Physical activity and sedentary behavior in patients with systemic lupus erythematosus and rheumatoid arthritis

Figures & data

Table 1 Baseline characteristics of the study participants at enrollment (N = 59)a–c

Variables	SLE (N = 20)	RA (N = 19)	Control (N = 20)	p-value
Demographic information
Female, n (%)	18 (90.0%)	11 (57.9%)	13 (65.0%)	0.065
Age, years, mean (SD)	43.9 (12.5)	51.5 (13.4)	50.9 (11.2)	0.106
Caucasian race, n (%)	17 (85.0%)	17 (89.5%)	20 (100%)	0.217
Marital status, n (%)				0.764
Single/divorced/separated	6 (30.0%)	5 (26.3%)	4 (20.0%)
Married/common-law	14 (70.0%)	14 (73.7%)	16 (80.0%)
Education, years, mean (SD)	15.1 (3.1)	15.1 (2.3)	18.6 (3.5)	0.001
BMI, kg/m^2, mean (SD)	28.1 (5.9)	27.3 (7.7)	25.3 (4.4)	0.349
Household income (CAD), n (%)				0.011
<$75,000/year	10 (58.8%)	12 (63.2%)	4 (20.0%)
>$75,000/year	7 (41.2%)	7 (36.8%)	16 (80.0%)
Missing	3
Health behaviors
Cigarette smoking, n (%)	3 (15.0%)	7 (36.8%)	2 (10.0%)	0.088
Alcohol use, n (%)	9 (47.4%)	11 (57.9%)	14 (70.0%)	0.356
Comorbidities
Diabetes, n (%)	1 (5.0%)	1 (5.3%)	0 (0%)	0.588
Hypertension, n (%)	8 (40.0%)	2 (10.5%)	0 (0%)	0.002
Dyslipidemia, n (%)	4 (20.0%)	2 (10.5%)	1 (5.0%)	0.333
Depression, n (%)	6 (30.0%)	1 (5.3%)	2 (10.0%)	0.072
Chronic pain, n (%)	7 (35.0%)	6 (31.6%)	5 (25.0%)	0.784
Measures of function and disability
HAQ score, mean (SD)	0.06 (0.17)	0.35 (0.55)	0 (0)	<0.001
SF-36, mean (SD)
PCS	37.7 (10.8)	45.6 (9.0)	55.4 (3.9)	<0.001
MCS	46.5 (10.9)	49.5 (11.4)	53.7 (8.8)	0.059

Notes:

a All comparisons for categorical variables were performed using chi-square test (df = 2).

b Age, years of education, and SF-36 PCS scores were normally distributed and were compared using one-way ANOVA.

c BMI, HAQ scores, and SF-36 MCS scores were not normally distributed and were compared between groups using Kruskal–Wallis test. Bold indicates statistically significant results after Bonferroni adjustment for multiple comparisons (p≤0.001).

Abbreviations: BMI, body mass index; HAQ, Health Assessment Questionnaire; MCS, Mental Component Summary; PCS, physical component summary; RA, rheumatoid arthritis; SF-36, Short Form-36; SLE, systemic lupus erythematosus.

Table 2 Disease characteristics and laboratory data of SLE and RA patients

	SLE patients (N = 20)	RA patients (N = 19)
Disease characteristics
Disease duration, years, mean (SD)	14.1 (10.1)	14.6 (10.6)
Medications
Prednisone, n (%)	3 (15.0)	1 (5.3)
DMARDs, n (%)	12 (60.0)	17 (89.5)
Antimalarials, n (%)	13 (65.0)	6 (31.6)
Biologics, n (%)	0 (0)	11 (57.9)
Blood pressure, mmHg, mean (SD)
Systolic	124.4 (21.7)	120.4 (11.3)
Diastolic	73.8 (14.4)	72.3 (8.7)
TJC, mean (SD)		2.42 (7.07)
SJC, mean (SD)		2.68 (4.06)
DAS28-ESR, mean (SD)		2.76 (1.35)
DAS28-CRP, mean (SD)		2.27 (1.42)
ACR criteria at diagnosis, mean (SD)	6.1 (1.3)
SLEDAI-2K, mean (SD)	2.9 (2.1)
SDI, mean (SD)	1.75 (2.3)
Laboratory investigations
CRP, mg/L, mean (SD)	4.00 (4.4)	6.49 (10.2)
ESR, mm/hr, mean (SD)	44.9 (38.7)	17.6 (16.6)
RF positive, n (%)		14 (73.7)
Anti-CCP positive, n (%)		16 (84.2)
Fasting glucose, mmol/L, mean (SD)	5.2 (1.4)	4.9 (1.1)
Lipid profile, mean (SD)
Triglycerides, mmol/L	1.12 (0.51)	0.86 (0.47)
LDL cholesterol, mmol/L	2.27 (0.76)	2.70 (0.93)

