Dairy Products,Dietary Calcium and Vitamin D Intake as Risk Factors for Prostate Cancer: A Meta-Analysis of 26,769 Cases From 45 Observational Studies

In this study, we examined the available evidence and sources of heterogeneity for studies of dairy products, calcium, and vitamin D intake and the risk of prostate cancer. We pooled data from 45 observational studies using a general variance-based, meta-analytic method employing CIs. Summary relative risks (RRs) were calculated for specific dairy products such as milk and dairy micronutrients. Sensitivity analyses were performed to test the robustness of these summary measures of effect. Cohort studies showed no evidence of an association between dairy [RR = 1.06; 95% confidence interval (CI) = 0.92–1.22] or milk intake (RR = 1.06; 95% CI = 0.91–1.23) and risk of prostate cancer. This was supported by pooled results of case-control analyses (RR = 1.14; 95% CI = 1.00–1.29), although studies using milk as the exposure of interest were heterogeneous and could not be combined. Calcium data from cohort studies were heterogeneous. Case-control analyses using calcium as the exposure of interest demonstrated no association with increased risk of prostate cancer (RR = 1.04; 95% CI = 0.90–1.15). Dietary intake of vitamin D also was not related to prostate cancer risk (RR = 1.16; 95% CI = 0.98–1.38). The data from observational studies do not support an association between dairy product use and an increased risk of prostate cancer.     

Coffee Consumption and Prostate Cancer Risk: A Meta-Analysis of Cohort Studies

This meta-analysis was conducted to assess the association between coffee consumption and prostate cancer risk. Thirteen cohort studies with 34,105 cases and 539,577 participants were included in the meta-analysis. The summary relative risks (RRs) with 95% confidence intervals (CIs) for different coffee intake levels were calculated. Dose-response relationship was assessed using generalized least square trend estimation. The pooled RR for the highest vs. lowest coffee intake was 0.90 (95% CI: 0.85–0.95), with no significant heterogeneity across studies (P = 0.267; I²= 17.5%). The dose-response analysis showed a lower cancer risk decreased by 2.5% (RR = 0.975; 95% CI: 0.957–0.995) for every 2 cups/day increment in coffee consumption. Stratifying by geographic region, there was a statistically significant protective influence of coffee on prostate cancer risk among European populations. In subgroup analysis of prostate cancer grade, the summary RRs were 0.89 (95% CI: 0.83–0.96) for nonadvanced, 0.82 (95% CI: 0.61–1.10) for advanced and 0.76 (95% CI: 0.55–1.06) for fatal diseases. Our findings suggest that coffee consumption may be associated with a reduced risk of prostate cancer and it also has an inverse association with nonadvanced prostate cancer. Because of the limited number of studies, more prospective studies with large sample size are needed to confirm this association.     

Dairy products, dietary calcium and vitamin D intake as risk factors for prostate cancer: a meta-analysis of 26,769 cases from 45 observational studies

In this study, we examined the available evidence and sources of heterogeneity for studies of dairy products, calcium, and vitamin D intake and the risk of prostate cancer. We pooled data from 45 observational studies using a general variance-based, meta-analytic method employing CIs. Summary relative risks (RRs) were calculated for specific dairy products such as milk and dairy micronutrients. Sensitivity analyses were performed to test the robustness of these summary measures of effect. Cohort studies showed no evidence of an association between dairy [RR = 1.06; 95% confidence interval (CI) = 0.92-1.22] or milk intake (RR = 1.06; 95% CI = 0.91-1.23) and risk of prostate cancer. This was supported by pooled results of case-control analyses (RR = 1.14; 95% CI = 1.00-1.29), although studies using milk as the exposure of interest were heterogeneous and could not be combined. Calcium data from cohort studies were heterogeneous. Case-control analyses using calcium as the exposure of interest demonstrated no association with increased risk of prostate cancer (RR = 1.04; 95% CI = 0.90-1.15). Dietary intake of vitamin D also was not related to prostate cancer risk (RR = 1.16; 95% CI = 0.98-1.38). The data from observational studies do not support an association between dairy product use and an increased risk of prostate cancer.     

