NAFLD Incidence, Prevalence Increasing Worldwide

Kiarash Riazi, MD

A new look at non-alcoholic fatty liver disease (NAFLD) data show the disease is increasing worldwide and remains especially high among men.

A team, led by Kiarash Riazi, MD, Division of Gastroenterology and Hepatology, Department of Medicine, Cumming School of Medicine, University of Calgary, examined the burden of NAFLD by estimating the temporal trends of worldwide prevalence and incidence.

Reviewing the Data

In the systematic review and meta-analysis, the investigators searched various databases between inception and May 25, 2021 for observational cross-sectional or longitudinal studies in patient populations representative of the general adult population for which NAFLD was diagnosed using an imaging method in absence of excessive alcohol consumption and viral hepatitis.

The investigators sought primary outcomes of the prevalence and incidence of NAFLD and used a random-effects meta-analysis to calculate overall and sex-specific pooled effect estimates and confidence intervals (CI).

Overall, they identified 28,557 total records, 13,577 of which were screened, with 299 records also identified through other methods. There was a total of 72 publications with a sample population of 1.03 million participants from 17 countries in the prevalence analysis.

There was also 16 publications with a sample population of 381,765 individuals from 5 countries in the incidence analysis.

Prevalence of NAFLD

Overall, the prevalence of NAFLD worldwide was 32.4% (95% CI, 29.9-34.9%). However, the prevalence of the disease has significantly increased over time, from 25.5% (95% CI, 20.1-31.0%) in or before 2005 to 37.8% (95% CI, 32.4-43.3%) in 2016 or later (P = 0.013).

The prevalence of disease was also higher in men (39.7%; 95% CI, 36.6-42.8%) than it was in women (25.6%; 95% CI, 22.3-28.8) (P <0.0001).

The Incidence Rate of NAFLD

The investigators also estimated an overall incidence of NAFLD of 46.9 cases per 1000 person-years. However, the incidence rate was higher in men (70.8 cases per 1000 person-years; 95% CI, 48.7-92.8) than it was in women (46.9 cases per 1000 person-years; 95% CI, 20.2-38.9) (P <0.0001).

There was also considerable heterogeneity between studies focused on NAFLD prevalence (I² = 99·9%) and NAFLD incidence ( I² = 99·9%).

“Worldwide prevalence of NAFLD is considerably higher than previously estimated and is continuing to increase at an alarming rate,” the authors wrote. “Incidence and prevalence of NAFLD are significantly higher among men than among women. Greater awareness of NAFLD and the development of cost-effective risk stratification strategies are warranted to address the growing burden of NAFLD.”

The Importance of Diet

Earlier this year, investigators found a higher adherence to the Dietary Approach to Stop Hypertension (DASH) diet had strong protection against incident NAFLD risk. On the other hand, higher scores in the Mediterranean diet study cohort had a weak, but inverse association with this same outcome.

The data show participants with higher DASH or Mediterranean Diet scores were mostly women with a mean age of 51 ± 9 years and were less likely to be current smokers, with lower BMI and abdominal adiposity at baseline.

A higher adherence to the DASH diet compared to a lower one was associated with 37% reduced risk of incident NAFLD (95% CI, 0.43-0.92) and a statistically significantly less increase in liver fat over study follow-up.

The study, “The prevalence and incidence of NAFLD worldwide: a systematic review and meta-analysis,” was published online in The Lancet Gastroenterology & Hepatology.