Erdman Palmore is a professor emeritus of medical sociology at the Duke Center for the Study of Aging at Duke University Medical Center.

He has written or edited 15 books on social aspects of aging, life satisfaction, longevity, ageism and international gerontology, including “The Encyclopedia of Ageism,” a comprehensive review of more than 125 aspects of ageism.

He talked to Growing Bolder about the third great “-ism.” He said he spent his younger years fighting racism and sexism, but the nation is still discriminating against people just because of their age.