Dementia patients don’t often get the flu. But when they do it tends to be more deadly than in patients without dementia, according to a new study.

The Tufts University study examined five years of Medicare and Medicaid records. It found that of the 36 million seniors hospitalized between 1998 and 2002, 6 million were diagnosed with flu or pneumonia. Of those, roughly 800,000—or 13%—also had dementia. Despite this low number, dementia patients are 50% more likely to die from flu or pneumonia than non-dementia patients, according to researchers.

Dementia patients may have difficulty communicating flu symptoms to caregivers, researchers suggest. They also say that limited access to healthcare and inadequate testing practices could contribute to the higher mortality rates among dementia patients. The report was published online on Oct. 26 in the Journal of the American Geriatrics Society.