Nonalcoholic fatty liver disease associated with obstructive sleep apnea: just a coincidence?

BACKGROUND: Obesity is associated with obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease (NAFLD). It has been shown that OSA could be an independent risk factor for NAFLD. OSA could cause not only insulin resistance but worse NAFLD through nocturnal hypoxemia. This study aimed to evaluate the frequency of OSA and NAFLD in obese patients and the relationship between OSA, insulin resistance, and severity of steatohepatitis (nonalcoholic steatohepatitis (NASH)).

METHODS: Forty obese patients submitted to bariatric surgery were evaluated. Sleep studies, fasting blood glucose, serum insulin, homeostasis model assessment (HOMA-IR), and liver enzymes were measured. Liver biopsies were evaluated for features of NAFLD including degrees of steatosis, inflammation, cellular ballooning, and fibrosis. NASH was diagnosed in those with steatosis + ballooning or steatosis + fibrosis. The diagnosis of OSA was based on an apnea/hypopnea index (AHI) ≥ 5 events/hours.

RESULTS: OSA was present in 32 (80.0%), NAFLD in 33 (82.5%), and NASH in 32 (80.0%) patients. Patients with AHI ≥ 15 ev/h had higher serum insulin levels (30.0 ± 12.8 vs. 22.6 ± 17.3 μU/ml; p = 0.015) and HOMA-IR (7.5 ± 4.0 vs. 5.4 ± 4.1; p = 0.016) when compared with those with AHI < 15 ev/h, but no association was found between AHI and NASH (81.0% vs. 78.9%; p = 1.000) or oxihemoglobin desaturation <84% and NASH (81.2% vs. 70.8%; p = 0.709) when these groups were compared.

CONCLUSIONS: Obese patients had elevated OSA and NAFLD frequencies. OSA was associated with insulin resistance but not with the severity of NASH.