BackgroundChronic obstructive pulmonary disease (COPD) is set to become the third most frequent cause of death and also the third largest cause of global morbidity by 2020. In China, where the population is aging rapidly, COPD has become one of the leading causes of disability and a large economic burden. An epidemiological assessment of the COPD in China is required, with a focus on the number of cases living with disease, main determinants of the disease and time trends.MethodsWe systematically searched large Chinese bibliographic databases and English databases to identify spirometry–based epidemiological studies of the prevalence of COPD in China diagnosed according to GOLD criteria. We estimated age– and gender–specific prevalence of COPD using a multilevel mixed–effect logistic regression. We also presented the time trends of COPD between 1990 and 2010 by age, gender and setting (urban vs rural).FindingsIn 1990, the prevalence of COPD ranged from 0.49% (95% CI = 0.29–0.85) in <20 years group to 20.95% (95% CI = 14.04–27.04) in> = 80 years group, and the crude prevalence for China was 2.70% (95% CI = 1.86–3.51). In 2010, the prevalence in <20 years was 0.55% (95% CI = 0.37–1.04) and in> = 80 years was 22.89% (95% CI = 18.13–28.96), with the crude prevalence for China of 3.84% (95% CI = 3.30–4.77). The COPD prevalence in males was about two–fold higher than in females, and it increased with increasing age. Between 1990–2010, the total number of Chinese people living with COPD increased by 66.73%, from 30.90 million (95% CI = 21.28–40.02) in 1990 to 51.52 million (95% CI = 44.26–63.93) in 2010. This increase was most striking in middle age, and greater in females than in males from 30 years up to 64 years. Our estimates, which used an independent approach to acquiring data and development of analytical methods, and were based on a more complete data set, are remarkably similar to those produced recently by the GBD 2013 collaboration, differing by only about 5% in the estimated number of COPD cases in 1990 and by 1% in 2010.ConclusionsCOPD is a highly prevalent disease in China and its importance is growing steadily. The number of people living with COPD has increased substantially between 1990 and 2010. COPD is more frequent in males and in rural areas. Optimised primary and secondary prevention and treatment is urgently needed to counter this growing trend. Improved epidemiological studies will be required to assist development of more effective strategies of prevention and treatment of COPD in China in the next decade and beyond.

Background Low penetrance genetic variants, primarily single nucleotide polymorphisms, have substantial influence on colorectal cancer (CRC) susceptibility. Most CRCs develop from colorectal adenomas (CRA). Here, we report the first comprehensive field synopsis that catalogues all genetic association studies on CRA, with a parallel online database (http://www.chs.med.ed.ac.uk/CRAgene/). Methods We performed a systematic review, reviewing 9750 titles and then extracted data from 130 publications reporting on 181 polymorphisms in 74 genes. We conducted meta-analyses to derive summary effect estimates for 37 polymorphisms in 26 genes. We applied the Venice criteria and Bayesian False Discovery Probability (BFDP) to assess the levels of the credibility of associations. Results We considered the association with the rs6983267 variant at 8q24 as “highly credible”, reaching genome wide statistical significance in at least one meta-analysis model. We identified “less credible” associations (higher heterogeneity, lower statistical power, BFDP>0.02) with a further four variants of four independent genes: MTHFR c.677C>T p.A222V (rs1801133), TP53 c.215C>G p.R72P (rs1042522), NQO1 c.559C>T p.P187S (rs1800566), and NAT1 alleles imputed as fast acetylator genotypes. For the remaining 32 variants of 22 genes for which positive associations with CRA risk have been previously reported, the meta-analyses revealed no credible evidence to support these as true associations. Conclusions The limited number of credible associations between low penetrance genetic variants and CRA reflects the lower volume of evidence and associated lack of statistical power to detect associations of the magnitude typically observed for genetic variants and chronic diseases. The CRAgene database provides context for CRA genetic association data and will help inform future research directions.