Jacqui Smith of the University of Michigan Institute for Social Research along with Anna Kleinspehn-Ammerlahn and Dana Kotter-Gruehn at the Max Planck Institute for Human Development in Berlin analyzed the responses of 516 men and women 70 and older who participated in the Berlin Aging Study. They tracked how their perceptions about age and their satisfaction with aging changed over a six-year period.

"We examined individual changes over time, and expected the gap to increase. But we were surprised to find that it was maintained, on average. Perhaps feeling about 13 years younger is an optimal illusion in old age," Smith said in a statement. Smith and colleagues found that some of the oldest participants did feel even younger over time, but poor health reduced the gap between felt age and actual age.

In general, at the start of the study people said they looked about 10 years younger than they were, but by the end of the study, people felt they looked about seven years younger than their chronological age.

"Women saw themselves as about four years older than their male peers," Smith said in a statement. "Women may be more aware of their appearance than men, especially given the negative stereotypes of older bodies."

The findings are published in the Journals of Gerontology.