Background OA is the most common joint condition, the fourth leading cause of disability globally and the fastest increasing major health condition. In older adults, OA frequently coexists with other morbidities, but the temporal nature is unclear. There is abundant evidence that markers of low SES are associated with poor outcomes among people with musculoskeletal conditions, however the mechanism linking comorbidity may vary with SES.
Objectives To examine if OA predicted the onset of comorbidities that are the reason for frequent consultation to primary care, and if this association was moderated by SES.
Methods Cohort study combining questionnaire data at two time points (2005, 2008) in the North Staffordshire Osteoarthritis Project, and medical record data from 2000 to 2005 (n=3910). OA was defined by consultation to primary care for OA between 2000 and 2005, and the indication of moderate to extreme pain interference in the questionnaire (2005). Logistic regression examined the association between OA and the onset of seven comorbidities (anxiety, depression, widespread pain (WP), insomnia, cognitive impairment, neurosis, stress between 2005 and 2008) and restricted social participation, first unadjusted and then adjusting for putative confounders (comorbidity, socio-demographic and lifestyle factors). Moderation of the association between OA and new onset comorbidity by change in income, education and area-level deprivation was examined by including interaction terms in regression and stratified analyses. Results were reported as odds ratios with a 95% Confidence Interval (OR; 95% CI).
Results Mean age was 63, 55% were female, and 942 (24%) had OA. In the unadjusted analysis, OA was significantly associated with new onset of seven comorbidities (p<0.05). After adjusting for confounders, OA was associated with the onset of WP (2.49; 1.96–3.17) and insomnia (1.58;1.14–2.19) There was a significant non-multiplicative interaction between OA and income and new onset cognitive impairment (P=0.047); new onset of cognitive impairment in those with OA whose income remains adequate 29.1% cf 38.1% in those with OA whose income remains inadequate), and between OA and education and new onset WP (P=0.012; new onset in those with OA and secondary education only was 37.4% cf 50% in those with OA and had more than a secondary education).
Conclusions Consulters for OA were more likely to develop new physical and psychological comorbidities that lead to more frequent consultation to primary care than those without OA. Whilst confounders explained some of these associations, OA consulters may benefit from more proactive strategies to prevent further morbidity. Despite no significant multiplicative interactions, there were differences in the prevalence of new onset of morbidity in those with OA when stratified by SES. Onset of cognitive impairment was associated with inadequate income but WP was associated with those with higher education suggesting a “worried well” population seen both in other health surveys and in screening. OA and baseline morbidities were higher with lower SES and further exploration across the life- course will help to establish the role of SES on the natural history OA.
Disclosure of Interest None declared
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