Increased sitting time was associated with lower baseline femoral neck (BMD) in a cohort of 8,272 participants.
Women with higher levels of sitting had lower adjusted femoral neck BMD compared to those with the least sitting.
Men in the third quartile of sitting also showed lower adjusted femoral neck BMD than those in the first quartile.
No significant relationship was found between baseline or stable sitting and changes in BMD over ten years.
There was no increased risk of fragility fractures associated with levels of sitting over the ten-year period.
The findings suggest that habitual sitting behavior may impact baseline bone health but not fracture risk or BMD loss over time.
Simplified
(SB) or sitting is associated with multiple unfavorable health outcomes. Bone tissue responds to imposed gravitational and muscular strain with there being some evidence suggesting a causal link between SB and poor bone health. However, there are no population-based data on the longitudinal relationship between SB, bone change, and incidence of fragility fractures. This study aimed to examine the associations of sitting/SB (defined as daily sitting time), areal (by DXA), and incident low trauma (fragility) osteoporotic fractures (excluding hands, feet, face, and head). We measured baseline (1995-7) and 10-yr self-reported SB, femoral neck (FN), total hip (TH), and lumbar spine (L1-L4) BMD in 5708 women and 2564 men aged 25 to 80+ yr from the population-based, nationwide, 9-center Canadian Multicentre Osteoporosis Study. Incident 10-yr data were obtained from 4624 participants; >80% of fractures were objectively confirmed by medical records or radiology reports. Vertebral fractures were confirmed by qualitative morphological methods. All analyses were stratified by sex. Multivariable regression models assessed SB-BMD relationships; Cox proportional models were fit for fracture risk. Models were adjusted for age, height, BMI, physical activity, and sex-specific covariates. Women in third/fourth quartiles had lower adjusted FN BMD versus women with the least SB (first quartile); women in the SB third quartile had lower adjusted TH BMD. Men in the SB third quartile had lower adjusted FN BMD than those in SB first quartile. Neither baseline nor stable 10-yr SB was related to BMD change nor to incident fragility fractures. Increased sitting (SB) in this large, population-based cohort was associated with lower baseline FN BMD. Stable SB was not associated with 10-yr BMD loss nor increased fragility fracture. In conclusion, habitual adult SB was not associated with subsequent loss of BMD nor increased risk of fracture.
Key numbers
Lower in third and fourth quartiles vs. first quartile
Adjusted FN Decrease in Women
Comparison of femoral neck across quartiles in women.
Lower in third quartile vs. first quartile
Adjusted FN Decrease in Men
Comparison of femoral neck across quartiles in men.
0.92 (0.74–1.15) for clinical fragility fractures
No Association with Fracture Risk
Hazard ratio for clinical fragility fractures across quartiles in women.
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None of the authors have commercial or other conflicts of interest related to these data. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. S.L.G. has a position with Sidekick Health, Iceland. D.G. has been a consultant for Amgen, Eli Lilly, Merck, and Novartis. C.S.K/. has received honoraria for advisory boards, consultancies, or speaker’s fee from Amgen, Abbott, Danone, Eli Lilly, Merck, and Novartis. K.S.D. has served as advisory board member/received honoraria from Amgen, Merck, Proctor & Gamble, Sanofi-Aventis, and Servier. S.M.K. has served as advisory board member/received honoraria from Amgen, Eli Lilly, Novartis, and Warner-Chilcott. Eli Lilly, Novartis, Proctor & Gamble, Sanofi-Aventis, Servier, and Wyeth-Ayerst. S.N.M. has received research grants from Amgen, Eli Lilly, Merck, and Novartis. J.D.A. has received research grants and/or personal fees from Amgen, Eli Lilly, Merck, Actavis, and AgNovos. J.C.P., C.B., H.M., and W.M.H. report no conflicts of interest.