Dairy Consumption and Gastric Cancer Risk: A Meta-Analysis of Epidemiological Studies

Studies investigating the association of dairy consumption with gastric cancer risk have reported inconsistent findings. We conducted this systematic review and meta-analysis to review and summarize the epidemiologic evidence on the relation of total dairy and milk consumption with risk of gastric cancer. We summarized the available literature on this topic using meta-analysis of relative risks (RR) associated with total dairy and milk intake. The total of 17 case-control and 6 cohort studies (3256 cases) were eligible for inclusion. When comparing the highest with the lowest category of total dairy intake, the results of cohort studies indicated that increased consumption of total dairy food was associated with a reduced risk of gastric cancer (RR = 0.76; 95% CI: 0.64–0.91), whereas case-control studies provided no association. In subgroup analysis, significantly inverse associations between total diary food consumption and gastric cancer risk were observed in Europe subgroup (RR = 0.73; 95% CI: 0.54–0.99), U.S. subgroup (RR = 0.78; 95% CI: 0.63–0.98) but not in Asia subgroup. However, milk consumption was not associated with gastric cancer risk no matter in main or subgroup analysis. The results of cohort studies, but not case-control studies, suggested that total dairy might be related to the reduction of gastric cancer risk. Milk consumption was not associated with gastric cancer risk.     

Citrus fruits intake and prostate cancer risk: a quantitative systematic review

OBJECTIVES: The purpose of this systematic review was to investigate the association between dietary intake of citrus fruits and prostate cancer risk. METHODS: Authors searched electronic databases and the reference lists of publications of diet and prostate cancer studies until August 2007. All of the epidemiological studies that obtained individual data on dietary intake of citrus fruits and presented risk estimates of the association between intake of citrus fruits and risk of prostate cancer were identified and included. Using general variance-based methods, study-specific odds ratios (OR)/ relative risk (RR) and associated confidence interval (CI)/ standard error (SE) for highest versus lowest intake of citrus fruits level were extracted from each paper. RESULTS: Eleven articles including six case-control studies, one nested case-control study and four cohort studies, proved eligible. Overall summary OR using random effect model did not show an association in risk of prostate cancer with intake of citrus fruits (summary OR=1.03, 95% CI=0.89-1.19) with large heterogeneity across studies that we were unable to explain (I(2)=67.88%). The summary ORs in case-control studies and cohort studies were 1.10 (95% CI=0.97-1.22) and 1.05 (95% CI=0.96-1.14), respectively. CONCLUSIONS: Pooled results from observational studies did not show an association between intake of citrus fruits and the risk of prostate cancer, although results vary substantially across studies.     

Glycemic index, glycemic load and endometrial cancer risk: results from the Australian National Endometrial Cancer study and an updated systematic review and meta-analysis

Purpose

The relationship between habitual consumption of foods with a high glycemic index (GI) and/or a diet with a high glycemic load (GL) and risk of endometrial cancer is uncertain, and relatively few studies have investigated these associations. The objectives of this study were to examine the association between GI/GL and risk of endometrial cancer using data from an Australian population-based case–control study and systematically review all the available evidence to quantify the magnitude of the association using meta-analysis.

Methods

The case–control study included 1,290 women aged 18–79 years with newly diagnosed, histologically confirmed endometrial cancer and 1,436 population controls. Controls were selected to match the expected Australian state of residence and age distribution (in 5-year bands) of cases. For the systematic review, relevant studies were identified by searching PubMed and Embase databases through to July 2011. Random-effects models were used to calculate the summary risk estimates, overall and dose–response.

Results

In our case–control study, we observed a modest positive association between high dietary GI (OR 1.43, 95 % CI 1.11–1.83) and risk of endometrial cancer, but no association with high dietary GL (OR 1.15, 95 % CI 0.90–1.48). For the meta-analysis, we collated information from six cohort and two case–control studies, involving a total of 5,569 cases. The pooled OR for the highest versus the lowest intake category of GI was 1.15 (0.95–1.40); however, there was significant heterogeneity (p 0.004) by study design (RR 1.00 [95 % CI 0.87–1.14] for cohort studies and 1.56 [95 % CI 1.21–2.02] for case–control studies). There was no association in the dose–response meta-analysis of GI (RR per 5 unit/day increment of GI 1.00, 95 % CI 0.97–1.03). GL was positively associated with endometrial cancer. The pooled RR for the highest versus the lowest GL intake was 1.21 (95 % CI 1.09–1.33) and 1.06 (95 % CI 1.01–1.11) per 50 unit/day increment of GL in the dose–response meta-analysis.

