Abstract
Longitudinal studies provide unique insights into the impact of environmental factors and lifespan issues on health and disease. Here we investigate changes in body composition in 3088 free-living participants, part of the UK Biobank in-depth imaging study. All participants underwent neck-to-knee MRI scans at the first imaging visit and after approximately two years (second imaging visit). Image-derived phenotypes for each participant were extracted using a fully-automated image processing pipeline, including volumes of several tissues and organs: liver, pancreas, spleen, kidneys, total skeletal muscle, iliopsoas muscle, visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue, as well as fat and iron content in liver, pancreas and spleen. Overall, no significant changes were observed in BMI, body weight, or waist circumference over the scanning interval, despite some large individual changes. A significant decrease in grip strength was observed, coupled to small, but statistically significant, decrease in all skeletal muscle measurements. Significant increases in VAT and intermuscular fat in the thighs were also detected in the absence of changes in BMI, waist circumference and ectopic-fat deposition. Adjusting for disease status at the first imaging visit did not have an additional impact on the changes observed. In summary, we show that even after a relatively short period of time significant changes in body composition can take place, probably reflecting the obesogenic environment currently inhabited by most of the general population in the United Kingdom.
Highlights
Longitudinal studies provide unique insights into the impact of environmental factors and lifespan issues on health and disease
The UK Biobank is a unique resource originally designed to enable the in-depth study of a large cohort of the UK population in a cross-sectional manner[6,8]
In this study we generated multiple organ IDPs14 and examined whether these changed over the study period (< 3 years )
Summary
Longitudinal studies provide unique insights into the impact of environmental factors and lifespan issues on health and disease. Long-term cohort studies tracking changes in adipose tissue and ectopic fat such as KORA (Cooperative Health Research in the Region of Augsburg) or Study of Health in Pomerania (SHIP), which includes whole-body MRI, have only obtained MRI measurements at a single time p oint[3,4] Others such as the Dallas Heart S tudy[5] undertook longitudinal MRI that included whole-body and liver fat measurements, but like other cohorts this study focussed on heart and vessel health and did not make detailed measurements of other abdominal organs. The advent of deep learning methods, applied to the analysis of large MRI datasets, has made the measurement of multiple abdominal organs at scale a possibility This is essential in light of the growing number of population-based cohorts world wide such as the UK Biobank[6] and German National C ohort[7]. The UK Biobank imaging study, originally designed to be cross-sectional with 100,000 participants has expanded its original remit to include an additional imaging visit for the whole cohort, approximately four to five years after the initial scan[8]. We found that the trajectory of longitudinal changes in body-composition IDPs was dependant on the physiological state of the participants
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