To evaluate the long-term consequences of coffee drinking in patients with type 2 diabetes.
PubMed, Scopus, and Web of Sciences were searched to November 2020 for prospective cohort studies evaluating the association of coffee drinking with risk of cardiovascular disease (CVD) and mortality in patients with type 2 diabetes. Two reviewers extracted data and rated the certainty of evidence using GRADE approach. Random-effects models were used to estimate the hazard ratios (HRs) and 95% CIs. Dose-response associations were modeled by a one-stage mixed-effects meta-analysis. Ten prospective cohort studies with 82,270 cases were included. Compared to those with no coffee consumption, the HRs for consumption of 4 cups/d were 0.79 (95%CI: 0.72, 0.87; n = 10 studies) for all-cause mortality, 0.60 (95%CI: 0.46, 0.79; n = 4) for CVD mortality, 0.68 (95%CI: 0.51, 0.91; n = 3) for coronary heart disease (CHD) mortality, 0.72 (95%CI: 0.54, 0.98; n = 2) for CHD, and 0.77 (95%CI: 0.61, 0.98; n = 2) for total CVD events. There was no significant association for cancer mortality and stroke. There was an inverse monotonic association between coffee drinking and all-cause and CVD mortality, and inverse linear association for CHD and total CVD events. The certainty of evidence was graded moderate for all-cause mortality, and low or very low for other outcomes.
Drinking coffee may be inversely associated with the risk of mortality in patients with type 2 diabetes. However, more research is needed considering type of coffee, sugar and cream added to coffee, and history of CVD to present more confident results.