Conclusion

The pooled results from observational studies, including our case–control results, provide evidence of a modest positive association between high GL, but not GI, and endometrial cancer risk.     

Physical activity, diabetes, and risk of thyroid cancer: a systematic review and meta-analysis

Thyroid cancer incidence has been increasing more rapidly over time than the occurrence of cancers of other sites, and interest in potential adverse relations of diabetes and lack of physical activity to thyroid cancer risk is accumulating. We conducted a systematic review and meta-analysis of published epidemiologic studies on the relations of physical activity and diabetes to thyroid cancer according to the Meta-analysis of Observational Studies in Epidemiology guidelines. Published studies were identified through a search in MEDLINE and EMBASE. Random-effects models were used to summarize thyroid cancer risk estimates comparing high versus low levels of physical activity, and separately, comparing individuals with diabetes versus those without diabetes. Meta-regression analyses were performed to evaluate potential effect modification by study design and thyroid cancer risk factors. Information was extracted from seven studies of physical activity and thyroid cancer and from six studies of diabetes and thyroid cancer. The number of individuals from studies on physical activity was 939,305 (yielding 2,250 incident thyroid cancer cases) and from studies on diabetes it was 960,840 (yielding 1,230 cases). The summary relative risk (RR) estimate from cohort and case–control studies combined indicated no association between physical activity and thyroid cancer (summary RR 1.06, 95 % confidence interval (CI) 0.79–1.42). Subgroup-analyses revealed a significant positive association between physical activity and thyroid cancer in cohort studies (summary RR 1.28; 95 % CI 1.01–1.63), whereas the relation was suggestively inverse in case–control studies (summary RR 0.70; 95 % CI 0.48–1.03; p for heterogeneity = 0.005). Individuals with diabetes showed a borderline statistically significant increased risk of thyroid cancer compared with those without diabetes (summary RR 1.17; 95 % CI 0.99–1.39). The relations of physical activity and diabetes to thyroid cancer were not modified by sex, number of adjustment factors, and adjustments for adiposity, smoking, and study quality. In this comprehensive systematic review and meta-analysis, no significant association between physical activity and thyroid cancer was found. Diabetes showed a suggestive positive relation with risk of thyroid cancer.     

Dietary fiber intake and risk of type 2 diabetes: a dose–response analysis of prospective studies

Observational studies suggest an association between dietary fiber intake and risk of type 2 diabetes, but the results are inconclusive. We conducted a meta-analysis of prospective studies evaluating the associations of dietary fiber intake and risk of type 2 diabetes. Relevant studies were identified by searching EMBASE (from 1974 to April 2013) and PubMed (from 1966 to April 2013). The fixed or random-effect model was selected based on the homogeneity test among studies. In addition, a 2-stage random-effects dose–response meta-analysis was performed. We identified 17 prospective cohort studies of dietary fiber intake and risk of type 2 diabetes involving 19,033 cases and 488,293 participants. The combined RR (95 % CI) of type 2 diabetes for intake of total dietary fiber, cereal fiber, fruit fiber and insoluble fiber was 0.81 (0.73–0.90), 0.77 (0.69–0.85), 0.94 (0.88–0.99) and 0.75 (0.63–0.89), respectively. A nonlinear relationship was found of total dietary fiber intake with risk of type 2 diabetes (P _{for nonlinearity} < 0.01), and the RRs (95 % CI) of type 2 diabetes were 0.98 (0.90–1.06), 0.97 (0.87–1.07), 0.89 (0.80–0.99), 0.76 (0.65–0.88), and 0.66 (0.53–0.82) for 15, 20, 25, 30, and 35 g/day. The departure from nonlinear relationship was not significant (P _{for nonlinearity} = 0.72), and the risk of type 2 diabetes decreased by 6 % (RR 0.94, 95 % CI 0.93–0.96) for 2 g/day increment in cereal fiber intake. Findings from this meta-analysis indicate that the intakes of dietary fiber may be inversely associated with risk of type 2 diabetes.     

