Researchers have discovered that your geographic location and exposure to sunlight may influence liver cancer risk through a mechanism called solar jet lag, a type of circadian disruption that occurs when your internal clock falls out of sync with the sun's natural rhythm. A Fred Hutch Cancer Center epidemiologist recently received a nearly $1 million grant from the American Cancer Society to investigate this unexpected connection, marking the first-ever large-scale study of solar jet lag and hepatocellular carcinoma (HCC), the most common form of liver cancer .

What Is Solar Jet Lag and How Does It Affect Your Liver?

Solar jet lag sounds like something that happens when you travel across time zones, but it's actually caused by where you live. The term describes a specific type of circadian misalignment that occurs when your body's internal clock doesn't match the timing of sunrise and sunset in your geographic location. People living in the western part of a time zone experience later sunrises and sunsets, which can delay their internal clock, suppress melatonin production, and reduce sleep quality and duration .

This chronic mismatch between your body's clock and the sun's clock creates a persistent source of circadian disruption similar to what shift workers experience. The liver plays a central role in regulating your body's circadian rhythms, with approximately 10% of the liver's genes showing rhythmic expression, particularly those involved in metabolism. When this rhythm is disrupted, it can trigger a cascade of metabolic problems .

"The circadian clock plays a central role in the regulation of liver function and approximately 10% of the liver transcriptome is rhythmically expressed, including genes involved in metabolism," explained Trang VoPham, PhD, MPH, MS, epidemiologist at Fred Hutch Cancer Center.

Trang VoPham, PhD, MPH, MS, Associate Professor, Fred Hutch Cancer Center

How Could Solar Jet Lag Lead to Liver Cancer?

The connection between solar jet lag and liver cancer risk appears to work through several metabolic pathways. Circadian disruption may promote obesity, diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD, formerly called non-alcoholic fatty liver disease), which is now the fastest-growing known cause of HCC. The disruption affects glucose metabolism and bile acid synthesis, creating conditions that can eventually lead to liver cancer .

Currently, the major known risk factors for HCC include cirrhosis, chronic hepatitis B and C infections, heavy alcohol consumption, MASLD, obesity, and diabetes. However, this emerging research suggests that geographic location and the resulting circadian misalignment may be an additional modifiable risk factor that has been largely overlooked .

Who Is Most Vulnerable to This Risk?

Preliminary research has revealed important disparities in how solar jet lag may affect liver cancer risk. VoPham and her team found that the association between solar jet lag and HCC risk was stronger among Asian, Pacific Islander, and Alaska Native/American Indian people compared to non-Hispanic White individuals. This finding is particularly significant because HCC already shows marked disparities, with higher risk among men than women and among Alaska Native, American Indian, and Hispanic populations than other racial or ethnic groups .

The reasons for these disparities are not fully understood, though differences in access to healthcare and prevalence of other HCC risk factors explain some, but not all, of the observed variation. VoPham believes solar jet lag may play a role in these health inequities.

How Will Researchers Study This Connection?

The new research will pair a high-resolution geospatial light exposure model that calculates solar jet lag scores with electronic health records from the Veterans Health Administration, the largest integrated healthcare system in the United States. The team will examine data from 23 million Veterans Affairs patients, including more than 60,000 HCC cases diagnosed between 2001 and 2024 .

This large-scale approach will allow researchers to determine whether higher solar jet lag exposure correlates with increased HCC risk and whether this relationship varies by race, ethnicity, and other demographic factors. The study represents a significant shift in how scientists think about liver cancer prevention, moving beyond traditional risk factors to consider environmental and geographic influences on circadian health.

Steps to Protect Your Liver Health

While research on solar jet lag continues, experts emphasize that protecting your liver requires attention to established risk factors and lifestyle choices. Here are evidence-based approaches to support liver function:

• Get Screened for Hepatitis C: Hepatitis C is called the "silent killer" because people can live without symptoms for years while the virus damages their liver. All adults 18 and older should be tested at least once, and pregnant people should be screened during each pregnancy. Early detection allows treatment with oral antiviral medications that cure 95% to 99% of cases .
• Limit Alcohol Consumption: Drinking alcohol accelerates liver scarring and can hasten the progression to cirrhosis, particularly in people with existing liver disease. Avoiding or minimizing alcohol intake is one of the most important protective measures .
• Maintain a Healthy Weight and Diet: Obesity and metabolic dysfunction contribute to MASLD, the fastest-growing cause of liver cancer. A balanced diet and regular aerobic physical activity help maintain a healthy body mass index and reduce liver fat accumulation .
• Get Regular Liver Function Tests: About 30% of people with inflammatory bowel disease have abnormal liver test results at some point, often without symptoms. Routine blood tests measuring liver enzymes like ALT (alanine transaminase) and AST (aspartate transaminase) can detect problems early, when treatment is most effective .
• Be Cautious With Medications: Certain medications used to treat inflammatory bowel disease, including thiopurines like azathioprine, can cause liver toxicity in about 13% of users. Regular liver monitoring is recommended when taking these medications .

What Should You Know About Hepatitis C Treatment?

If you're diagnosed with hepatitis C, treatment has become remarkably effective and straightforward. The most commonly prescribed medications are Epclusa (sofosbuvir and velpatsvir) and Mavyret (glecaprevir and pibrentasvir), both taken as pills. These treatments are well-tolerated in more than 95% of patients, with side effects typically limited to headache and tiredness .

"Hepatitis C is a bloodborne virus that can lead to liver inflammation and scarring. In the United States, it's primarily transmitted through sharing needles during intravenous drug use, sniffing drugs and through non-sterile tattooing practice," noted Khalid Mumtaz, MBBS, MSc, Director of Hepatology at Ohio State Wexner Medical Center.

Khalid Mumtaz, MBBS, MSc, Director of Hepatology, Ohio State Wexner Medical Center

Treatment duration depends on the degree of liver scarring, lasting either three or six months. Within six months of infection, about 15% to 20% of people naturally clear the virus through their immune system, but the remaining 80% to 85% develop chronic hepatitis C that requires treatment. Left untreated, the virus can cause cirrhosis within 10 to 20 years, potentially leading to liver failure or liver cancer .

Why Early Detection Matters for Liver Health

The five-year survival rate for HCC is only 22%, and it drops dramatically when the cancer is diagnosed at later stages. When liver cancer spreads to distant sites, the five-year survival rate falls to just 3%. This stark reality underscores why identifying risk factors and screening for conditions like hepatitis C is so critical .

The liver performs more than 500 vital functions, including detoxification, bile production, nutrient storage, blood filtration, and regulation of metabolism and blood clotting. Protecting this essential organ through screening, lifestyle modifications, and early treatment of infections can prevent serious disease and potentially save your life. As research continues to uncover unexpected risk factors like solar jet lag, a comprehensive approach to liver health that addresses both traditional and emerging factors becomes increasingly important.