In a new study, investigators analyzed data on more than 1,300 US patients, aged 66 and older, who had one of three types of major surgery (abdominal aortic aneurysm repair, coronary artery bypass graft, or colectomy) between 1992 and 2014.

Before their surgery, at least 90% of the patients were independent or did not need help with activities of daily living or instrumental activities of daily living, 6% had dementia, 23% had thinking ("cognitive") impairment without dementia, and 25% had depression.

Activities of daily living include bathing, dressing, eating, using the bathroom, getting in and out of bed, and walking across the room. Instrumental activities of daily living include preparing meals, handling finances, using the phone, shopping and taking medication.

Overall, 17% of the patients died within a year after their surgery, the findings showed.

Rates of death were 29% among those who needed support for at least two activities of daily living vs 13% among those who were independent.

The risk of death rose as the number of risk factors increased: 10% for no factors, 16% for one factor and nearly 28% for two factors, according to the study published March 11 in JAMA Surgery.

These findings show the need for research into how to incorporate these risk factors into pre-surgery assessments of seniors, said study lead author Dr. Victoria Tang. She is an assistant professor of geriatrics and of hospital medicine at the University of California, San Francisco, and the affiliated San Francisco VA Health Care System.

"Improving our understanding of functional, cognitive, and psychological risk factors in this population, particularly in predicting risk beyond typical medical factors, is essential to providing patient-centered care," Tang concluded in a university news release.