Passive Smoking in Childhood Associated With Increased Risk for Adult Fatty Liver

Prevention of exposure to passive cigarette smoking should begin as early as possible, as exposure in childhood appears to be associated with an increased risk for fatty liver in adulthood, according to a study published in the American Journal of Gastroenterology.

Nonalcoholic fatty liver disease is the most common cause of chronic liver disease. Identifying risk factors early in life is important for its prevention. Data are lacking on the longitudinal influence of childhood passive smoking on the risk for fatty liver as an adult. In an attempt to fill these gaps, researchers used data from a 31-year prospective, population-based cohort study to examine the relationship between passive smoking in children and adults with adult risk for fatty liver.

Data were taken from the Cardiovascular Risk in Young Finns Study national register. Researchers collected data from 1315 participants who did not actively smoke in childhood or adulthood, but retained complete data on passive smoking in childhood (parental smoking) in 1980 and 1983; participants were aged 3 to 18 years during 1980. Adulthood passive smoking was assessed in 2001, 2007, and 2011. Fatty liver was determined by ultrasound in 2011, when participants were aged 34 to 49 years.

The researchers found that the prevalence of fatty liver was 16.3% (n=215) in this population. Those who developed fatty liver were more often men, were of more advanced age, had higher body mass index (BMI) and insulin levels at both time points, and had higher adult systolic blood pressure, triglycerides, and alcohol consumption, but lower levels of physical activity.  

Both child and adult passive smoking were associated with an increased risk for fatty liver in adulthood (childhood: relative risk [RR], 1.41; 95% CI, 1.01-1.97; adulthood: RR, 1.35; 95% CI, 1.01-1.82). Adult risk factors which linked childhood passive smoking to adult fatty liver included BMI (proportion of association mediated = 20.2%) and serum triglycerides (15.1%); adult risk factors linking adulthood passive smoking to adult fatty liver included BMI (51.2%), waist circumference (44.1%), and insulin levels (7.6%).  

Individuals with persistent exposure to passive smoking between childhood and adulthood had the highest risk for adult fatty liver (RR, 1.99; 95% CI, 1.14-3.45).

This study is not without limitations. Fatty liver during childhood was not measured. Additionally, per study protocol, fatty liver was diagnosed via ultrasound imaging; liver biopsy is considered the standard method for measuring fatty liver.

“These findings suggest that effective strategies for preventing passive smoking in both child and adult life may substantially reduce adult risk of fatty liver,” concluded the authors.

Reference

Wu F, Pahkala K, Juonala M, et al. Childhood and adulthood passive smoking and nonalcoholic fatty liver in midlife: a 31-year cohort study. Am J Gastroenterol. 2021;116(6):1256–1263. doi: 10.14309/ajg.0000000000001141