Sedentary childhood linked to premature liver damage, study finds

An increase in sedentary time from childhood caused premature liver damage, a new study shows. However, light physical activity could reverse the risk. The study was conducted in collaboration between the Universities of Bristol and Exeter, and the University of Eastern Finland, and the results were published in Nature's npj Gut and Liver.

For each half-hour of sedentary behavior above 6 hours per day, children had 15 percent increased risk of developing severe fatty liver disease as well as liver cirrhosis by 24 years of age. Sedentariness also significantly increased liver enzymes (alanine aminotransferase, aspartate aminotransaminase, and gamma-glutamyltransferase). However, each additional half hour of light physical activity (LPA) beyond 3 hours/day reduced the risk of severe fatty liver disease by thirty-three percent.

Excessive fat deposit in the liver and scarring of the liver also known as liver cirrhosis are signs of liver damage, which has been linked to increased risk of liver cancer and liver transplant. Elevated liver enzymes are early signs of liver inflammation, injury, and damage.

This is the largest and the longest follow-up accelerometer-measured movement behavior and liver scan study in the world in the pediatric and young adult population. The present study included 2684 children from the University of Bristol's Children of the 90s cohort who were followed up from age 11 until 24 years. At ages 17 and 24, study participants underwent a liver ultrasound scan (transient elastography) to assess for fatty liver and evidence of liver scarring. Blood samples were analyzed for liver enzyme levels at both time points.

The children's fasting blood samples were also repeatedly measured for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, glucose, insulin, and high-sensitivity C-reactive protein. Blood pressure, heart rate, smoking status, socio-economic status, family history of cardiovascular disease, as well as dual-energy X-ray absorptiometry measured fat mass and lean mass were accounted for in the analyses.

At baseline, children spent an average of six hours per day in sedentary activities, which increased to nine hours per day by young adulthood. In childhood, 6 hours per day was spent in LPA and any increase in sedentary time above 6 hours a day resulted in a corresponding decrease in the time spent in LPA, therefore 3 hours less daily by young adulthood.

Fatty liver disease is a harmful fat buildup in the liver. When the condition is not due to alcohol consumption but linked to at least one of five components of metabolic syndrome, it is called metabolic-associated steatotic (fatty) liver disease (MASLD). The prevalence of MASLD was 1 in 40 participants (2.5 percent) at age 17 and one in five participants (20 percent) at age 24.

It is rather surprising that the prevalence of MASLD increased eightfold in only seven years and because a 20 percent prevalence of the disease would usually not occur until one's mid-40s. The alteration in sedentary time versus time for LPA sets the stage for severe diseases such as premature liver, vascular, and cardiac organ damage as well as obesity, hyperinsulinemia, dyslipidemia, and worsening inflammation."

Andrew Agbaje, an award-winning physician and associate professor (docent) of clinical epidemiology and child health, University of Eastern Finland

"Half of the 24-year-olds with MASLD had severe disease, or a significantly high amount of excess liver fat. One in every 40 youths already had signs of liver scarring, with three in 1000 youths meeting the diagnostic criteria for liver cirrhosis. Liver damage is a silent killer disease that necessitates urgent public health surveillance in the young population" Agbaje continued.

Engaging in LPA for at least 3 hours a day neutralized this premature liver damage. Each cumulative minute of moderate-to-vigorous PA 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.

"The most effective antidote to the devastating health effects of childhood sedentariness is not the much-advertised moderate-to-vigorous PA of 60 minutes per day. Rather, it is the overlooked LPA of 3 to 4 hours per day. Examples of LPA are outdoor games, playing at the playground, walking a dog, running errands for parents, or walking and biking. We can encourage children and adolescents to participate in LPA daily for better liver health, thus defusing sedentariness ticking time bomb," Agbaje says.

Prof. Agbaje's research group (urFIT-child) is supported by research grants from Jenny and Antti Wihuri Foundation, the Finnish Cultural Foundation Central Fund, the Finnish Cultural Foundation North Savo Regional Fund, the Orion Research Foundation, the Aarne Koskelo Foundation, the Antti and Tyyne Soininen Foundation, the Paulo Foundation, the Yrjö Jahnsson Foundation, the Paavo Nurmi Foundation, the Finnish Foundation for Cardiovascular Research, Ida Montin Foundation, Eino Räsänen Fund, Matti and Vappu Maukonen Fund, Foundation for Pediatric Research, Alfred Kordelin Foundation, and the European Association for the Study of Obesity - Novo Nordisk Foundation New Investigator Award for Childhood Obesity.