Whether metabolic syndrome is a risk factor of colorectal adenoma has spurred debate. We systematically meta-analyzed all clinical studies associated with metabolic syndrome (MetS)/metabolic components and colorectal adenoma risk and quantified the dose-response association between them, aiming to provide more clues for better decision-making.

We searched PubMed, EMBASE, and Cochrane Library through June 2020 for clinical studies of MetS and colorectal adenoma risk. RevMan 5.3 software and STATA 12.0 software were employed for meta-analysis.

Seventeen studies representing 44,336 participants were eligible for analysis. The overall meta-analysis showed that MetS patients had increased risk of colorectal adenoma (OR: 1.39, 95% CI 1.24–1.57; P < 0.05). Dose-response analysis presented that every increased number of Mets components was associated with a 8% increment of colorectal adenoma risk(OR: 1.08; 95% CI: 1.04–1.11). Subgroup analysis by age revealed a higher colorectal adenoma risk in MetS patients 50 years or older (OR 1.46; 95% CI 1.21–1.76; P < 0.0001), rather than MetS patients younger than 50 years old (OR 1.23; 95% CI 0.95–1.59; P = 0.11).When stratified by sex, the analysis revealed a higher risk of colorectal adenoma in male MetS patients (OR 1.32; 95% CI 1.15–1.53; P = 0.0001), rather than females (OR 1.65; 95% CI 0.90–3.02; P = 0.10). The analysis split by adenoma location showed that the right colon (OR 1.35; 95% CI 1.04–1.75; P = 0.03), instead of the left colon (OR 1.16; 95% CI 0.84–1.59; P = 0.37) or rectum(OR 1.26; 95% CI 0.89–1.78; P = 0.20), was the predilection site associated with increased colorectal adenoma risk in MetS patients.

Overall, our meta-analysis showed that MetS was associated with a higher risk of colorectal adenoma. MetS patients, especially old (≥50 years) male patients, should be a risk population for colorectal adenoma screening so that they can benefit from behavioural interventions that can help prevent the development of colorectal cancer.