Non-Alcoholic Fatty Liver Disease (NAFLD) is one of the most common causes of chronic liver disease worldwide. There is no universally accepted effective treatment for NAFLD. Although various studies propose statins effective in lowering liver enzymes and in improving liver histology, their potency in the treatment and development of NAFLD remains unknown.

We conducted this meta-analysis to evaluate the efficacy of statins in the treatment and the development of NAFLD.

Electronic databases (MEDLINE and Cochrane CENTRAL) were searched from their inception until May 2021 for observational studies and randomized controlled trials (RCTs) that assessed the efficacy of statins for the treatment of NAFLD and its development. Studies were included irrespective of the dosage or duration, and their risk of bias was assessed. The outcomes of interest for our study were the effect of statins on liver histology (steatosis, fibrosis and necroinflammation, NAFLD activity score [NAS]) and liver enzymes (Alanine transaminase [ALT], Aspartate transaminase [AST], and Gamma-glutamyl transferase [GGT] levels). To pool continuous outcomes, a random-effects model was used to derive weighted mean difference (WMD) or standardized mean difference (SMD) and their corresponding 95% confidence intervals (CIs). Generic inverse variance was then used for different measurement units reported by the studies. For studies investigating the effects of statins on the development of NAFLD, generic inverse variance along with random effects model was used to derive odds ratio (ORs) and its corresponding 95% confidence interval (CI).

A total of 14 studies including 1,247,503 participants were short-listed for our analysis. All the studies included in our analysis had a low to moderate risk of bias. The results of our analysis suggest that statins may significantly reduce the risk of developing NAFLD (OR:0.69, 95% CI [0.57,0.84]; p = 0.0002; I² =36%). Statin use significantly reduced ALT levels (WMD: -27.28, 95% CI [-43.06, -11.51]; p = 0.0007; I² =90%), AST levels (WMD: -10.99, 95% CI [-18.17, -3.81]; p = 0.003; I² =79%) and GGT levels (WMD: -23.40, 95% CI [-31.82, -14.98]; p < 0.00001; I² = 21%) in patients presenting with NAFLD at baseline. In liver histology outcomes, steatosis grade (SMD: -2.59, 95% CI [-4.61, -0.56]; p = 0.01; I² = 95%), NAS (WMD: -1.03, 95% CI [-1.33, -0.74]; p < 0.00001; I² = 33%), necro-inflammatory stage (WMD: -0.19, 95% CI [-0.26, -0.13]; p < 0.00001; I² = 0%) and significant fibrosis (OR:0.20, 95% CI [0.04, 0.95]; p = 0.04; I² = 97%) underwent notable reduction. However, fibrosis stage outcome (WMD: 0.07, 95% CI [-0.05, 0.20]; p = 0.27; I² = 0%) was non-significant.

There was a significant decrease in transaminase and transferase levels. Marked improvement in liver histology of NAFLD patients was observed. Statin use also remarkably reduced the risk of developing NAFLD. Future large-scale trials can further aid in identifying the positive impact of statins in treatment for NAFLD and those at risk of developing it.