A new study confirms long-standing suspicions: Rates of advanced liver disease (ALD) are increasing substantially in baby boomers living with hepatitis C virus (HCV), likely because many have not been tested or treated for the disease. The sobering findings were highlighted by Martin Zalesak, MD, PhD, from Trinity Partners in Waltham, Massachusetts, and his colleagues at the Digestive Disease Week 2012 conference in San Diego and reported by Medscape.

If undiagnosed and untreated, hep C can result in ALD, which encompasses a range of serious liver problems such as cirrhosis, decompensated (unstable and life-threatening) cirrhosis, liver cancer and liver transplants.

Of the estimated 3.6 million Americans who had hepatitis C in 2008, 1.6 million remained undiagnosed—and without a diagnosis, they can’t receive treatment, allowing liver disease to progress unchecked.

According to Zalesak’s calculations, the incidence of ALD is expected to climb from almost 200,000 new cases in 2008 to just over 300,000 new cases in 2015.

For the study, researchers analyzed insurance claims data from Medicare and from PharMetrics (a private provider of claims data). The numbers revealed trends in ALD progression and mortality, which the researchers used to extrapolate ALD prevalence in 2015, assuming a lack of treatment—a reasonable assumption for the many HCV-positive people unaware of their status.

Of the 1.1 million Americans who had a diagnosed HCV infection in 2008, the researchers found that 16.1 percent were 16 to 44 years old, 38.8 percent were 45 to 54, 36.4 percent were 55 to 64, and 8.6 percent were 65 and older.

Among those with hep C, the older they were, the more likely they were to be diagnosed with ALD. Specifically, 9.1 percent of those ages 16 to 44 were expected to be diagnosed with ALD by 2015. This climbed to 17.1 percent among ages 45 to 54, then to 22.4 percent for ages 55 to 64 years, and 19.3 percent among ages 65 and older.

“This alarming finding places additional stress on an already overburdened health care system, which will need to prepare for an increase in patients suffering from advanced liver disease,” said study coauthor Ann Kwong, PhD, vice president and HCV franchise lead at Vertex Pharmaceuticals.