MONDAY, Dec. 17 (HealthDay News) -- The cost of lost productivity among U.S. workers with cancer is equal to 20 percent of the nation's health care spending, according to a new study.

Researchers analyzed national data from 2004 to 2008 and found that more than 3.3 million American workers are diagnosed with cancer each year. This results in more than 33 million disability days per year, translating to $7.5 billion in lost productivity.

Based on the average wages of workers included in the study, disability costs due to cancer were equal to 20 percent of total health care spending, according to the study, which was published in the December issue of the Journal of Occupational and Environmental Medicine.

Certain cancers, such as melanoma skin cancer and women's cancers, were associated with higher costs. For example, health care costs and hospitalizations were twice as high and disability days 55 percent higher for workers with breast cancer, compared to those with other cancers, according to a journal news release.

Nearly 85 percent of the workers with cancer were at companies with fewer than 500 employees. The workers at these companies also had higher rates of other health problems -- such as high blood pressure, depression and chronic obstructive pulmonary disease -- and were more likely to be uninsured than those at larger companies.

The true cost of lost productivity due to cancer is likely even higher than the disability days examined in this study, according to lead researcher Grant Skrepnek, of the University of Arizona Cancer Center, in Tucson, and colleagues.

They said more needs to be done to reduce the impact that cancer and its treatment has on productivity, such as supportive care programs to reduce cancer-related disability.

More information

The U.S. National Cancer Institute has more about the costs of cancer.