Background/Purpose

Higher rates of obesity in psoriatic arthritis (PsA) compared to rheumatoid arthritis (RA) have been described. Obesity, C-reactive protein (CRP) and inflammatory arthritides itself are known risk factors for cardiovascular disease. Obesity is also shown to affect response to therapy in patients with inflammatory arthritis. This study aimed to compare BMI in RA, PsA and ax-SpA and additionally to examine for possible correlation between BMI and CRP in these diseases.

Methods

All the RA, PsA and ax-SpA patients that visited the out-patient clinic during the year 2013 were included. The RA patients had a diagnosis verified by the treating rheumatologist, the PsA patients all fulfilled the ClASsifcation for Psoriatic ARthritis (CASPAR) criteria and the ax-SpA patients all fulfilled the ASAS classification criteria for ax-SpA. BMI was calculated as the patient’s weight in kilograms divided by height in meters, squared. CRP was assessed by turbidimetry (mg/L). The unadjusted analyses of BMI and CRP were performed using analyses of variance (ANOVA) with post hoc tests (Tuckey HSD; homogeneity of variance). The adjusted analyses were performed by use of a General Linear Model with adjustments for age, sex, smoking, years of education, disease duration and multiple comparisons (Bonferroni). Correlation analysis of BMI and CRP was performed by use of Spearman’s rho.

Results

A total of 1045 RA, 351 PsA and 314 ax-SpA patients were included. Respectively, mean (SD) age was 62.9 (13.9), 55.2 (12.3), 48.2 (12.8) years, mean disease duration 12.5 (10.6), 9.9 (8.0), 13.2 (11.7) years, mean years of education 11.5 (3.6), 12.4 (3.6), 12.9 (3.5) years, percentages currently smoking 20.7, 18.6, 23.6 % and percentage females 68.0, 49.0 and 34.1%. In both unadjusted and adjusted analyses the PsA patients had significantly higher mean BMI compared to the RA and ax-SpA patients. The male PsA patients had significantly higher BMI than the RA and the ax-SpA patients in the unadjusted analyses, but this difference was only significant for the PsA patients compared to the RA patients in the adjusted analyses. For females the PsA patients had significantly higher BMI than the RA and the ax-SpA patients both in the unadjusted and in the adjusted analyses. There was only a significant correlation between BMI and CRP for females (rho=0.18, p<0.001).

	RA (n=1045)		PsA (n=351)		Ax-SpA (n=314)		p
Unadjusted analyses BMI (SE) (kg/m2)	25.9 (0.2)		27.7 (0.2)		26.4 (0.3)		<0.001a 0.259b 0.002c
	Males (n=334)	Females(n=711)	Males(n=179)	Females(n=172)	Males(n=207)	Females(n=107)	Males	Females
	26.8 (0.4)	25.5 (0.2)	28.1 (0.3)	27.2 (0.4)	26.8 (0.3)	25.7 (0.5)	0.023a 0.992b 0.034c	<0.001a 0.885b 0.018c
	RA (n=1045)		PsA (n=351)		Ax-SpA (n=314)		p
Adjusted analyses BMI (SE) (kg/m2)	25.9 (0.2)		27.4 (0.3)		26.1 (0.3)		<0.001a 1.000b 0.002c
	Males (n=334)	Females(n=711)	Males(n=179)	Females(n=172)	Males(n=207)	Females(n=107)	Males	Females
	26.7 (0.3)	25.5 (0.2)	28.1 (0.4)	27.1 (0.4)	27.1 (0.4)	25.6 (0.5)	0.037a 1.000b 0.194c	<0.001a 1.000b 0.031c

 

 

 a: RA – PsA, b: RA – ax-SpA, c:PsA – ax-SpA. 

Conclusion

In our population of patients with inflammatory arthritides, PsA patients were significantly more obese than RA and ax-SpA patients. These differences were more pronounced for female patients. A weak correlation between CRP and BMI was found, but only for females. Both CRP and obesity are independent cardiovascular risk factors. Given the increased risk of cardiovascular events in inflammatory arthritides, obesity represents a potentially important modifiable risk factor.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/norwegian-psoriatic-arthritis-patients-are-more-obese-than-rheumatoid-arthritis-and-axial-spondyloarthropathy-patients/