PURPOSE: Previous observational epidemiological studies have reported inconsistent findings on the association between dietary intake of omega-3 fatty acids and endocrine-related gynecological cancer such as ovarian cancer and endometrial cancer. This study aimed to investigate this association using a meta-analysis of observational studies. MATERIALS AND METHODS: We searched PubMed, EMBASE, and Cochrane library by using key words related with the topic in April 2017. The pooled odd ratios (pORs), relative risks (pRRs), or hazard ratios (pHRs) with 95% confidence intervals (CIs) were calculated based on the random-effects model. Also, we performed subgroup meta-analysis by methodological quality, types of cancer, study design, and omega-3 fatty acids. RESULTS: A total of ten observational studies with six case-control and four cohort studies were included in the final meta-analysis. In the meta-analysis of all the studies, dietary intake of total omega-3 fatty acids was not significantly associated with the risk of endometrial and ovarian cancers (pOR/HR, 0.87; 95% CI, 0.73-1.04; I²=67.2%) (highest versus lowest intake). In the subgroup meta-analysis by type of study, there was no significant association between them in cohort studies (pHR, 1.03; 95% CI, 0.63-1.67, I²=81.9%), whereas its reduced risk was observed in case-control studies (pOR, 0.81; 95% CI, 0.67 to 0.98, I²=55.7%). CONCLUSION: The current meta-analysis of observational studies suggests that there is no higher level of evidence to support the protective effect of dietary omega-3 fatty acids on endocrine-related gynecological cancer. Further prospective studies should be conducted to confirm the association.
Case-Control Studies ; Cohort Studies ; Endometrial Neoplasms ; Epidemiologic Studies ; Fatty Acids, Omega-3 ; Female ; Observational Study ; Ovarian Neoplasms ; Prospective Studies

BACKGROUND/AIMS: Some observational epidemiologic studies have reported conflicting results on the relationship between hypnotics use and the risk of developing and/or dying from heart disease. We investigated these associations using a meta-analysis of available literatures. METHODS: We searched the databases PubMed and EMBASE, along with the bibliographies of relevant articles to find additional publications in February 2016. RESULTS: Of 495 articles satisfying our initial criteria, two case-control studies and six cohort studies met our inclusion criteria and were included in the final analyses. Compared with never having used any kind of hypnotics, the odds ratio for overall use was 0.84 for risk of or mortality from heart disease (95% confidence interval, 0.79 to 0.89) in a random-effects meta-analysis of all eight studies. With respect to the geographical region, use of hypnotics was associated with a decreased risk or mortality of heart disease in Asia but not in Western countries. Among various types of sleep medications, zolpidem showed a decreased risk (–29%) of developing or dying from heart disease, but benzodiazepines were related with an increased risk (80%) of or mortality from heart disease. CONCLUSIONS: The current meta-analysis of observational epidemiological studies suggested an evidence of association between hypnotics use and a decreased risk of heart disease.
Asia ; Benzodiazepines ; Case-Control Studies ; Cohort Studies ; Epidemiologic Studies ; Heart Diseases* ; Heart* ; Hypnotics and Sedatives* ; Mortality* ; Observational Study ; Odds Ratio

BACKGROUND: Previous observational epidemiological studies have shown inconsistent results on the relationship between hypnotics use and risk of cancer. To determine the association between hypnotics use and risk of cancer, we conducted a meta-analysis of available literature. METHODS: We searched databases PubMed, EMBASE, and the bibliographies of relevant articles to locate additional publications in February 2016. Three evaluators independently reviewed and selected eligible studies based on pre-determined selection criteria. RESULTS: A total of six observational epidemiological studies including three case-control studies and three cohort studies, which involved 1,830,434 participants (202,629 hypnotics users and 1,627,805 non-users), were included in the final analyses. In a random-effects meta-analysis, compared with non-use of hypnotics, the odds ratio for overall hypnotics use was 1.29 for various cancers (95% confidence interval, 1.08–1.53). Subgroup meta-analyses by various factors such as study design, type of case-control study, study region, and methodological quality of study revealed consistent findings. CONCLUSION: Our findings from a meta-analysis of low-biased epidemiological studies suggested evidence linking the use of hypnotics to an increased risk of cancers. The results should be cautiously interpreted because of considerable heterogeneity with a Higgins I2 value.
Case-Control Studies ; Cohort Studies ; Epidemiologic Studies ; Hypnotics and Sedatives* ; Observational Study ; Odds Ratio ; Patient Selection ; Population Characteristics

