Insomnia and risk of nonalcoholic fatty liver disease: A systematic review and meta-analysis

AIM: This sudy aims to investigate the association between insomnia or excessive daytime sleepiness (EDS) and risk of nonalcoholic fatty liver disease (NAFLD). METHODS: We searched published studies indexed in MEDLINE and EMBASE database from inception to December 2015. Studies that reported odds ratios (ORs), risk ratios, hazard ratios or standardized incidence ratio with 95% confidence intervals (CI) comparing the risk of NAFLD among participants who had insomnia or EDS versus those without insomnia or EDS were included. Pooled ORs and 95% CI were calculated using a random-effect, generic inverse variance method of DerSimonian and Laird. Cochran's Q test and I(2) statistic were used to determine the between-study heterogeneity. RESULTS: Our search strategy yielded 2117 potentially relevant articles (781 articles from MEDLINE and 1336 articles from EMBASE). After comprehensive review, seven studies (three cross-sectional studies and four case–control studies) were found to be eligible and were included in the meta-analysis. The risk of NAFLD in participants who had insomnia was significantly higher with the pooled OR of 1.13 (95% CI, 1.00–1.27). The statistical heterogeneity was moderate with an I(2) of 62%. Elevated risk of NAFLD was also observed among participants with EDS even though the 95% CI was wider and did not reach statistical significance (pooled OR 2.21; 95% CI, 0.84–5.82). The statistical heterogeneity was moderate with an I(2) of 62%. CONCLUSIONS: Our study demonstrated an increased risk of NAFLD among participants who had insomnia or EDS. Whether this association is causal needs further investigations.