Objectives Retirement constitutes a major life transition that poses significant challenges to health, with many retirees experiencing a precipitous decline in health status following retirement. We examine the extent to which membership in social groups following retirement determines quality of life and mortality.

Design The longitudinal impact of the number of social group memberships before and after the transition to retirement was assessed on retirees’ quality of life and risk of death 6 years later.

Setting Nationally representative cohort study of older adults living in England.

Participants Adults who underwent the transition to retirement (N=424). A matched control group (N=424) of participants who had comparable demographic and health characteristics at baseline but did not undergo the transition to retirement were also examined.

Outcome measures Analyses examined participants’ quality of life and mortality during a period of 6 years.

Results Retirees who had two group memberships prior to retirement had a 2% risk of death in the first 6 years of retirement if they maintained membership in two groups, a 5% risk if they lost one group and a 12% risk if they lost both groups. Furthermore, for every group membership that participants lost in the year following retirement, their experienced quality of life 6 years later was approximately 10% lower. These relationships are robust when controlling for key sociodemographic variables (age, gender, relationship status and socioeconomic status prior to retirement). A comparison with a matched control group confirmed that these effects were specific to those undergoing the transition to retirement. The effect of social group memberships on mortality was comparable to that of physical exercise.

Conclusions Theoretical implications for our understanding of the determinants of retiree quality of life and health, and practical implications for the support of people transitioning from a life of work to retirement are discussed.