Age-related Fatty Infiltration of Lumbar Paraspinal Muscles: a Normative Reference Database Study in 516 Chinese Females

Background: Fatty infiltration, as a result of aging, is an essential biomarker of muscle degeneration. This research aimed to investigate the age-dependent change of fatty degeneration in the paraspinal muscles of healthy Chinese women. This study also explores the effect of body size on fatty infiltration of paraspinal muscles.

Methods: Cross-sectional area of paraspinal muscles (CSA) and intermuscular adipose tissue (CSA) were measured at the L3 mid-vertebral level of 516 healthy females, who underwent abdomen quantitative computed tomography (QCT) scans. Subsequently, IMAT% [CSA / (CSA + CSA)] were calculated. The relationship between basic information and measurements was evaluated using Spearman correlations. Comparisons of QCT results among different BMI subgroups in different age groups were analyzed with the Kruskal-Wallis H test and LSD, post-hoc correction. Age-related changes were calculated after the adjustment of height and weight.

Results: The mean CSA of 20-29 years group (n=69) and 70-79 years group (n=25) were 3.00 cm and 11.06 cm, respectively. While the mean CSA of 20-29 years group was 38.46 cm and 70-79 years group was 30.86 cm. The mean IMAT% difference between 20-29 years group and 70-79 years group was -18.55%. Strong, positive non-linear associations were observed between ageing and CSA, along with IMAT% (r=0.656, P<0.01; r=0.714, P<0.01). However, CSA was shown to decrease with age in a weak, negative linear fashion (r=-0.265, P<0.01). Positive relationships between BMI and CSA, CSA, along with IMAT%, were found. Significant differences were observed between obesity and normal BMI subgroup for all variables in three age groups. CSA showed a larger age-related difference compared to CSA.

Conclusions: Fatty infiltration in paraspinal muscles increased with age and BMI, while muscle loss may be associated with aging. The present study provided standardized reference data for the fatty degeneration of paraspinal muscles across the adult lifespan of Chinese females, which will play a critical role in future studies.