Older adults aren’t able to accurately predict their true life expectancy, which could affect the decisions they make about future health interventions, according to a new study out of the University of California, San Francisco, and the San Francisco Veterans Affairs Medical Center. The results were published in an Oct. 19 research letter in JAMA Internal Medicine.

“We thought older people would have a good sense of how long they had to live and have better estimates than a prognostic calculator that is based on things like age, gender and chronic diseases,” said lead author Rafael Romo, PhD, RN, a doctoral graduate in the UCSF School of Nursing and VA Quality Scholars Nurse Fellow at the San Francisco VA Medical Center. “But we were wrong. It turns out that older people are not very good at predicting their prognosis compared to either their actual survival or a calculated estimate. Further, the older you are, the worse you are at predicting.”

Older adults who underestimate their survival may choose to forego interventions likely to help them, the researchers write, whereas those who overestimate may choose interventions more likely to harm them.

The researchers found that underestimation of life expectancy was relatively similar across age groups, but overestimation increased significantly with age. Further, participants aged 64 and 69 years were moderately able to estimate survival, but older participants were no better than chance alone.

“We were surprised to find that people tended to underestimate how long they have to live—not overestimate—compared to the clinical estimates,” Romo said. “This goes against common wisdom that says older people are more likely to overestimate.”