Long-term effect of physical inactivity on osteosarcopenic obesity - a MRI-based investigation from a population-based cohort.

BACKGROUND: The hazardous triad of osteopenia, sarcopenia and obesity was recently defined as osteosarcopenic obesity (OSO). The causes for OSO appear to be multifactorial, including age and gender, as well as chronic diseases. The impact of physical inactivity has not been studied so far. PURPOSE: The purpose of this study was to assess the association of short-term and long-term physical inactivity over a time period of 14 years on osteosarcopenic obesity in a population-based cohort from southern Germany. METHODS: Supine whole body MRI (3 T scanner, Magnetom Skyra, Siemens Healthcare) was performed in 400 subjects from the population-based observational cohort study "Kooperative Gesundheitsforschung in der Region Augsburg (KORA)" to determine bone marrow fat fraction (BMFF), skeletal muscle fat fraction (SMFF) and total adipose tissue (TAT). Based on this, phenotyping was conducted into the groups of the OSO complex. Physical inactivity was obtained via a questionnaire at three timepoints: exam 1 (1999 to 2001), exam 2 (2006 to 2008) and exam 3 (2013 and 2014). RESULTS: In total, 363 subjects (56.0 ± 9.1 years, 57.6% male) were included. The OSO phenotype was fully expressed in 81 (22,3%) participants. All pathological subgroups of the OSO complex, except isolated obesity were associated with less physical activity (< 1 h/week) at exam 3. Work activity correlated with the isolated osteopenic and sarcopenic phenotypes, as well as OSO, whereas neither walking, nor cycling activity correlated significantly with any phenotypic subgroup. Similarly, long-term physical inactivity was accompanied by isolated osteopenia, sarcopenia and osteosarcopenic obesity but not with isolated obesity. Lower back pain was present in 54.5% of all participants at exam 3. No correlation was shown with the OSO complex. CONCLUSION: Physical inactivity was strongly correlated with an isolated osteopenic, sarcopenic and OSO phenotype, but not with an isolated obese phenotype by MRI. Although slightly over fifty percent of participants reported back pain on exam 3, the manifestation of the OSO complex had no effect on this.