Long-chain omega-3 polyunsaturated fatty acids and risk of stroke: a meta-analysis

Prospective studies of long-chain omega-3 polyunsaturated fatty acids (PUFA) in relation to stroke have yielded inconsistent results. The authors conducted a meta-analysis of prospective studies to summarize available evidence regarding the relation between long-chain omega-3 PUFA intake and stroke. Pertinent studies were identified by searching PubMed and Embase databases to November 1, 2012 and by reviewing the reference lists of relevant publications. Prospective studies that provided relative risks (RRs) with 95 % confidence intervals (CIs) for the association between dietary long-chain omega-3 PUFA intake and stroke were eligible. A random-effects model was used to combine study-specific results. Eight prospective studies, with 5238 stroke events among 242,076 participants, were included in the meta-analysis. The combined RR of total stroke was 0.90 (95 % CI, 0.81–1.01) for the highest versus lowest category of long-chain omega-3 PUFA intake, without heterogeneity among studies (P = 0.32). Results were similar for ischemic (RR, 0.82; 95 % CI, 0.71–0.94) and hemorrhagic stroke (RR, 0.80; 95 % CI, 0.55–1.15). A statistically significant reduction in total stroke risk was observed in women (RR, 0.80; 95 % CI, 0.65–0.99). This meta-analysis showed no overall association between omega-3 PUFA intake and stroke, but suggests that women might benefit from a higher intake of these PUFAs.     

Tobacco smoking and the risk of sudden cardiac death: a systematic review and meta-analysis of prospective studies

Smoking is an established risk factor for cardiovascular disease including coronary heart disease and stroke, however, data regarding smoking and sudden cardiac death have not been summarized in a meta-analysis previously. We therefore conducted a systematic review and meta-analysis to clarify this association. We searched the PubMed and Embase databases for studies of smoking and sudden cardiac death up to July 20th 2017. Prospective studies were included if they reported adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) for smoking and sudden cardiac death. Summary RRs were estimated by use of a random effects model. Twelve prospective studies were included. The summary RR was 3.06 (95% CI 2.46–3.82, I² = 41%, p_{heterogeneity} = 0.12, n = 7) for current smokers and 1.38 (95% CI 1.20–1.60, I² = 0%, p_{heterogeneity} = 0.55, n = 7) for former smokers compared to never smokers. For four studies using non-current (never + former) smokers as the reference category the summary RR among current smokers was 2.08 (95% CI 1.70–2.53, I² = 18%, p_{heterogeneity} = 0.30). The results persisted in most of the subgroup analyses. There was no evidence of publication bias. These results confirm that smoking increases the risk of sudden cardiac death. Any further studies should investigate in more detail the effects of duration of smoking, number of cigarettes per day, pack-years, and time since quitting smoking and sudden cardiac death.     

A meta-analysis of prospective studies of coffee consumption and mortality for all causes, cancers and cardiovascular diseases

Several prospective studies considered the relation between coffee consumption and mortality. Most studies, however, were underpowered to detect an association, since they included relatively few deaths. To obtain quantitative overall estimates, we combined all published data from prospective studies on the relation of coffee with mortality for all causes, all cancers, cardiovascular disease (CVD), coronary/ischemic heart disease (CHD/IHD) and stroke. A bibliography search, updated to January 2013, was carried out in PubMed and Embase to identify prospective observational studies providing quantitative estimates on mortality from all causes, cancer, CVD, CHD/IHD or stroke in relation to coffee consumption. A systematic review and meta-analysis was conducted to estimate overall relative risks (RR) and 95 % confidence intervals (CI) using random-effects models. The pooled RRs of all cause mortality for the study-specific highest versus low (≤1 cup/day) coffee drinking categories were 0.88 (95 % CI 0.84–0.93) based on all the 23 studies, and 0.87 (95 % CI 0.82–0.93) for the 19 smoking adjusting studies. The combined RRs for CVD mortality were 0.89 (95 % CI 0.77–1.02, 17 smoking adjusting studies) for the highest versus low drinking and 0.98 (95 % CI 0.95–1.00, 16 studies) for the increment of 1 cup/day. Compared with low drinking, the RRs for the highest consumption of coffee were 0.95 (95 % CI 0.78–1.15, 12 smoking adjusting studies) for CHD/IHD, 0.95 (95 % CI 0.70–1.29, 6 studies) for stroke, and 1.03 (95 % CI 0.97–1.10, 10 studies) for all cancers. This meta-analysis provides quantitative evidence that coffee intake is inversely related to all cause and, probably, CVD mortality.     