Abbreviations: ACR, American College of Rheumatology; anti-CCP, anti-cyclic citrullinated peptide; CRP, C-reactive protein; DAS28, Disease Activity Score-28; DMARDs, disease-modifying antirheumatic drugs; ESR, erythrocyte sedimentation rate; LDL, low-density lipoprotein; RA, rheumatoid arthritis; RF, rheumatoid factor; SDI, SLICC/ACR Damage Index; SJC, swollen joint count; SLE, systemic lupus erythematosus; SLEDAI-2K, SLE Disease Activity Index 2000; SLICC, Systemic Lupus International Collaborating Clinics; TJC, tender joint count.

Table 3 Habitual sedentary time, light activity, and MVPA for SLE, RA, and healthy participants measured using accelerometry and by self-report using the PA Indexa

	SLE (N = 20)	RA (N = 19)	Healthy (N = 20)	p-value
Accelerometry data
Sedentary minutes/day, mean (SD)	603.6 (68.7)	603.4 (72.5)	618.0 (93.5)	0.800
Light activity minutes/day, mean (SD)	127.0 (37.2)	150.5 (48.5)	140.7 (28.5)	0.172
Total MVPA minutes/day, mean (SD)	34.5 (22.7)	41.5 (21.3)	64.9 (22.4)	<0.001 (0.003)b
Guidelines met, n (%) (≥150 minutes MVPA bouts/week)	2 (10.0)	3 (15.8)	9 (45.0)	0.028c
Self-report data from the PA Index Questionnaire
Sedentary minutes/day, mean (SD)	387.0 (233.2)	416.8 (233.6)	468.0 (221.6)	0.533
Light activity minutes/day, mean (SD)	262.5 (171.1)	347.4 (133.5)	268.5 (184.5)	0.212
Total MVPA minutes/day, mean (SD)	198.0 (214.2)	192.6 (177.3)	249.0 (208.1)	0.625

Notes:

a All continuous variables were normally distributed. Comparisons between groups for continuous variables were made using ANOVA.

b For total MVPA minutes/day, comparison between groups was also made using ANCOVA with HAQ scores, years of education, and SF-36 PCS scores as covariates, p-value is given in parentheses.

c Comparisons for categorical variables made using Fisher’s exact test.

Abbreviations: ANCOVA, analysis of covariance; HAQ, Health Assessment Questionnaire; MVPA, moderate–vigorous physical activity; PA, physical activity; PCS, physical component summary; RA, rheumatoid arthritis; SF-36, Short Form-36; SLE, systemic lupus erythematosus.

Table 4 Comparison of mean daily sedentary time, light activity, and MVPA measured using accelerometry and by self-report using the PA Index for SLE, RA, and healthy control study participants

	Accelerometry	PA Index Questionnaire	Difference in means (SD)a	p-valueb
SLE (N = 20)
Sedentary minutes/day, mean (SD)	603.6 (68.7)	387.0 (233.2)	216.6 (248.3)	0.001
Light activity minutes/day, mean (SD)	127.0 (37.2)	262.5 (171.1)	−135.5 (172.2)	0.002
Total MVPA minutes/day, mean (SD)	34.5 (22.7)	198.0 (214.2)	−163.5 (207.5)	0.002
RA (N = 19)
Sedentary minutes/day, mean (SD)	603.4 (72.5)	416.8 (233.6)	186.6 (198.3)	0.001
Light activity minutes/day, mean (SD)	150.5 (48.5)	347.4 (133.5)	−196.9 (131.0)	<0.001
Total MVPA minutes/day, mean (SD)	41.5 (21.3)	192.6 (177.3)	−151.2 (169.4)	0.001
Healthy control participants (N = 20)
Sedentary minutes/day, mean (SD)	618.0 (93.5)	468.0 (221.6)	150.0 (237.1)	0.011
Light activity minutes/day, mean (SD)	140.7 (28.5)	268.5 (184.5)	−127.8 (190.1)	0.007
Total MVPA minutes/day, mean (SD)	64.9 (22.4)	249.0 (208.1)	−184.1 (215.0)	0.001

Notes:

a Difference calculated as the accelerometry estimate minus the self-report questionnaire estimate.

b p-value for the paired t-test comparing means between the two PA measurement methods.

Abbreviations: MVPA, moderate–vigorous physical activity; PA, physical activity; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus.