Smoking raises the risk of fatty liver disease in adults in their 20s and 30s, regardless of obesity or alcohol consumption, according to a new study. The effect of smoking was even more pronounced among those with lean body types or who drank little alcohol.
According to the medical community on the 23rd, a joint research team led by Professor Ji Yong-ho of the Advanced Institute of Convergence Medicine at Ewha Womans University Seoul Hospital and Professor Shin Hyun-young of the Department of Family Medicine at the Catholic University of Korea's Seoul St. Mary's Hospital reached these findings. The team tracked big data from the National Health Insurance Service, following 3,496,144 Korean adults aged 20 to 39 who received health checkups between 2004 and 2007 through 2022. The analysis subjects consisted of 62% men and 38% women.
The research team determined the presence of fatty liver using the Fatty Liver Index (FLI), which reflects body mass index (BMI), waist circumference, and triglycerides. On a scale of 0 to 100, a score of 60 or higher is classified as indicating a high likelihood of fatty liver. The analysis found that men who smoked 20 or more cigarettes a day had a 41% higher risk of fatty liver, and those who had smoked for 10 to 19 years also had a 15% higher risk. Women had a lower smoking rate overall, but the fatty liver risk among those who smoked for 10 to 19 years increased by 55%, a larger increase than among men.
Of note are the conditions under which this association appears. The link between smoking and fatty liver was more clearly confirmed among groups with a BMI below 25 or daily alcohol intake below 25 grams. Conversely, the association weakened among groups that were obese or drank heavily. This is interpreted to mean that the risk from smoking alone operates independently, without being masked by other risk factors.
The research team explained that smoking is known to worsen insulin resistance and disrupt lipid metabolism, causing fat to accumulate in the liver. They added that it also triggers systemic inflammation and oxidative stress, and that nicotine stimulates the sympathetic nervous system, which can affect the progression of fatty liver and liver fibrosis. "We have identified the complex effects that lifestyle habits such as smoking, obesity, and drinking have on the liver health of young adults, and we will develop predictive models and prevention strategies that allow for early intervention at the health checkup stage," Professor Ji said.
The study was published in the latest issue of the Journal of Gastroenterology and Hepatology, an international academic journal in the field of gastroenterology and hepatology.
