Background Due to large increases in the prevalence of obesity, there is a growing need to understand the relationship between obesity and rheumatoid arthritis (RA) outcomes. RA patients with high body mass index (BMI) have a greater of risk of disease persistence and higher disease activity scores compared to RA patients with lower BMI (1,2). This leads to higher levels of pain and disability, and can reduce quality of life (QoL) for RA patients in higher BMI groups. So far, most of the research looking at obesity in RA has focused on the QoL in terms of physical outcomes, but there has been relatively little investigation on the psychological impact on QoL amongst these patients.
Objectives To assess whether BMI at baseline predicts physical and mental health-related quality of life (HRQoL) for patients over three years in newly-diagnosed RA patients
Methods Data were from the Early Rheumatoid Arthritis Network (ERAN), a longitudinal observational study involving 21 rheumatology centres in the UK. Between 2002 and 2011 1,236 participants (397 male) were recruited. Sociodemographic and standard clinical variables were recorded at baseline, 6 months, 12 months and and then annually until loss to follow-up or the end of study follow up in 2013. QoL was measured using the Short Form 36 Health Survey Questionnaire (SF-36), a wide-ranging measure of health related QoL. Responses are grouped to form two higher-order constructs: Physical Component (PCS) and Mental Component (MCS). Linear regression models was estimated to determine if BMI as baseline was a predictor of the PCS and MCS scores at one year and 3 years, controlling for potential confounders
Results he analysis was restricted to 873 (71%) with data for both BMI and SF-36. Patients with complete data were younger (56.3 vs 58.7 years, p=.01) but did not differ in terms of gender (33% vs 30% male, p=.31), health assessment questionnaire disability (1.09 vs 1.07, p=0.68) or disease activity score (4.5 vs 4.5, p=0.88). Mean BMI at baseline was 27.6 kg/m2, increasing to 28.3 kg/m2 at 3 years – equivalent to a gain of 2.1 kg for an average height male (175cm), or 1.8 kg for an average height female (160cm). At baseline 66.6% of the sample fell into a WHO BMI category of overweight or obese. BMI at baseline associated with physical but nor mental QoL (bPCS=-0.2, p=0.003; bMCS=-0.04, p=0.58). After controlling for age, gender, baseline disease activity and baseline PCS and MCS score, BMI at baseline was a significant predictor of both physical and mental QoL at 3 years (bPCS=-0.5, p=0.001; bMCS=-0.3, p=0.004). Change in BMI between baseline and one year was not related to PCS or MCS at three years (bPCS=0.5, p=0.11; bMCS=0.2, p=0.58).
Conclusions Obesity is prevalent at the onset of disease in rheumatoid arthritis and, on average, patients gain weight over time. BMI at baseline is a predictor of poor long terms physical and mental QoL. Tailoring self-management interventions to account for obesity may help to improve long term outcomes.
de Rooy et al. Rheumatology, 2011:50(1),93–100
Heimans et al.Arthritis Care & Research, 2013:65(8),1235–1242
Disclosure of Interest None declared