Insufficient sleep, a common problem that has been linked to chronic disease risk, might also be an unrecognised risk factor for bone loss.
Study investigators in the US found that healthy men had reduced levels of a marker of bone formation in their blood after three weeks of cumulative sleep restriction and circadian disruption, similar to that seen in jet lag or shift work, while a biological marker of bone resorption, or breakdown, was unchanged.
“This altered bone balance creates a potential bone loss window that could lead to osteoporosis and bone fractures,” said lead investigator Christine Swanson, assistant professor at the University of Colorado in Aurora.
Study subjects stayed in a lab, where for three weeks they went to sleep each day four hours later than the prior day, resulting in a 28-hour “day.” Swanson likened this change to “flying four time zones west every day for three weeks”.
The men were allowed to sleep only 5.6 hours per 24-hour period, since short sleep is also common for night and shift workers. While awake, the men ate the same amounts of calories and nutrients throughout the study. Blood samples were obtained at baseline and again after the three weeks of sleep manipulation for measurement of bone biomarkers. Six of the men were aged 20 to 27, and the other four were aged 55 to 65.
After three weeks, all men had significantly reduced levels of a bone formation marker called P1NP compared with baseline, the researchers reported. This decline was greater for the younger men than the older men: a 27 per cent versus 18 per cent decrease. She added that levels of the bone resorption marker CTX remained unchanged, an indication that old bone could break down without new bone being formed.
“These data suggest that sleep disruption may be most detrimental to bone metabolism earlier in life, when bone growth and accrual are crucial for long-term skeletal health,” she said. “Further studies are needed to confirm these findings and to explore if there are differences in women.”
Source: The Endocrine Society
