Aim: The broad aim of this thesis was to explore the impact pain has on frailty and its impact also on sexual health in middle age and older men and women. Background: Pain has been suggested to act as a stressor during aging, potentially accelerating declines in health and functioning. We hypothesised that pain, by acting as a potential stressor, may predispose to the development of, or worsening, frailty and may be associated also with poorer sexual health. Methods: Longitudinal and cross-sectional analyses were conducted within the population based European Male Ageing Study (EMAS) and the English Longitudinal Study of Ageing (ELSA) cohorts. Within EMAS, the presence of chronic widespread pain (CWP) was defined using the American College of Rheumatology criteria and within ELSA participants were asked whether they were âoften troubled with painâ and for those who reported yes, further information regarding the intensity of their pain (mild, moderate, or severe) was collected. In both cohorts, frailty was measured using a Frailty Index (FI). In ELSA, sexual health was measured using the Sexual Relations and Activities Questionnaire (SRA-Q). Analyses focused on the impact of pain on the occurrence of and worsening of frailty / sexual health. Results: In EMAS, among men who were non-frail at baseline, those with CWP were significantly more likely to develop frailty at follow up. After adjustment for age and centre, compared with those with no pain, those with CWP at baseline had a 70% higher FI at follow-up; these associations remained significant after further adjustment for smoking, body mass index, depression, physical activity and FI at baseline. These findings were supported by analysis conducted in men and women using ELSA and the associations persisted after further adjustment for either occupational class and/or net wealth level. There was no evidence that the association between pain and frailty was influenced by gender. Further, using data from ELSA the occurrence of pain did not, appear to result in an increased rate of developing frailty. The results of the sexual health analysis showed that, after age adjustment, compared to men experiencing no pain, men with moderate or severe pain reported less frequent intercourse and masturbation, more erectile difficulties, and more concerns about their sexual health and there were no associations between pain severity and sexual health among women. Cumulative pain scores were associated with concerns about sexual health in both men and women. Conclusions: Pain is associated with an increased risk and intensity of frailty in older men and women. Socioeconomic factors contribute to the occurrence of frailty; though do not explain the relationship between pain and frailty. Pain was associated with impairment in sexual health in men and women though the effect was more marked in men.