Results: The odds ratio for 1 standard deviation was 1.03 (95% confidence interval: 0.89–1.18) for avoidance coping and 1.02 (0.89–1.17) for negative affectivity. Conclusions: The odds of returning the questionnaires did not depend on avoidance coping or negative affectivity.
Background: High-density lipoprotein cholesterol (HDL-C) is reported to be associated with breast cancer risk. To better understand this association, we examined the relationship between HDL-C and mammographic density, a putative intermediate risk factor for breast cancer. Methods: The study subjects were 711 Korean women from the Healthy Twin study. Lipid parameters were assayed enzymatically in fresh sera, and percent dense area (PDA) and absolute dense area were measured from digital mammograms using a computer-assisted method. Results: PDA was positively associated with HDL-C in both premenopausal and postmenopausal women in a multivariable-adjusted linear mixed model, but the association did not persist when the model was additionally adjusted for body mass index (BMI). BMI was inversely associated with PDA, and this association did not change after additional adjustment for any lipid parameter. Multivariable-adjusted analysis showed that there were significant additive genetic cross-trait correlations between PDA and both HDL-C (coefficient, 0.175) and triglyceride (coefficient, −0.262). However, those correlations disappeared after additional adjustment for BMI. Conclusions: HDL-C alone is unlikely to increase the risk of breast cancer in Korean women, particularly through changes in breast parenchyma that are apparent in mammographic density. BMI should be included in studies using analytical models where mammographic density is used as an intermediate risk factor for breast cancer.
Background: The adverse effects of maternal smoking on the health of pregnant women have been examined mostly on a disease-by-disease basis. The aims of this study were to evaluate simultaneously the effects of smoking during pregnancy on various obstetric complications, using data from a large medical database, and to investigate the expediency of using a case-cohort design for such an analysis. Methods: A case-cohort study was conducted within the Japan Perinatal Registry Network database. Perinatal information on infant deliveries was entered into the database at 125 medical centers in Japan. The base population of the study was 180 855 pregnant women registered in the database from 2001 through 2005. The outcome measures were the incidences of 11 different obstetric complications. Logistic regression models were used to estimate age-adjusted risk ratios (aRRs) and relative excess incidence proportions (REIs). Results: The overall prevalence of smoking during pregnancy was 5.8% in the base cohort, and the prevalence was higher among younger women. A comparison of the cases and control cohort showed that smokers during pregnancy had statistically significant higher risks for preterm rupture of the membrane (aRR: 1.67, 95% confidence interval [CI]: 1.43–1.96; REI: 40.2%, 95% CI: 29.9%–49.1%), chorioamnionitis (1.65, 1.36–2.00; 39.4%, 26.4%–50.0%), incompetent cervix (1.63, 1.35–1.96; 38.5%, 25.8%–49.1%), threatened premature delivery (1.38, 1.17–1.64; 27.7%, 14.5%–38.9%), placental abruption (1.37, 1.10–1.72; 27.1%, 8.8%–41.7%), and pregnancy-induced hypertension (1.20, 1.01–1.41; 16.4%, 1.2%–29.3%). Conclusions: Maternal smoking was associated with a number of obstetric complications. This highlights the importance of smoking cessation during pregnancy. In addition, case-cohort analysis proved useful in estimating RRs for multiple outcomes in a large database.
Background: We investigated the relationship between low cholesterol and mortality and examined whether that relationship differs with respect to cause of death. Methods: A community-based prospective cohort study was conducted in 12 rural areas in Japan. The study subjects were 12 334 healthy adults aged 40 to 69 years who underwent a mass screening examination. Serum total cholesterol was measured by an enzymatic method. The outcome was total mortality, by sex and cause of death. Information regarding cause of death was obtained from death certificates, and the average follow-up period was 11.9 years. Results: As compared with a moderate cholesterol level (4.14–5.17 mmol/L), the age-adjusted hazard ratio (HR) of low cholesterol (<4.14 mmol/L) for mortality was 1.49 (95% confidence interval [CI]: 1.23–1.79) in men and 1.50 (1.10–2.04) in women. High cholesterol (≥6.21 mmol/L) was not a risk factor. This association was unchanged in analyses that excluded deaths due to liver disease, which yielded age-adjusted HRs of 1.38 (95% CI, 1.13–1.67) in men and 1.49 (1.09–2.04) in women. The multivariate-adjusted HRs and 95% CIs of the lowest cholesterol group for hemorrhagic stroke, heart failure (excluding myocardial infarction), and cancer mortality significantly higher than those of the moderate cholesterol group, for each cause of death. Conclusions: Low cholesterol was related to high mortality even after excluding deaths due to liver disease from the analysis. High cholesterol was not a risk factor for mortality.
Background: In 2008, the Japanese government implemented a program of health lifestyle interventions to reduce health care expenditure. This study evaluated whether these interventions decreased health care expenditures. Methods: The study enrolled 99 participants insured by Japanese National Health Insurance, who, in our previous study conducted in 2004, were allocated by random sampling into an intervention group (50 participants) and a control group (49 participants). In the intervention group, we used a health support method that facilitated the attainment of goals established by each participant. The control group received instruction in exercise, as well as health support using publically available media. Although 3 participants in the intervention group and 9 participants in the control group did not participate in a follow-up health examination 1 year after the intervention, the health care expenditures of all initial participants were assessed. Expenditures before and after the intervention were compared within and between groups. Data on health care expenditures were obtained from inpatient, outpatient, pharmacy, and dental health insurance claims. Results: After the intervention, the pharmacy and dental expenditures were significantly higher in the intervention group, while the pharmacy expenditure was significantly higher in the control group. However, there was no significant difference in any medical expenditure item between the intervention and control groups before or after the intervention. Conclusions: No significant differences were observed in short-term medical expenses for any medical expenditure item after a lifestyle intervention.