The effects of anthropometrics, lifting strength, and physical activities in disc degeneration.
METHODS
A cross-sectional study design was used.


OBJECTIVE
The objective was to examine the influences of body anthropometrics, axial disc area, and lifting strength on disc degeneration and to compare these with the effects of lifetime physical demands and age.


BACKGROUND
Although recent studies have shown that heredity is a dominant factor in disc degeneration, the common notion that occupational physical loading is the major risk factor persists. However, substantial variations in disc degeneration, particularly at the lowest lumbar levels, remain unexplained by heredity or occupational physical demands.


METHODS
Univariate methods and stepwise multiple regression modeling were used to estimate associations of body height, weight, fat content, axial disc area, isokinetic lifting performance, and lifetime routine physical activities at work and leisure with disc height narrowing and disc signal (in T2 images) based on lumbar MRIs. These data were available from a population sample of 600 men, 35 to 70 years of age.


RESULTS
Lower disc signal, representing disc desiccation, was associated with higher age, lower body mass and lifting strength, and larger axial disc area. Of the variance in disc signal, age explained 8.0% (P < 0.001) and body weight/axial disc area, isokinetic lifting strength, and occupational lifting history added 3.9%, 2.3%, and 1.3%, respectively. Greater disc narrowing was associated with higher age, larger axial disc area, and higher occupational physical loading. Of the variance in disc narrowing, age accounted for 3.8% (P < 0.001); axial disc area and occupational loading added 1.9% (P < 0.004) and 1.3% (P < 0.007), respectively.


CONCLUSIONS
Body weight, lifting strength, and axial disc area were more highly associated with disc degeneration than occupational and leisure physical activity histories, although all had modest influences. Furthermore, higher body mass, greater lifting strength, and heavier work were all associated with more disc height narrowing but less disc desiccation contrary to current views. Smaller discs appeared to have beneficial effects.
Videman
Tapio
T
University of Alberta, Edmonton, Alberta, Canada. tapio.videman@ualberta.ca
Levälahti
Esko
E
Battié
Michele C
MC
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000886:Anthropometry; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology*; D007899:Leisure Activities; D017770:Lifting / Q000009:adverse effects*; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D015999:Multivariate Analysis; D009784:Occupational Diseases / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D012044:Regression Analysis; D012307:Risk Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D016474:Weight-Bearing