Combined lifestyle factors and risk of incident type 2 diabetes and prognosis among individuals with type 2 diabetes: a systematic review and meta-analysis of prospective cohort studies

A healthy lifestyle has been widely recommended for the prevention and management of type 2 diabetes. However, no systematic review has summarised the relationship between combined lifestyle factors (including, but not limited to, smoking, alcohol drinking, physical activity, diet and being overweight or obese) and incident type 2 diabetes and risk of health outcomes among diabetic individuals. EMBASE and PubMed were searched up to April 2019 without language restrictions. References included in articles in relevant publications were also screened. Cohort studies investigating the combined associations of at least three lifestyle factors with incident type 2 diabetes and health outcomes among diabetic individuals were included. Reviewers were paired and independently screened studies, extracted data and evaluated study quality. Random-effects models were used to calculate summary HRs. Heterogeneity and publication bias tests were also conducted. Compared with participants considered to have the least-healthy lifestyle, those with the healthiest lifestyle had a 75% lower risk of incident diabetes (HR 0.25 [95% CI 0.18, 0.35]; 14 studies with approximately 1 million participants). The associations were largely consistent and significant among individuals from different socioeconomic backgrounds and baseline characteristics. Among individuals with type 2 diabetes (10 studies with 34,385 participants), the HRs (95% CIs) were 0.44 (0.33, 0.60) for all-cause death, 0.51 (0.30, 0.86) for cardiovascular death, 0.69 (0.47, 1.00) for cancer death and 0.48 (0.37, 0.63) for incident cardiovascular disease when comparing the healthiest lifestyle with the least-healthy lifestyle. Adoption of a healthy lifestyle is associated with substantial risk reduction in type 2 diabetes and long-term adverse outcomes among diabetic individuals. Tackling multiple risk factors, instead of concentrating on one certain lifestyle factor, should be the cornerstone for reducing the global burden of type 2 diabetes.