Lack of sleep due to shift work, travel may up bone loss risk

Prolonged sleep disturbances similar to that seen in jet lag or shift work may be increase the risk for bone loss, a new study has found.

Researchers including those from University of Colorado in the US made study subjects stay 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."

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 between 20 to 27 and the other four were aged between 55 to 65.

The group plans to study sex differences in the sleep-bone relationship in subsequent studies.

Researchers found that after three weeks, all men had significantly reduced levels of a bone formation marker called P1NP compared with baseline.

This decline was greater for the younger men than the older men: a 27 per cent versus 18 per cent decrease, researchers said.

"This altered bone balance creates a potential bone loss window that could lead to osteoporosis and bone fractures," said Christine Swanson of University of Colorado.

Levels of the bone resorption marker CTX remained unchanged, an indication that old bone could break down without new bone being formed, researchers said.

"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," Swanson said.