(Bloomberg) Difficulty in reading and understanding medical information may raise the risk of death in older people, researchers said today.

Patients aged 65 and older who got low scores on a "health literacy" test were more likely to die over a five-year period than people with a better grasp of medical terminology and advice, said doctors led by David Baker of the Northwestern University School of Medicine in Chicago, in a study.

Patients who can't understand health advice, drug dosing instructions, or other medical information are at risk of harm or neglect, Baker and his colleagues said in the study published today in the Archives of Internal Medicine.

"Inadequate health literacy is associated with less knowledge of chronic disease and worse self-management skills for patients with hypertension, diabetes mellitus, asthma and heart failure," the authors concluded.

"Use of cancer screening and vaccinations are also lower among people with inadequate health literacy."

A 1997 survey of 3,260 patients enrolled in Medicare, the US health programme for the elderly and disabled, found that one in four scored poorly on tests of comprehension of medical reading and maths problems. About 39 percent of those patients died over the next five years, compared with 19 percent of patients with adequate health literacy, the study said.

The difference in heart disease risk was most pronounced among the groups.

While just 7.9 percent of health-literate patients died of heart disease, the No. 1 killer in the US, 19.3 percent of patients with inadequate health literacy died of cardiac illnesses, the study said.