Objective: To assess the effect of long-term exposure to air pollution on type 2 diabetes risk, a meta-analysis of prospective cohort studies was performed. Methods: Literature search was conducted with Pubmed, Embase, and Web of Science for prospective cohort studies investigating the association of type 2 diabetes risk with increments in particulate matter (PM, diameter !2.5 mm (PM2.5) or !10 mm (PM10)) or nitrogen dioxide (NO 2 ). We used a random-effects model to calculate the overall relative risk (RR) with 95% CI. Results: Of 808 identified articles, ten cohort studies were finally included, which involved a total of 2 371 907 participants and 21 095 incident cases of type 2 diabetes. Elevated risk of type 2 diabetes was significantly associated with long-term exposures to high levels of PM2.5 (RRZ1.28, 95% CI 1.06-1.55, PZ0.009, I2 Z83.5%), PM10 (RRZ1.15, 95% CI 1.02-1.30, PZ0.022, I2 Z0%), and NO 2 (RRZ1.12, 95% CI 1.02-1.23, PZ0.015, I 2 Z63.5%). When using standardized risk estimates, the RRs of type 2 diabetes were significant for increments in concentrations of PM2.5 (1.39 per 10 mg/m 3 increment, 95% CI 1.14-1.68, PZ0.001), PM10 (1.34 per 10 mg/m 3 increment, 95% CI 1.22-1.47, P!0.001), and NO 2 (1.11 per 10 mg/m 3 increment, 95% CI 1.07-1.16, P!0.001). No obvious evidence of publication bias was observed. Conclusion: Long-term exposure to high levels of main air pollutants is significantly associated with elevated risk of type 2 diabetes mellitus.

Diabetes is an independent risk factor for vertebral fracture, primarily being due to diabetic osteoporosis.

Tumor necrosis factor-α (TNF-α) is a cell signaling protein involved in systemic inflammation, and is also an important cytokine in the acute phase reaction. Several studies suggested a possible association between TNF-α and diabetic peripheral neuropathy (DPN) in type 2 diabetic patients, but no accurate conclusion was available. A systematic review and meta-analysis of observational studies was performed to comprehensively assess the association between serum TNF-α levels and DPN in type 2 diabetic patients. We searched Pubmed, Web of Science, Embase, and China Biology Medicine (CMB) databases for eligible studies. Study-specific data were combined using meta-analysis. Fourteen studies were finally included into the meta-analysis, which involved a total of 2650 participants. Meta-analysis showed that there were obviously increased serum TNF-α levels in DPN patients compared with type 2 diabetic patients without DPN (standard mean difference [SMD] = 1.203, 95 % CI 0.795-1.611, P < 0.001). There were also obviously increased levels of serum TNF-α in diabetic patients with DPN when compared with healthy controls (SMD = 2.364, 95 % CI 1.333-3.394, P < 0.001). In addition, there were increased serum TNF-α levels in painful DPN patients compared with painless DPN patients (SMD = 0.964, 95 % CI 0.237-1.690, P = 0.009). High level of serum TNF-α was significantly associated with increased risk of DPN in patients with type 2 diabetes (odds ratio [OR] = 2.594, 95 % CI 1.182-5.500, P = 0.017). Increased serum levels of TNF-α was not associated with increased risk of painful DPN in patients with type 2 diabetes (OR = 2.486, 95 % CI 0.672-9.193, P = 0.172). Sensitivity analysis showed that there was no obvious change in the pooled estimates when omitting single study by turns. Type 2 diabetic patients with peripheral neuropathy have obviously increased serum TNF-α levels than type 2 diabetic patients without peripheral neuropathy and healthy controls, and high level of serum TNF-α may be associated with increased risk of peripheral neuropathy independently. Further prospective cohort studies are needed to assess the association between TNF-α and DPN.

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While several epidemiological studies have investigated the relationship between height and risk for thyroid cancer, the results were inconsistent. In the present study, a systematic review and meta-analysis of prospective cohort studies was conducted to assess the impact of height on thyroid cancer risk. Online databases were searched up to December 30, 2014, for prospective cohort studies on the association between height and thyroid cancer risk. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random-effects model of meta-analysis. In all, 11 articles were included in this meta-analysis, including 15 prospective cohort studies, containing 6,695,593 participants and 7,062 cases of thyroid cancer. By comparing the highest versus the lowest categories of height, we reported that risk of thyroid cancer was increased with height in both men (summary RR 5 1.40, 95%CI 1.09-1.78, p 5 0.008) and women (summary RR 5 1.54, 95%CI 1.30-1.83, p < 0.001). The summary RR of thyroid cancer per 5-cm increase in height was 1.16 (95%CI 1.09-1.23, p < 0.001). The results were similar among men (per 5-cm increase RR 5 1.13, 95%CI 1.03-1.23, p 5 0.011) and women (per 5-cm increase RR 5 1.18, 95%CI 1.10-1.27, p < 0.001). No obvious risk of publication bias was observed. Our meta-analysis provides strong evidence for a dose-response relationship between height and risk of thyroid cancer in both men and women.

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