Disrupting sleep and circadian rhythms alters bone metabolism

By Anne Harding

NEW YORK (Reuters Health) – Circadian disruption and sleep restriction could lead to bone loss over time, with particularly strong effects in younger men, new research shows.

“Three weeks of circadian disruption with concurrent sleep restriction (like rotating shiftwork) decreased a marker of bone formation while a marker of bone resorption was unchanged in 10 healthy men,” Dr. Christine Swanson of the University of Colorado School of Medicine in Aurora told Reuters Health by email. “If sustained, this could lead to a loss of bone mass.”

Sleep duration, both short and long, has been associated with low bone mineral density (BMD), Dr. Swanson and her team note in their report, published in the Journal of Clinical Endocrinology and Metabolism, online July 26. Also, they point out, rotating shiftwork is associated with a higher risk of fracture.

The men in the study included six who were in their twenties and four who ranged in age from 55 to 65. The men spent about three weeks in an inpatient lab under a “forced desynchrony” protocol, which included 28-hour sleep-wake cycles with 21.47 hours awake and 6.53 hours asleep. This was equivalent to getting about 5.6 hours of sleep a night.

Levels of N-terminal Propeptide of type I collagen (P1NP), a marker of bone formation, were lower after the intervention, the researchers found. The average decrease for the younger men was 28.0%, compared to 18.2% for the older men. Levels of C-terminal cross-linked telopeptide of type 1 collagen (CTX), a marker of resorption, were unchanged. Younger men showed a 22.9% increase in sclerostin, a marker for osteocyte function, but sclerostin levels did not change in the older men.

The findings suggest that the effects of circadian disruption and sleep restriction are stronger in younger men, who are experiencing bone consolidation, a critical time for building optimal bone mass, Dr. Swanson and her team note.

“These preliminary data may indicate that sleep and circadian disruption are additional, unrecognized risk factors for osteoporosis,” the researcher said. “We are working to confirm and extend these findings to other populations (e.g., women) and evaluate the mechanisms to explain how sleep and circadian disruption alter bone turnover.”

SOURCE: http://bit.ly/2hDIzHO

J Clin Endocrinol Metab 2017.

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