Background Patients with long standing rheumatoid arthritis (RA) are more prone to develop rheumatoid cachexia which is associated with increased morbidity and premature mortality. Over the last decades improved RA treatment has resulted in reduced inflammation, and patients report better physical function. Being underweight or obese may be associated with worse physical function and higher disease activity in established RA, but the underlying mechanisms are unclear.
Objectives To examine whether patient reported outcomes (PRO) differ between underweight (UW), normal weight (NW) overweight (OW) and obese (OB) RA patients during 5 cross-sectional examination points over 15 years.
Methods Mailed surveys were sent to all patients in the Oslo RA registry (ORAR) in 1994/1996/2001/ 2004/2009. ORAR is representative for RA patients in Oslo aged 20-79 years. Response rates were 931(74.5%)/ 1025(74.5%)/ 893(58.5)/ 914(62.9%)/ 986(59.7%) respectively, with a 3:1 female: male ratio. The questionnaires included the modified health assessment questionnaire (MHAQ), SF-36 (also used to compute SF6D), visual analogue scales for pain, fatigue and global disease activity, height and weight. Body mass index (BMI) <18.5 indicates UW, BMI 18.5-24.9 NW, BMI 25.0-29.9 OW and BMI ³30.0 OB. Results are presented as means with standard deviation (SD) or 95% confidence intervals (CI).
Results Mean (SD) BMI in the RA population increased from 23.3(4.8) in 1994 to 25.1(4.6) in 2009. UW decreased from 6.3% to 3.7%, while OB increased from 5.1% to13.6% over the 15 years. Pain and disease activity levels were similar across BMI subgroups, with a trend towards higher values for UW and OB at all examination points with overlapping 95% CI. UW patients reported the worst physical function and lowest utility scores, and had highest age and longest disease duration. Age and disease duration for the entire population were not statistically different between examination points. NW were the youngest and had the highest utility SF6D score. OB had the shortest disease duration and MHAQ only improved from 04-09. SF-36 PCS scores mimicked MHAQ scores but OB were worse than UW. Pain and fatigue VAS scores were highest for UW and OB, data not included. NW and OW scored almost identical on all measures (data not included).
Conclusions Even though the proportion of UW RA patients decreased during the observation period and they reported improved utility, physical function and global disease activity, they never caught up with the improvement seen in NW and OW RA patients. The increasing proportion of OB patients is a worrying trend, especially when considering the additional burden of other health problems.
Disclosure of Interest None Declared