Two common study designs of occupational epidemiologic studies are cohort mortality studies, which use the population at risk as a denominator, and proportionate mortality studies, which use the total number of events as a denominator. This study compared the various methods of point estimation for cohort mortality studies, i.e., RR (risk ratio), OR (odds ratio) and SMR (standardized mortality ratio), and those for proportionate mortality studies, i.e., PRR (proportionate risk ratio), POR (proportionate odds ratio) and PMR (proportionate mortality ratio). This study was based on a real dataset of all workers in Metropolitan Toronto, Canada, who applied for compensation for various types of injuries or diseases from the Workers' Compensation Board in 1980. Results showed that within the cohort mortality or proportionate mortality study designs, OR (or POR) in all cases gave the least conservative estimates (farthest away from the null value), while SMR (or PMR) gave the most conservative estimates. The empirical differences between the point estimators were generally small. Our results showed that between study designs the corresponding point estimators were poorly correlated. In addition, this empirical study indicated that the use of the mortality odds ratio did not improve the proportionate mortality study very much in terms of generating results similar to the risk ratio from the cohort mortality design. We drew two conclusions: first, the point estimators within each study design can generally be a good alternative to one another; and second, proportionate mortality studies are not a good approximation for cohort mortality studies.
Cohort Studies ; Comparative Study ; Cross-Sectional Studies ; Epidemiologic Methods* ; Human ; Mortality* ; Occupational Exposure/adverse effects*

BACKGROUND: Fetuin-A is a hepatokine that involved in the pathogenesis of insulin resistance. Previous epidemiological studies have found a positive association between blood fetuin-A and type 2 diabetes mellitus (T2DM) risk among Caucasians and African Americans. We aimed to investigate the prospective relationship between fetuin-A and T2DM in an Asian population for the first time. METHODS: A nested case-control study was established within a prospective cohort of Chinese living in Singapore. At blood collection (1999 to 2004), all participants were free of diagnosed T2DM and aged 50 to 79 years. At subsequent follow-up (2006 to 2010), 558 people reported to have T2DM and were classified as incident cases, and 558 controls were randomly chosen from the participants who did not develop T2DM to match with cases on age, sex, dialect group, and date of blood collection. Plasma fetuin-A levels were measured retrospectively in cases and controls using samples collected at baseline. Conditional logistic regression models were used to compute the odds ratio (OR) and 95% confidence interval (CI). Restricted cubic spline analysis was used to examine a potential non-linear association between fetuin-A levels and T2DM risk. RESULTS: Compared with those in the lowest fetuin-A quintile, participants in the highest quintile had a two-fold increased risk of developing T2DM (OR, 2.06; 95% CI, 1.21 to 3.51). A non-linear association was observed (P nonlinearity=0.005), where the association between fetuin-A levels and T2DM risk plateaued at plasma concentrations around 830 µg/mL. CONCLUSION: There is a positive association between plasma fetuin-A levels and risk of developing T2DM in this Chinese population.
African Americans ; alpha-2-HS-Glycoprotein ; Asian Continental Ancestry Group ; Case-Control Studies ; Cohort Studies ; Diabetes Mellitus, Type 2 ; Epidemiologic Studies ; Epidemiology ; Follow-Up Studies ; Humans ; Insulin Resistance ; Logistic Models ; Odds Ratio ; Plasma ; Prospective Studies ; Retrospective Studies ; Singapore

BACKGROUND: Neck and shoulder pain is fairly common among adolescents in Korea and results in significant health problem. The aims of this prospective study was to identify the effects of education, in terms of recognition of this issue and posture correction, on prevalence and severity of neck and shoulder pain in Korean adolescents. METHODS: A prospective, observational cohort design was used. The 912 students from two academic high schools in the city of Seoul were eligible for the current study and 887 completed this study. After a baseline cross-sectional survey, students listened to a lecture about cervical health, focusing on good posture, habits, and stretching exercises to protect the spine, and were encouraged by their teachers to keep the appropriate position. And follow-ups were conducted 3 months later, to evaluate the effect of education. RESULTS: The prevalence of neck and shoulder pain was decreased 19.5% (from 82.5 to 66.4%). The baseline mean usual and worst numeric rating scale were 19.9/100 (95% CI, 18.1-21.7) and 31.2/100 (95% CI, 28.7-33.2), respectively. On the follow-up survey, the mean usual and worst numeric rating scale were decreased significantly by 24.1 and 21.7%, respectively, compared with baseline (P < 0.01). Of the 570 students reporting neck and shoulder pain, 16.4% responded that they had experienced improvement during the 3 months. CONCLUSIONS: Education; recognition of this issue and posture correction, for cervical health appeared to be effective in decreasing the prevalence and severity of neck and shoulder pain at a 3 month follow-up.
Adolescent* ; Cohort Studies ; Cross-Sectional Studies ; Education* ; Exercise ; Follow-Up Studies ; Humans ; Korea ; Longitudinal Studies* ; Neck Pain ; Neck* ; Posture ; Prevalence* ; Prospective Studies ; Seoul ; Shoulder Pain* ; Spine