Coffee Drinking and the Risk of Endometrial Cancer: An Updated Meta-Analysis of Observational Studies

Background: Several compounds contained in coffee have been found to suppress carcinogenesis in experimental studies. We conducted a dose–response meta-analysis to assess the impact of coffee consumption on the risk of endometrial cancer. Materials and methods: We searched MEDLINE and EMBASE databases for studies published up to August 2016. Using random effects models, we estimated summary relative risks (RR) for cohort studies and odds ratios (OR) for case-control studies with 95% confidence intervals (CI). Dose–response analyses were conducted by using generalized least square trend estimation. Results: We identified 12 cohort studies and 8 case-control studies eligible for inclusion, contributing with 11,663 and 2,746 endometrial cancer cases, respectively. The summary RR for highest compared with lowest coffee intake was 0.74 (95% CI: 0.68–0.81; p_{heterogeneity} = 0.09, I² = 32%). The corresponding summary RR among cohort studies was 0.78 (95% CI: 0.71–0.85; p_{heterogeneity} = 0.14, I² = 31.9%) and 0.63 (95% CI: 0.53–0.76; p_{heterogeneity} = 0.57, I² = 0%) for case-control studies. One-cup increment per day was associated with 3% risk reduction (95% CI: 2–4%) in cohort studies and 12% (95% CI: 5–18%) in case-control studies. After pooling the results from 5 cohort studies, the association remained significant only in women with body mass index over 30 (RR = 0.71, 95% CI: 0.61–0.81). Conclusion: The results from our meta-analysis strengthen the evidence of a protective effect of coffee consumption on the risk of EC and further suggest that increased coffee intake might be particularly beneficial for women with obesity.     

Body fatness,diabetes, physical activity and risk of kidney stones: a systematic review and meta-analysis of cohort studies

We conducted a systematic review and meta-analysis to clarify the association between adiposity, diabetes, and physical activity and the risk of kidney stones. PubMed and Embase were searched up to April 22nd 2018 for relevant studies. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random effects models. Thirteen cohort studies were included. The summary relative risk was 1.21 (95% CI 1.12–1.30, I²?=?76%, n?=?8) per 5 unit increment in BMI, 1.16 (95% CI 1.12–1.19, I²?=?0%, n?=?5) per 10 cm increase in waist circumference, 1.06 (95% CI 1.04–1.08, I²?=?67%, n?=?3) per 5 kg increase in weight and 1.12 (95% CI 1.06–1.18, I²?=?86%, n?=?3) per 5 kg of weight gain. The summary RR was 1.16 (95% CI 1.03–1.31, I²?=?51%, n?=?10) for participants with diabetes compared to participants without diabetes, and 0.93 (95% CI 0.78–1.10, I²?=?80%, n?=?4) for high vs. low physical activity. These results suggest a positive association between adiposity and diabetes and the risk of kidney stones, but no association with physical activity.     

Dietary Fat Intake and the Risk of Skin Cancer: A Systematic Review and Meta-Analysis of Observational Studies

Abstract

We conducted a meta-analysis to evaluate the association between fat intake and the risk of three major types of skin cancer including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM). A comprehensive search of PubMed and EMBASE was performed to identify all relevant observational studies published up to December 1, 2018. Specific odds ratio (OR) or relative risk (RR) estimates for the highest versus the lowest intake of dietary fat and 95% confidence intervals (CI) from the included studies were pooled using random effect model. Three prospective cohort studies (175,675 participants and 30,915 BCC cases, 4,106 SCC cases and 1,638 CMM cases) and nine case-control studies (328 BCC cases, 493 SCC cases, 1,547 CMM cases and 2,660 controls) were identified. The pooled results indicated that dietary consumption of total fat and saturated fat were not associated with three major types of skin cancer. High consumption of monounsaturated fat was significantly associated with a decreased risk of BCC (RR: 0.90, 95% CI: 0.85–0.96) and high level of polyunsaturated fat intake was potentially positively associated with SCC (RR: 1.19, 95% CI: 1.06–1.33). Our findings should be confirmed by further evidence from well-designed and large-scale prospective cohort studies.     

