In 2002 he was made an Associate Professor in Gerontology. He has almost thirty years of experience working as a Senior Research Associate, specializing in housing, services and the care of elderly people. His main fields of interest are informal caregiving and the social policy of eldercare. In 1993 Lennarth joined the National Board of Health and Welfare as a research leader with responsibility for the evaluation of eldercare reforms. During recent years he has also been involved in several international comparative studies on the care of elderly people. Since the start of 2010 he has divided his time between the National Board of Health and Welfare and the Aging Research Center where he is a senior researcher in the social gerontology group.