Introduction Rates of sexually transmitted infections (STIs) among adults over 45 are rising in the UK and other Western countries. While STI rates are higher among men who have sex with men and young people, there is increased fluidity of sexual partnerships across the life course, exemplified by mid-life divorce and re-partnering, with sexual activity continuing beyond the age of 80. In order to develop a risk-reducing intervention for this age group, this qualitative study sought to understand the socio-cultural factors influencing late middle-aged adults’ knowledge of STIs.

Methods Recently sexually active heterosexual adults aged 45–65 (n=31) were recruited from a large city sexual health service and sport and leisure centres. In-depth individual interviews explored how STI-related knowledge was acquired across the life course. Interview data were transcribed and analysed thematically.

Results Most participants (n=19) lived in areas of high deprivation and most were divorced, separated or bereaved from partners (n=24). Two key themes revealed that STI-related knowledge was acquired over the life course through personal social circumstances and wider cultural influences: 1) early stigmatisation of STIs influenced current understandings and 2) women in particular learned about STIs through parenting their adolescent children. Further themes showed that 3) knowledge of STIs was stated tentatively and 4) current STI knowledge did not necessarily facilitate health-seeking behaviour.

Discussion Engagement with STI-related knowledge among middle-aged adults is influenced by socio-cultural factors including the enduring stigmatisation of STIs. Interventions tackling stigma should aim to recognise and legitimate changing sexual partnerships across the life course.