Defining reference values for body composition indexes by magnetic resonance imaging in UK Biobank

BackgroundMagnetic resonance imaging (MRI) is the gold standard for body composition measurements, while such reference range data have not been reported yet. MethodsWe used MRI-measured body composition data from the UK Biobank cohort, including three lean tissue parameters and seven adipose tissue parameters. Participants aged between 45 to 74 years from both genders with at least one parameter data were screened. Age- and sex-specific percentile curves were generated by the lambda-mu-sigma method. Three levels of reference ranges were provided, which were equivalent to mean {+/-} 1 standard deviation (SD), 2 SDs, and 2.5 SDs, respectively. ResultsThe final analysis set for each parameter ranged from 4 842 to 14 148 participants (53.4-56.6 % women) with median ages around 61 years after eligibility confirmation. For lean tissue parameters, from age 45 to age 70, median percentiles of total lean tissue volume and total thigh fat-free muscle volume reduced by 2.83 L and 1.73 L in men, and by 3.02 L and 1.51 L in women, respectively. Within the age range, median percentiles of weight-to-muscle ratio elevated by 0.51 kg/L in men and 0.83 kg/L in women, respectively. Adipose tissue parameters presented inconsistent trajectories. For men, median percentiles of muscle fat infiltration, visceral adipose tissue (VAT) volume, total abdominal adipose tissue index, and abdominal fat ratio elevated by 1.48 %, 0.32 L, 0.08 L/m2 and 0.04, while abdominal subcutaneous adipose tissue (ASAT) volume and total adipose tissue volume reduced by 0.47 L and 0.41 L from age 45 to age 70, respectively. And total trunk fat volume remained stable with aging (approximate 9.52 L). For women, muscle fat infiltration and VAT volume showed similar trends with men, increased by 1.68 % and 0.76 L from age 45 to age 70. Other five parameters firstly increased from age 45 to age 60 (ASAT volume: 0.35 L, total adipose tissue volume: 0.78 L, total trunk fat volume: 1.12 L, total abdominal adipose tissue index: 0.49 L/m2, and abdominal fat ratio: 0.06), then kept stable (total abdominal adipose tissue index and abdominal fat ratio) or presented a slight reduction afterwards (ASAT volume: 0.33 L, total adipose tissue volume: 0.14 L, and total trunk fat volume: 0.20 L). ConclusionsWe have established reference ranges for MRI-measured body composition parameters based on large community-dwelling population. The data would benefit more accurate assessment of abnormal adipose and muscle conditions.