This study aimed to assess whether night shift work is associated with the risk of depression by using a meta-analysis of observational studies. We searched PubMed and EMBASE in August, 2016 to locate eligible studies and investigated the association between night shift work and the risk of depression, reporting outcome measures with adjusted odds ratios (ORs) or relative risks (RRs) and 95% confidence intervals (CIs). In the meta-analysis of a total of 11 observational studies with 9 cross-sectional study, 1 longitudinal study, and 1 cohort study, night shift work was significantly associated with an increased risk of depression (OR/RR, 1.43; 95% CI, 1.24–1.64; I² = 78.0%). Also, subgroup meta-analyses by gender, night shift work duration, type of occupation, continent, and type of publication showed that night shift work was consistently associated with the increased risk of depression. The current meta-analysis suggests that night shift work is associated with the increased risk of depression. However, further large prospective cohort studies are needed to confirm this association.
Cohort Studies ; Cross-Sectional Studies ; Depression* ; Longitudinal Studies ; Observational Study ; Occupations ; Odds Ratio ; Outcome Assessment (Health Care) ; Prospective Studies ; Publications

BACKGROUND AND PURPOSE: Previous studies have reported conflicting results about the prevalence of seizures in Alzheimer's disease (AD). There are few epidemiological studies on this topic in Asia. Thus, the objective of this study was to examine demographic and clinical characteristics as well as incidence for seizures in AD patients compared to non-AD patients in a prospective, longitudinal, community-based cohort with a long follow-up. METHODS: Data were collected from National Health Insurance Service-National Elderly Cohort (NHIS-elderly) Database to define patients with AD from 2004–2006 using Korean Classification Diseases codes G30 and F00. We performed a 1:5 case-control propensity score matching based on age, sex, and household income. We conducted Cox proportional hazards regression analysis to estimate the risk of epilepsy in AD patients. RESULTS: In the cohort study, patients with AD had higher risk for epilepsy than those without AD, with hazard ratio of 2.773 (95% confidence interval [CI], 2.515–3.057). This study also showed that male gender and comorbidities such as hypertension, hyperlipidemia, diabetes, and chronic kidney disease increased the risk of developing epilepsy. Patients with AD had 1.527 (95% CI, 1.375–1.695) times higher mortality rate than those in the control group. CONCLUSIONS: AD patients have significantly higher risk of developing epilepsy than non-AD patients.
Aged ; Alzheimer Disease* ; Asia ; Case-Control Studies ; Classification ; Cohort Studies* ; Comorbidity ; Epidemiologic Studies ; Epilepsy* ; Family Characteristics ; Follow-Up Studies ; Humans ; Hyperlipidemias ; Hypertension ; Incidence ; Male ; Mortality ; National Health Programs ; Prevalence ; Propensity Score ; Prospective Studies ; Renal Insufficiency, Chronic ; Seizures

OBJECTIVE: The results of epidemiological studies investigated the association between polycystic ovary syndrome (PCOS) and the breast cancer are inconsistent. This meta-analysis was conducted to estimate the association between PCOS and the breast cancer risk. We searched PubMed, Web of Science, and Scopus for observational studies until June 2015. Data were independently extracted and analyzed using 95% odds ratio, and confidence intervals (CIs) based on the random-effects models. METHODS: We identified 970 references and conducted eight studies with 45,470 participants and 243,064 person- year. RESULTS: The association between PCOS and the breast cancer risk in case-control studies 0.87 (95% CI, 0.44 to 1.31) and that of cohort studies was estimated 1.18 (95% CI, 0.93 to 1.43). CONCLUSION: This meta-analysis demonstrated that PCOS no does increase the risk of breast cancer. Further prospective cohort studies are needed to provide convincing evidence in order to PCOS can increase or not effect on the risk of the breast cancer.
Breast Neoplasms* ; Breast* ; Case-Control Studies ; Cohort Studies ; Epidemiologic Studies ; Odds Ratio ; Polycystic Ovary Syndrome* ; Prospective Studies

OBJECTIVE: The results of epidemiological studies investigated the association between polycystic ovary syndrome (PCOS) and the breast cancer are inconsistent. This meta-analysis was conducted to estimate the association between PCOS and the breast cancer risk. We searched PubMed, Web of Science, and Scopus for observational studies until June 2015. Data were independently extracted and analyzed using 95% odds ratio, and confidence intervals (CIs) based on the random-effects models. METHODS: We identified 970 references and conducted eight studies with 45,470 participants and 243,064 person- year. RESULTS: The association between PCOS and the breast cancer risk in case-control studies 0.87 (95% CI, 0.44 to 1.31) and that of cohort studies was estimated 1.18 (95% CI, 0.93 to 1.43). CONCLUSION: This meta-analysis demonstrated that PCOS no does increase the risk of breast cancer. Further prospective cohort studies are needed to provide convincing evidence in order to PCOS can increase or not effect on the risk of the breast cancer.
Breast Neoplasms* ; Breast* ; Case-Control Studies ; Cohort Studies ; Epidemiologic Studies ; Odds Ratio ; Polycystic Ovary Syndrome* ; Prospective Studies