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BACKGROUND: Although short adult height is generally associated with increased risks of type 2 diabetes mellitus (T2DM), there are large inconsistencies across studies. The aims of this study were to describe and quantify currently available evidence on the association between adult height and T2DM, to examine whether the reported associations differ by sex, and to examine the shapes of the height and T2DM associations.METHODS: Relevant literature was identified using PubMed (1966-May 2018), EMBASE (1947-May 2018) and Google Scholar (May 2018). We identified cross-sectional and cohort studies with original publications on human subjects, which were included in a random-effects meta-analysis.RESULTS: From 15 971 identified sources, 25 studies met the inclusion criteria for the systematic review (N=401 562 individuals). From these 25 studies, 16 (9 cross-sectional studies and 7 cohort studies) were included in the meta-analysis (n=261 496 individuals). The overall random-effects meta-analysis indicated an inverse association between adult height and T2DM (effect estimate=0.88, 95% CI 0.81 to 0.95). No sex differences in the associations between adult height and T2DM were found (effect estimate for men: 0.86, 95% CI 0.75 to 0.99; effect estimate for women: 0.90; 95% CI 0.80 to 1.01; p value for sex interaction=0.80). Due to lack of data, results on the shape of the association between height and T2DM were inconclusive.CONCLUSIONS: Shorter height is associated with an increased risk of T2DM and the association does not significantly differ by sex. The currently available data are insufficient to support conclusions regarding the shape of the association between height and T2DM.TRIAL REGISTRATION NUMBER: CRD42017062446.

We conducted a systematic review and meta-analysis of observational studies investigating the association between antibiotic exposure in infancy and risk of childhood overweight and obesity. Thirteen studies counting a total of 527,504 children were included in the systematic review and eight were included in meta-analyses. Exposure to antibiotics in infancy was associated with an increased odds ratio (OR) of childhood overweight and obesity (OR = 1.11 [95% CI 1.02-1.20]). Whereas exposure to one treatment only and exposure between 6 and 24 months were not associated with increased risk of childhood overweight and obesity, exposure to more than one treatment was associated with an OR of 1.24 (95% CI 1.09-1.43) and exposure within the first six months of life was associated with an OR of 1.20 (95% CI 1.04-1.37). In conclusion, antibiotic exposure in infancy is associated with a slightly increased risk of childhood overweight and obesity, mainly if children are exposed to repeated treatments or treatment within the first six months of life. It remains elusive whether this association is mediated via direct effects of antibiotics on the gut microbiota.