a nested case-control study Chinese meta-analysis.

Results from previous prospective studies assessing the relation between adiponectin and type 2 diabetes (T2D) were not entirely consistent, and evidence in Chinese population is scarce. Moreover, the last meta-analysis did not examine the impact of metabolic variables on the adiponectin-T2D association. Therefore, we prospectively evaluated the adiponectin-T2D association among 571 T2D cases and 571 age-sex-matched controls nested within the Singapore Chinese Health Study (SCHS). Furthermore, we conducted an updated meta-analysis by searching prospective studies on Pubmed till September 2016. In the SCHS, the odds ratio of T2D, comparing the highest versus lowest tertile of adiponectin levels, was 0.30 (95% confidence interval: 0.17, 0.55) in the fully-adjusted model. The relation was stronger among heavier participants (body mass index ≥ 23 kg/m 2 ) compared to their leaner counterparts ( P for interaction = 0.041). In a meta-analysis of 34 prospective studies, the pooled relative risk was 0.53 (95% confidence interval: 0.47, 0.61) comparing the extreme tertiles of adiponectin with moderate heterogeneity ( I 2 = 48.7%, P = 0.001). The adiponectin-T2D association remained unchanged after adjusting for inflammation and dyslipidemia markers, but substantially attenuated with adjustment for insulin sensitivity and/or glycaemia markers. Overall evidence indicates that higher adiponectin levels are associated with decreased T2D risk in Chinese and other populations. a major adipokine tissue attracted much attention due to its anti-inflammatory and insulin-sensitizing properties as well as its beneficial role in glucose metabolism 2 . Animal studies and experimental studies have shown that adiponectin improves insulin sensitivity 3,4 , thus may prevent the development of type 2 diabetes (T2D). A meta-analysis in year 2009 summarized data from 13 prospec- tive studies in various populations, and confirmed an inverse association between adiponectin levels and T2D risk 5 , since then, many more studies have been published with variability in the strength of the adiponectin-T2D association 6–23 . Most of the previous studies have been conducted in the Western populations, and a few were conducted among Asian populations such as Japanese, Indians and Koreans. Chinese have lower adiponectin levels compared to other ethnic groups 24 . Meanwhile, Chinese are also particularly sensitive to the detrimental metabolic effects of greater body fatness 25 . So far only a relatively small study (76 T2D cases) has examined the materials and comparability between we transformed the originally reported RRs (per per SD, per log increment, quartiles or quintiles) to a uniform comparison involving extreme tertiles of adiponectin levels using standard statistical methods which were described previously 51,52 . When RRs were reported in subgroups rather than the total sample in a study, a within-study RR was attained first using a fixed-effect analysis. RRs and corresponding 95% CIs were pooled by the DerSimonian-Laird random-effects models 53 , and fixed-effect models were used in sensitivity analyses. Between-study heterogeneity was evaluated by Cochran χ 2 and I 2 Statistic 54 . Meta-regression analyses were used to examine the influence of certain factors on observed associations, includ- ing location, ethnicity, age, sex, follow-up duration, number of T2D cases, adiponectin assay, ascertainment of T2D, level of adjustment, and study quality. Stratified analyses were performed to evaluate the influences of base- line participant characteristics on the results. Potential for publication bias was examined by Egger’s test 55 . To detect any nonlinear association, restricted cubic spline regression model with three knots at 25%, 50% and 75% percentiles adiponectin distribution was applied. When the nonlinear hypothesis was rejected, a two-stage, log-linear, dose-response regression function was then used for both the fixed-effect and random-effect models to estimate the risk of T2D per 5 µ g/mL increment in adiponectin levels 56 . Studies which reported case number, total number of participants, as well as adiponectin median value in each category were included in the dose-response meta-analysis. All P values were two-sided, and data were analyzed with STATA version 14 (Stata Corp, College Station, Texas).