Work Ability and Employment in Rheumatoid Arthritis: A Cross-Sectional Study on the Role of Muscle Strength and Lower Extremity Function

Table 1

Characteristics of the study population and univariate comparison of subjects with and without gainful employment.

	Total population(n=100)			Gainfully employed subjects(n=59)			Non-gainfully employed subject (n=41)			p-value
Variable	N	Mean (SD)/Median [IQR]		N	Mean (SD)/Median [IQR]		N	Mean(SD)/Median[IQR]
Female gender	66		66	38		64	28		68.3	0.830
Age – years		53.0			49.0			58.0		<0.001
In a relationship	71		71	44		75	27		66	0.340
Education level										0.013
Compulsory	18		18	5		8	13		34
Secondary	71		71	46		78	25		61
Higher	11		11	8		14	3		7
Disease duration – months		78.00			60.0			78.0 (36.5-192)		0.260
Disease activity – CDAI		8.0 (8.2)			0.8 (7.9)			8.4 (8.8)		0.644
Pain - VAS		3.5 (2.05)			3.3 (1.9)			4.1 (2.2)		0.056
Inflammatory marker
CRP - mg/dl		3.2			2.6			3.9		0.035
IL-6 - pg/ml		3.9			3.7			4.1		0.443
TNF-alpha - µg/ml		1.6			1.3			1.9		0.273
Rheumatoid arthritis medication
sDMARDs	80		80	46		78	34		83	0.617
bDMARDs	44		44	30		50.8	14		34.1	0.107
Corticosteroids	17		17	10		16.9	7		17	1.000
NSAIDs/Pain killers	15		15	9		15.3	6		14.6	1.000
Comedication (non-RA)	55		55	25		42.4	30		73.2	0.001
Number of comedication		1			0			2		0.002
Comorbidities
Presence of comorbidity	65		65	32		54	33		81	0.007
Number of comorbidities		1			1			2.0		0.005
Functional Disability (HAQ - DI)		0.5			0.4			0.8		0.009
HAQ-DI ≤ 1, no disability	70		70	50			27			0.067
HAQ-DI >1, disability	28		28	9			12
Job demands
Predominantly physical	10		17
Predominantly mental	21		36
Mixed physical and mental	28		47
Workability index single item (WAS)		7.00			8.0			4		<0.001
Workability index (WAI)		37.3
Muscle strength - kg
Hand grip strength		29.4 (14.4)			32.1(14.9)			25.5 (12.9)		0.024
Knee extensor strength		36.4 (16.8)			41.5(17.1)			29.2 (13.6)		<0.001
Lower extremity function - (SPPB) total		10.8 (1.9)			11.3 (1.5)			10.1 (2.2)		0.003
Chair stands		3.2 (1.2)			3.6 (0.9)			2.7 (1.3)		0.010
Balance test		3.7 (0.7)			3.8 (0.6)			3.6 (0.9)		0.262
Walking test		3.9 (0.5)			3.9 (0.3)			3.8 (0.7)		0.030

SD=standard deviation, IQR=interquartile range, CDAI=clinical disease activity index, VAS=visual analogue scale, CRP=C-reactive protein, IL-6=interleukin-6, TNF-alpha=tumor necrosis factor-alpha, s/b DMARD=synthetic/biological disease-modifying antirheumatic drug, WAI=workability index, WAS=single item workability index, SPPB=short physical performance battery, and HAQ-DI=health assessment questionnaire-disability index.
Assessed for gainfully employed patients only.