Serum C-peptide concentration and prostate cancer: A meta-analysis of observational studies.

BACKGROUND: The association between serum C-peptide concentration and prostate cancer remains unexplored. Therefore, we conducted a meta-analysis to assess whether C-peptide serum concentrations are associated with increased prostate cancer risk. METHODS: Several databases were searched to identify relevant original research articles published before November 2017. Random-effects models were used to summarize the overall estimate of the multivariable-adjusted odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: Nine observational studies involving 11,796 participants were identified. The findings of the meta-analysis indicated that the association between serum C-peptide concentration and prostate cancer was not significant (OR: 1.15, 95% CI: 0.85-1.54; for highest versus lowest category C-peptide concentrations, P = .376). The associations were inconsistent, as indicated by subgroup analyses. CONCLUSION: Although our findings provided no support for the hypothesis that serum C-peptide concentration is associated with excess risk of prostate cancer, people must pay attention to this aspect and increase physical activity or modify dietary habits to constrain insulin secretion, which possibly lead to decreased incidence of prostate cancer. Hence, well-designed observational studies involving different ethnic populations are still needed.

Association between cadmium exposure and urolithiasis risk: A systematic review and meta-analysis.

BACKGROUND: We performed a meta-analysis to determine whether a consistent relationship exists between cadmium exposure and urolithiasis in humans. Accordingly, we summarized and reviewed previously published quantitative studies. METHODS: Eligible studies with reference lists published before June 1, 2017 were obtained from searching several databases. Random effects models were used to summary the overall estimate of the multivariate adjusted odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: Six observational studies involving 88,045 participants were identified and stratified into the following categories according to cadmium assessment results: occupational (n = 4) and dietary (n = 2). The findings of the meta-analysis suggested that the risk of urolithiasis increases significantly by 1.32 times at higher cadmium exposure (OR = 1.32; 95% CI = 1.08-1.62; for highest vs lowest category urinary cadmium values). The summary OR in occupational exposure (OR = 1.56; 95% CI = 1.13-2.14) increased at the same condition. Meanwhile, no association was observed between cadmium exposure and urolithiasis risk in dietary exposure (OR = 1.13; 95% CI = 0.87-1.47). A significant association remained consistent, as indicated by subgroup analyses and sensitivity analyses. CONCLUSIONS: The meta-analysis indicated that increased risk of urolithiasis is associated with high cadmium exposure, and this association is higher in occupational exposure than in dietary exposure. Nevertheless, well-designed observational studies with different ethnic populations are still needed.

Association between butchers and cancer mortality and incidence: A systematic review and meta-analysis.

BACKGROUND: In this study, we evaluated whether increased risks of mortality and cancer incidence exist among butchers worldwide. To achieve this goal, we conducted a systematic review and meta-analysis to investigate the correlations of the risks of cancer death and incidence with male and female butchers. METHODS: We obtained data by performing a comprehensive literature search in several databases for eligible studies published before March 2017. Multivariable-adjusted standardized mortality ratios (SMRs) and odds ratio (OR), as well as associated 95% confidence intervals (CIs) and those by subgroups, were extracted and pooled. RESULTS: A total of 17 observational studies comprising 397,726 participants were included in the meta-analysis. The butcher occupation was not associated with all-cancer mortality risk, with pooled overall SMRs of 1.07 (95% CI 0.96-1.20). However, the pooled ORs revealed that butchers hold an elevated risk of total cancer incidence (OR, 1.51; 95% CI, 1.33-1.73). No proof of publication bias was obtained, and the findings were consistent in the subgroup analyses. CONCLUSION: Our results suggest that working as butchers did not significantly influence all-cancer mortality risk but significantly contributed to elevated all-cancer incidence risk. Nevertheless, well-designed observational studies on this topic are necessary to confirm and update our findings.

Vasectomy and cardiovascular disease risk: A systematic review and meta-analysis.

BACKGROUND: Even though several studies comparing vasectomy and cardiovascular disease (CVD) risk have been reported, most are small series with conflicting results. However, the extent of the risk is still uncertain. We therefore explored whether an association exists between vasectomy and CVD incidence and mortality. METHODS: We searched PubMed, Embase, Web of Science, and Cochrane Library databases for relevant studies published before January 2017. Multivariate adjusted odds ratio (OR) and associated 95% confidence intervals (CIs) and those by subgroups were extracted and pooled using random-effects models. RESULTS: Overall, 12 observational studies (2 cross-sectional studies, 4 case-control studies, and 6 retrospective cohort studies) comprising 299,436 participants were identified. There was no statistically significant relationship between vasectomy and CVD risk (OR: 0.90, 95% CI: 0.81-1.00). Moreover, vasectomy was not associated with CVD mortality (OR: 0.90, 95% CI: 0.81-1.00), coronary heart disease (CHD) incidence (OR: 0.94, 95% CI: 0.88-1.01), stroke incidence (OR: 0.90, 95% CI: 0.72-1.13), and myocardial infarction (MI) incidence (OR: 0.95, 95% CI: 0.88-1.02), with no significant publication bias. In subgroup analyses, the findings on the association between vasectomy and CVD risk were consistent. CONCLUSION: Our findings suggest that vasectomy is not associated with the excess risk of CVD incidence and mortality. Nevertheless, large-volume, well-designed observational studies, with different ethnic populations, low risk of bias, and adjusted confounding factors, are awaited to confirm and update the findings of this analysis.

Sleep problems and injury risk among juveniles: A systematic review and meta-analysis of observational studies.

Recent studies have reported inconsistent results regarding the association between sleep problems and injury risk among juveniles. Moreover, the extent of this risk remains largely unexplored. Thus, a systematic review and meta-analysis was conducted by our team to determine whether sleep problems increase the incidence of injuries among juveniles. PubMed, PsycINFO, Embase, and Cochrane Library databases were searched for relevant studies that explored the association between sleep problems and injury risk and have been published before July 2016. Multivariate adjusted odds ratio (OR) and associated 95% confidence intervals (CIs) were extracted and pooled using random-effects models. A total of 10 observational studies involving 73,418 participants were identified. Meta-analysis findings suggested that juveniles with sleep problems held a 1.64 times higher risk of injury than that of juveniles without sleep problems (OR: 1.64, 95% CI: 1.44-1.85). This relationship was also supported by subgroup analyses, which were based on different countries and study designs. The current evidence indicates that sleep problems are significantly associated with injury risk among juveniles. Sleep problems are highly important for young people; hence, sleep researchers and occupational physicians should focus on this aspect. Nevertheless, high-quality and adequately powered observational studies are still needed.