Sedentary behavior does not predict low BMD nor fracture-population-based Canadian Multicentre Osteoporosis Study

Area of Science:

• Bone Health and Osteoporosis Research
• Epidemiology and Public Health
• Gerontology and Aging Studies

Background:

• Sedentary behavior (SB) is linked to adverse health outcomes, including potential negative effects on bone health.
• Existing evidence suggests a connection between sedentary time and poor bone mineral density (BMD).
• Population-based longitudinal data on SB, bone changes, and fragility fractures are lacking.

Purpose of the Study:

• To investigate the longitudinal associations between daily sitting time (sedentary behavior), bone mineral density (BMD), and the incidence of low-trauma osteoporotic fractures.
• To examine how changes in sedentary behavior over time relate to bone health and fracture risk in a large cohort.

Main Methods:

• Utilized data from the Canadian Multicentre Osteoporosis Study (CaMOS) including 5708 women and 2564 men (aged 25-80+).
• Measured self-reported sedentary behavior (sitting time) and areal BMD (DXA) at baseline and 10-year follow-up.
• Assessed incident fragility fractures over 10 years, with >80% confirmed by medical records; analyzed relationships using multivariable regression and Cox proportional models, stratified by sex and adjusted for covariates.

Main Results:

• Increased sitting time at baseline was associated with lower femoral neck (FN) BMD in women and men, and lower total hip (TH) BMD in women.
• Neither baseline nor stable 10-year sedentary behavior was associated with BMD change over the decade.
• No significant relationship was found between sedentary behavior (baseline or stable) and the incidence of fragility fractures over 10 years.

Conclusions:

• Habitual adult sedentary behavior is associated with lower baseline bone mineral density, particularly at the hip.
• However, sedentary behavior was not found to predict subsequent bone loss or increase the risk of fragility fractures over a 10-year period.
• These findings suggest that while sedentary time may impact baseline bone density, it may not be a primary driver of bone loss or fracture incidence in the long term.