Incidence and temporal trends of type 1 diabetes in China: a systematic review and meta-analysis

Abstract

BackgroundStudies of type 1 diabetes incidence in China have conflicting findings, and the epidemiology of type 1 diabetes in China is unclear. We aimed to assess the incidence and epidemiology of type 1 diabetes in relation to age, sex, and geographical area in mainland China. MethodsIn this systematic review and meta-analysis, we searched Pubmed (Jan 1, 1980, to May 18, 2016), Embase (Jan 1, 1980 to May 18, 2016), China National Knowledge Infrastructure (Jan 1, 1999, to May 20, 2016), and Wanfang Medical Database (Jan 1, 1998, to May 19, 2016) to identify population-based studies of type 1 diabetes incidence in mainland China. Only population-based studies with data on the incidence of type 1 diabetes in mainland China were included, and studies with overlapping data from included studies were excluded. We extracted data from the published reports and used random-effects meta-analysis to pool the incidence and incidence rate ratios (IRRs) with 95% CIs. We used the Q statistic and I2 method to assess heterogeneity, and also did subgroup analyses by sex, age, and geographical area. Additionally, we used time trends to explore the difference in incidence over time. This study is registered with PROSPERO, number CRD42016039284. FindingsWe identified 816 reports from the search and included 19 reports of population-based studies published between 1994 and 2015 in the analysis. Overall incidence of type 1 diabetes in mainland China was 0·74 (95% CI 0·55–1·00) per 100 000 person-years between 1980 and 2013. Incidence (per 100 000 person-years) increased rapidly from 0·57 (0·43–0·75) in 1990 to 1·04 (0·64–1·68) in 2000 and 3·36 (1·66–6·82) in 2010 (p<0·0001). The mean annual increase in incidence was 9·0% (5·1–15·9), and the increase was numerically higher in boys (10·6%, 95% CI 4·7–23·6) than in girls (7·2%, 2·7–18·8). Incidence was significantly higher in girls than in boys (IRR 1·23, 95% CI 1·12–1·36; p<0·0001), and this disparity was most profound in children aged 5–9 years (1·71, 1·27–2·29; p=0·00036). However, no obvious difference in incidence between boys and girls was seen in children aged 0–4 years (0·91, 0·70–1·18; p=0·46) and in those aged 10–14 years (1·09, 0·97–1·24; p=0·16). Using the age group of 0–4 years as reference, IRR increased from 2·21 (1·81–2·70; p<0·0001) for children aged 5–9 years to 2·99 (2·25–3·99; p<0·0001) for children aged 10–14 years. The IRR for urban versus rural areas was 1·82 (1·37–2·41; p=0·0001). InterpretationTo our knowledge, this is the first systematic review and meta-analysis to confirm the increasing incidence of type 1 diabetes over time in mainland China. Obvious disparities in incidence by sex, age, and geographical areas exist. FundingNational Natural Science Foundation of China (81471004).