Body weight, frailty, and chronic pain in older adults: a cross-sectional study

BACKGROUND: There exists limited data on the association between unhealthy body weight and chronic pain, and whether this association is explained by frailty status of older adults. METHODS: We included older adults aged ≥65 years from the 1999–2004 National Health and Nutrition Examination Survey (NHANES). Chronic pain was defined by self-reported pain lasting for ≥3 months in the past year. Body mass index (BMI) was categorized as underweight, normal, overweight, and obese. Participants were dichotomized as frail or non-frail based on a validated frailty index calculated as the proportion of the number of deficits present to a total of 45 possible deficits ascertained in NHANES. We used modified Poisson regression models to estimate prevalence ratios (PRs) and their 95% confidence intervals (CIs). RESULTS: Of 3693 older participants, one in six (15.9%) experienced chronic pain, with higher prevalence among the underweight (24.6%) and obese (20.2%) group. Frailty versus non-frailty was independently associated with BMI (PR = 1.25, 95% CI = 1.16–1.36 for underweight; and PR = 1.15, 95% CI = 1.07–1.22 for obese), and chronic pain (PR = 2.84, 95% CI = 2.18–3.69). After adjustment for frailty, the association between BMI and chronic pain decreased from PR = 1.82 to 1.64 for the underweight and 1.41 to 1.33 for the obese group. We did not observe an interaction effect between frailty and BMI. CONCLUSIONS: Unhealthy body weight was associated with increased chronic pain and the associations were partially explained by frailty status of older adults. Our findings generate hypotheses for further investigations of the interplay of these chronic conditions in older adults. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12877-019-1149-4) contains supplementary material, which is available to authorized users.