Dietary Fat Consumption and Non-Hodgkin's Lymphoma Risk: A Meta-analysis

Objective: Many studies suggest that high-fat diets are linked to the etiology of non-Hodgkin's lymphoma (NHL). However, the findings are inconsistent and therefore the association between fat and non-Hodgkin's lymphoma remains unclear. In this study, we aim to quantitatively assess the association between fat consumption and the risk for NHL. Methods: We reviewed 221 published cohort and case-control studies that reported relative risk (RRs) and corresponding 95% confidence intervals (CIs) of NHL and fat intake using PubMed, Cochrane, EMBASE, and Google Scholar databases. A random-effects model computed summary risk estimates. Results: Based on our literature search, 10 of 221 studies (two cohort and eight case-control studies) were relevant to this meta-analysis. There was a significant association between total fat consumption and increased risk of NHL (RR = 1.26; 95% CI: 1.12–1.42); in addition, subgroup analysis showed a significant correlation with diffuse large B-cell lymphoma (RR = 1.41; 95% CI: 1.08–1.84) but not with follicular lymphoma (RR = 1.21; 95% CI: 0.97–1.52), small lymphocytic lymphoma/chronic lymphocytic leukemia (RR = 0.91; 95% CI: 0.68–1.23), nor with T cell lymphoma (RR = 1.12; 95% CI: 0.60–2.09). The funnel plot revealed no evidence for publication bias. Conclusion: Total fat consumption, particularly animal fat, increases the risk for NHL.     

Dietary Magnesium Intake and Risk of Cancer: A Meta-Analysis of Epidemiologic Studies

The aim of this study was to investigate the association between dietary magnesium and the risk of overall cancer using a meta-analysis. We searched PubMed, SCOPUS, and the Cochrane Review through November 2012. All the articles searched were independently reviewed by 3 authors based on predetermined selection criterion. A total of 13 epidemiologic studies, 6 case-control studies, and 7 prospective cohort studies involving 1,236,004 participants were included in the final analysis. When all studies were pooled, the relative risk (RR) of overall cancer for the highest level of dietary magnesium intake was 0.801 [95% confidence interval (CI): 0.664–0.966) compared with the lowest level of dietary magnesium intake. In subgroup meta-analyses by study design, there was a significant inverse association between dietary magnesium and the risk of cancer in case-control studies (RR = 0.663, 95% CI: 0.475–0.925), whereas there was no significant association in prospective cohort studies (RR = 0.888, 95% CI: 0.745–1.060). Furthermore, there was a significant preventive effect of dietary magnesium for colorectal cancer (RR = 0.775, 95% CI: 0.655–0.919), but not for other cancer. Our meta-analysis showed that higher dietary magnesium intake seems to have a protective effect for cancer, especially colorectal cancer and in females.     

Effects of Serum Triglycerides on Prostate Cancer and Breast Cancer Risk: A Meta-Analysis of Prospective Studies

Epidemiological studies show conflicting results regarding the link between serum triglyceride and the risk of prostate cancer and breast cancer. Therefore, we performed a meta-analysis of prospective studies to clarify this association. We searched PubMed, EMBASE, the Chinese Biomedical Database (CBM), and the China National Knowledge Infrastructure (CNKI) database to identify relevant prospective studies of the relationship between serum triglyceride and prostate cancer and breast cancer risk. Study-specific estimates adjusting for potential confounders were combined to evaluate a summary relative risks (RRs) and 95% confidence intervals (95% CIs) using a fixed- or random-effects model. A total of 11 prospective studies (619,410 subjects and 15,691 incident prostate cancer patients) and 8 prospective studies (590,878 subjects and 12,177 incident breast cancer patients) were respectively included in our meta-analysis to assess the associations of serum triglyceride with prostate cancer and breast cancer risk. The pooled adjusted RR estimates for prostate cancer and breast cancer for the highest versus the lowest exposure levels of serum triglycerides were 0.95 (95% CI: 0.87–1.04) and 0.94 (95% CI: 0.87–1.00), respectively. Additionally, a dose–response analysis revealed that serum levels of triglycerides were not associated with the risk of prostate cancer and breast cancer. We found that serum triglyceride was not related to the risk of prostate cancer and breast cancer.     

