Physical activity and body composition in patients with ankylosing spondylitis.
OBJECTIVE
Patients with ankylosing spondylitis (AS) are at risk for accelerated muscle loss and reduced physical activity. Accurate data are needed on body composition and physical activity in this patient group. The purpose of this study was to investigate body composition and objectively assessed physical activity in patients with AS.


METHODS
Twenty-five AS patients (15 men, mean ± SD age 48 ± 11 years) were compared with 25 healthy adults matched for age, sex, and body mass index. Body composition was measured using a 3-compartment model based on air-displacement plethysmography to assess body volume and deuterium dilution to assess total body water. The fat-free mass index (FFMI; fat-free mass divided by height squared) and the percent fat mass (%FM) were calculated. Daily physical activity was assessed for 7 days using a triaxial accelerometer and physical fitness with an incremental test until exertion on a bicycle ergometer. Blood samples were taken to determine C-reactive protein (CRP) level and tumor necrosis factor α.


RESULTS
Accelerometer output (kilocounts/day) showed the same physical activity level for patients and controls (mean ± SD 319 ± 105 versus 326 ± 66). There was no difference in the FFMI or %FM between the patients and controls. Physical activity was positively related to the FFMI (partial R = 0.38, P = 0.01) and inversely related to CRP level (R = -0.39, P < 0.01), independent of group. CRP level was inversely related to the FFMI, but the effect was less strong than with physical activity (partial R = -0.31, P = 0.03).


CONCLUSIONS
Daily physical activity may help preserve fat-free mass in patients with AS.
Maastricht University Medical Centre, Maastricht, The Netherlands. g.plasqui@maastrichtuniversity.nl
G
G
Plasqui
A
A
Boonen
P
P
Geusens
E J
EJ
Kroot
M
M
Starmans
S
S
van der Linden
D056044:Actigraphy / Q000295:instrumentation; D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D015992:Body Mass Index; D001834:Body Water / Q000378:metabolism; D002097:C-Reactive Protein / Q000032:analysis; D016022:Case-Control Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009426:Netherlands; D010991:Plethysmography; D013167:Spondylitis, Ankylosing / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D055815:Young Adult
D015415:Biomarkers; D018836:Inflammation Mediators; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein