Computed tomography-based skeletal muscle and adipose tissue attenuation: Variations by age, sex, and muscle.

OBJECTIVE:This study aimed to investigate how skeletal muscle attenuation and adipose tissue (AT) attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle vary according to the targeted muscles, sex, and age. DESIGN:Population-based cross-sectional study. SETTING:Community-dwelling old population in Reykjavik, Iceland. SUBJECTS:A total of 5331 older adults (42.8% women), aged 66-96 years from the Age, Gene/Environment Susceptibility (AGES)- Reykjavik Study, who participated in the baseline visit (between 2002 and 2006) and had valid thigh and abdominal computed tomography (CT) scans were studied. METHODS:Muscle attenuation and AT attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle were determined using CT. Linear mixed model analysis of variance was performed for each sex, with skeletal muscle or AT attenuation as the dependent variable. RESULTS:Muscle attenuation decreased, and AT attenuation increased with age in both sexes, and these differences were specific for each muscle, although not in all age groups. Age-related differences in muscle and AT attenuation varied with specific muscle. In general, for both sexes, skeletal muscle attenuation of the hamstrings declined more than average with age. Men and women displayed a different pattern in the age differences in AT attenuation for each muscle. CONCLUSIONS:Our data support the hypotheses that skeletal muscle attenuation decreases, and AT attenuation increases with aging. In addition, our data add new evidence, supporting that age-related differences in skeletal muscle and AT attenuation vary between muscles.