Aim
This systematic review and meta-analysis aimed to clarify whether tobacco smoking is associated with an increased risk of diverticular disease.

Method
The PubMed and Embase databases were searched for studies of smoking and diverticular disease up to 19 February 2016. Prospective studies that reported adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of diverticular disease associated with current or previous smoking were included. Summary RRs were estimated using a random effects model.

Results
We identified five prospective studies which comprised 6076 cases of incident diverticular disease (diverticulosis and diverticulitis) among 385 291 participants and three studies with 1118 cases of complications related to diverticular disease (abscess or perforation) among 292 965. The summary RR for incident diverticular disease was 1.36 (95% CI 1.15–1.61, I2 = 84%, n = 4) for current smokers, 1.17 (95% CI 1.05–1.31, I2 = 49%, n = 4) for former smokers and 1.29 (95% CI 1.16–1.44, I2 = 62%, n = 5) for ever smokers. The summary RR was 1.11 (95% CI 0.99–1.25, I2 = 82%, n = 4) per 10 cigarettes per day. Although there was some indication of nonlinearity there was a dose-dependent positive association with increasing number of cigarettes smoked per day. There was some evidence that smoking also increases the risk of complications of diverticular disease, but the number of studies was small.

Conclusion
The current meta-analysis provides evidence that tobacco smoking is associated with an increased incidence of diverticular disease and related complications.