Study finds no link between sleep chronotype and liver disease markers

For years, researchers have suspected that night owls might be at higher risk for liver disease. The theory made intuitive sense: people whose bodies naturally run on a late schedule often find themselves fighting against the world's early-morning rhythms, disrupting sleep, meal timing, and metabolic balance in ways that could damage the liver. A team of Italian gastroenterologists decided to test this hypothesis directly.

They recruited 119 adults with overweight or obesity between February 2023 and July 2024, none of whom were taking medications that might affect their metabolism. The participants answered detailed questions about their natural sleep and activity preferences—whether they were morning people, evening people, or somewhere in between. Then the researchers used FibroScan, a non-invasive imaging tool, to measure two key markers of liver health: the amount of fat accumulating in the liver and the stiffness of liver tissue, which signals fibrosis, or scarring. Fibrosis matters because it indicates advanced disease and carries real prognostic weight; it can progress to cirrhosis and liver cancer.

The group they studied was metabolically troubled. Nearly all 119 participants were obese. Sixty-two percent already had liver fat accumulation. Fifteen percent showed signs of fibrosis. Many had undiagnosed type 2 diabetes. Their insulin resistance was marked. These were people at genuine risk for serious liver disease. If chronotype was going to matter, it should have shown up here.

It didn't. When the researchers analyzed the data, they found no meaningful correlation between a person's chronotype—their natural preference for morning or evening activity—and either the amount of liver fat or the degree of liver stiffness. They tested this relationship multiple ways: as a continuous measure, as categorical groupings, and with statistical adjustments for sex, age, body mass index, waist circumference, and insulin resistance. The answer remained the same. Evening types did not have worse liver markers than morning types.

What did correlate strongly with liver damage was what you might expect: obesity itself, insulin resistance, and metabolic dysfunction. Liver fat tracked closely with body weight, waist circumference, and blood sugar control. Liver stiffness correlated with adiposity and insulin resistance. The liver, in other words, was responding to metabolic strain, not to the timing of someone's circadian rhythm.

The researchers were careful not to overclaim. Their study was small, and the confidence intervals left room for the possibility of small-to-moderate effects, particularly for fibrosis, that a larger study might detect. But as it stands, the data offer no evidence that chronotype—the internal clock that makes you a morning person or a night owl—is a meaningful driver of liver disease in people with obesity. The damage appears to come from metabolic dysfunction itself, not from the mismatch between your body's preferred schedule and the world's demands.

This finding complicates a growing body of research suggesting that evening chronotype contributes to worse metabolic and cardiovascular outcomes. It also raises a question for future work: if circadian misalignment harms metabolic health in other ways, why not the liver? The answer may require larger, longer studies that follow people over time rather than taking a single snapshot. For now, the Italian team has documented one negative result—and in science, knowing what doesn't matter can be as useful as knowing what does.