The association between noncancer pain, cognitive impairment, and functional disability: An analysis of the Canadian study of health and aging

Background. Noncancer pain and cognitive impairment affect many older adults and each is associated with functional disability, but their combined impact has yet to be rigorously studied. Methods. This is a cross-sectional analysis of the Canadian Study of Health and Aging. Pain was collapsed from a 5-point to a dichotomous scale (no and very mild vs moderate and greater). Cognitive status was dichotomized from the Modified Mini-Mental State Examination (0-100) to no (>77) or mild-moderate (77-50) impairment. Five Instrumental Activities of Daily Living (IADL) and seven Activities of Daily Living (ADL) were self-rated as "accomplished without any help" (0), "with some help" (1), or "completely unable to do oneself" (2) and then summed to create a composite score of 0-10 and 0-14, respectively. Multivariate linear regression analysis was conducted to determine the associations between self-reported functional status with moderate or greater pain, cognitive impairment, and the interaction of the two. Results. A total of 5,143 (90.2%) participants were eligible, 1,813 (35.6%) reported pain at a moderate intensity or greater and 727 (14.3%) were cognitively impaired. The median IADL and ADL summary scores increased among the pain and cognition categories in the following order: no pain and cognitively intact (0.63 SD 1.24, 0.23 SD 0.80), pain and cognitively intact (1.18 SD 1.69, 0.57 SD 1.27), no pain and cognitively impaired (1.64 SD 2.22, 0.75 SD 1.57), and pain and cognitively impaired (2.27 SD 2.47, 1.35 SD 2.09), respectively. Multivariate linear regression found IADL summary scores were associated with pain, coefficient.17 (95% confidence interval [CI] 0.07-0.26), p <.01; cognitive impairment, coefficient.67 (95% CI 0.51-0.83), p <.01; and an interaction effect of pain with cognitive impairment, coefficient.24 (95% CI 0.01-0.49), p =.05. ADL summary scores were associated with pain coefficient.10 (95% CI 0.04-0.17), p <.01 and cognitive impairment, coefficient.29 (95% CI 0.19-0.39), p <.01, but had a nonsignificant interaction term, coefficient.12 (95% CI-0.03 to 0.29), p =.12. Conclusions. Noncancer pain and cognitive impairment are independently associated with IADL and ADL impairment and IADL impairment is even greater when both conditions are present.