Citrus fruit intake and bladder cancer risk: a meta-analysis of observational studies

Epidemiological studies have investigated the association between citrus fruit and bladder cancer risk; however, the results are inconsistent. To assess these issues, we conducted a meta-analysis of currently available studies. We identified relevant articles by searching the MEDLINE and EMBASE databases. We calculated the summary relative risk (RR) with 95% confidence interval (95% CI) using a random effect model. We included eight case–control studies and six cohort studies in the meta-analysis. There was a significant inverse association between citrus fruit intake and bladder cancer risk in all pooled studies (RR: 0.85; 95% CI, 0.76–0.94) and case–control studies (RR: 0.77; 95% CI, 0.64–0.92), but not in the cohort studies (RR: 0.96; 95% CI, 0.87–1.07). Our results suggest that citrus fruit intake is related to decreased bladder cancer risk. Subsequent well-designed, large prospective studies are needed to obtain better understanding of this relationship.     

Dietary fiber consumption and risk of stroke

Observational studies suggest an association between dietary fiber consumption and risk of stroke, but the results are inconclusive. The authors conducted a meta-analysis of prospective cohort studies to evaluate the relation between dietary fiber consumption and stroke risk and mortality. Relevant studies were identified by searching PubMed, Embase, and ISI Web of Science through February 2013. We included prospective studies that reported relative risks (RRs) with 95 % confidence intervals (CIs) for the association between dietary fiber consumption and stroke risk and mortality. Both fixed- and random-effects models were used to calculate the summary risk estimates. Eleven prospective studies involving 325,627 participants were included in the meta-analysis. The pooled RR of stroke for the highest compared with the lowest dietary fiber consumption was 0.83 (95 % CI 0.74, 0.93). In addition, the increment in dietary fiber consumption was associated with decreased stroke risk in a dose–response manner. Sensitivity analysis restricted to studies with control for conventional risk factors yielded similar results, and omission of any single study had little effect on the combined risk estimate. Moreover, there was a trend toward an inverse association between higher fiber consumption and stroke mortality (RR 0.85; 95 % CI 0.60, 1.20), although it is not significant. This meta-analysis indicated that dietary fiber consumption is inversely associated with stroke risk, and the effect is probably independent of conventional risk factors. Our results support recommendations for higher consumption of fiber-rich foods to prevent stroke.     

Personal hair dye use and bladder cancer: a meta-analysis

Despite considerable research, the issue of hair dyes and bladder cancer is still open to discussion. In January 2013, we searched in PubMed/EMBASE to identify observational studies investigating the association between personal use of hair dyes and bladder cancer incidence/mortality. Pooled relative risks (RRs) and corresponding 95% confidence intervals (CIs) were calculated using random-effects models. Fifteen case-control and two cohort studies were available for meta-analysis (8504 cases/deaths, 14,102 controls, and 617,937 persons at risk). Compared with no use, the pooled RR of bladder cancer for personal use of any type of hair dyes was 0.93 (95% CI, 0.82–1.05), with moderate heterogeneity among studies (I² = 34.1%, P = .07). Similar RRs were found for females (RR = 0.95) and males (RR = 0.81). Based on seven studies, the pooled RR for personal use of permanent hair dyes was 0.92 (95% CI, 0.77–1.09). Compared with no use, no association was observed for the highest categories of duration of use and lifetime frequency of use of both any type of dyes and permanent dyes. The pooled RR from four studies reporting results for use of dark-colored dyes was 1.29 (95% CI, 0.98–1.71). This meta-analysis allows to definitively exclude any appreciable excess risk of bladder cancer among personal hair dye users.