Childhood Sedentariness May Cause Premature Liver Damage in Young Adulthood

Children who are sedentary for more than six waking hours a day have a significantly increased risk of severe fatty liver disease and liver cirrhosis by young adulthood, according to a study presented at ENDO 2024 and published in Nature’s npj Gut and Liver.

“We found that this relationship between sedentariness and liver damage is likely causal,” says study author Andrew Agbaje, MD, MPH, PhD, of the University of Eastern Finland in Kuopio, Finland.

Agbaje points out in his article that evidence on the long-term relationship of sedentary time (ST), light physical activity (LPA) and moderate-to-vigorous PA (MVPA) with liver steatosis, fibrosis, cirrhosis, and changes in liver enzymes in the pediatric population is limited. “A recent longitudinal study of 50-year-old adults reported that questionnaire-based self-reported vigorous PA but not moderate PA was associated with reduced risk of MASLD,” he writes. “However, studies on long-term patterns of accelerometer-based movement behaviours, such as ST, [LPA] and moderate-to-vigorous PA (MVPA), in relation to MASLD and liver fibrosis in the young population are lacking.”

For this study, Agbaje analyzed data from a long-term study of a large U.K. birth cohort, called the Avon Longitudinal Study of Parents and Children (ALSPAC) or the “Children of the ’90s —  2,684 children who had repeated measurements of their movements with a waist-worn accelerometer from ages 11 to 24 years. At ages 17 and 24, study participants underwent a liver ultrasound scan to assess for fatty liver and evidence of liver scarring. They also had bloodwork to measure their liver enzyme levels at those two timepoints.

On average, children from the study spent six hours a day sitting or otherwise being sedentary, but this time increased to nine hours daily by young adulthood, Agbaje found. In childhood, six hours per day was spent in light-intensity physical activity, which neutralized the deleterious effect of six hours per day spent sedentary.

For each half-hour of sedentary behavior above six hours per day, children had 15% higher odds of developing fatty liver disease before they were 25 years old. Any increase of sedentary time above six hours a day resulted in a corresponding decrease in the time spent in light-intensity physical activity, therefore three hours less daily by young adulthood. However, each additional half hour of light-intensity physical activity beyond 3 hours per day decreased the odds of severe fatty liver disease by 33%.

“We believe that this alteration in sedentary time versus time for light-intensity physical activity sets the stage for disease initiation and progression,” Agbaje says

The prevalence of MASLD was one in 40 participants at age 17 and one in five participants at age 24. Agbaje called this finding surprising because the risk of MASLD increased eightfold in only seven years and because a 20% prevalence of the disease would usually not occur until one’s mid-40s.

Half of the 24-year-olds with MASLD had severe disease, or a significantly high amount of excess fat in the liver. One in every 40 young adults already had signs of liver scarring, with three in 1,000 young adults meeting the diagnostic criteria for liver cirrhosis, Agbaje reported.

However, he found that engaging in light-intensity physical activity for at least three hours a day reversed this premature liver damage. Each cumulative minute of moderate-to-vigorous physical activity in a day was associated with a slightly lower likelihood of severe MASLD at age 24 but was not associated with a lower likelihood of liver cirrhosis.

“In conclusion,” Agbaje writes, “the prevalence of liver steatosis increased 8-fold during growth from adolescence (age 17 years) to young adulthood (age 24 years); however, increasing LPA and MVPA and decreasing ST may independently attenuate the risk of severe liver steatosis and liver cirrhosis in adolescence and young adulthood. Specifically, engaging in at least 3–4 h/day of LPA from childhood through young adulthood may protect 11 out of 1000 youths from the risk of liver cirrhosis and 4 out of 1000 youths from severe liver steatosis (SLD, MASLD and MASH). Similarly, engaging in at least 50 min/day of MVPA from childhood through young adulthood may protect 3 out of 1000 youths from premature severe liver steatosis (SLD, MASLD and MASH).”

Examples of light-intensity physical activity are outdoor games, playing at the playground, walking a dog, running errands for parents, or walking and biking.