Background Smoking is a proven risk factor for RA severity, and overweight has a negative impact on global health.
Objectives To compare the patient-reported disease burden in relation to smoking status and body weight in patients with rheumatoid arthritis (RA).
Methods The national database of the German collaborative arthritis centres collects clinical and patient-derived data from unselected outpatients with inflammatory rheumatic diseases. Patients with rheumatoid arthritis recorded in 2011 were grouped into non-smokers and ever smokers (past/active/social smoker), and by BMI (<30/ ≥30). Since these groups differed remarkably in age, sex and disease duration, we matched patients by sex and age as well as disease duration (in 2-years steps each). To avoid relying on 1 individual match only, for means and percentages of interest the average of 100 matching repetitions was calculated. Significance was assumed if the 95% confidence interval (CI) of the 100 group differences did not include the 0, for percentages we also required both CI-bounds of the group differences to be >=5% for any subcategory.
Results Overweight (n=958 pairs) was associated with poorer scores for functional capacity, pain, sleep and global health, while disease burden seemed to be independent of smoking (n=1,225 pairs). Combining both risk factors, matched patients were 62 years old and 89% female with mean disease duration of 8.4 years. The highest disease burden regarding functional capacity, global health, pain, fatigue and sleep disturbances was reported by obese smokers, not necessarily mirrored by parameters such as DAS28 or physician’s assessment (Tab.1). Interestingly, global disease activity assessed by the physicians on a numerical rating scale (NRS 0-10) showed group-specific differences from DAS28 results. The differences between the numbers of tender and swollen joints were highest in obese patients, and the highest ESR values were seen in obese current smokers (data not shown).
Conclusions While there were no differences between non-smokers and ever smokers, overweight patients showed a higher self-reported disease burden than normal weight patients, independent of age, sex and disease duration. Joint counts in overweight patients could be biased either by difficulties to determine swelling or by pain induced by other strains than RA. The detrimental influence of smoking and particularly obesity became apparent when both risk factors were combined. Counseling to both decrease overweight and to desist from smoking could help to improve patient reported outcomes in RA patients.
Acknowledgements The database was funded by the German Federal Minister of Research from 1999 to 2007 (grant #01 GI 0344/3). Since 2007, the Working Group of the regional corporate arthritis centers and a consortium of pharmaceutical companies has been funding the National Database by an unconditional grant to the German Rheumatological Society.
Disclosure of Interest None Declared