A shift-based job or frequent travelling that causes jet lag poses continuous restriction on good sleep as well as disruptions in the internal body clock, and might be an unrecognised factor for bone loss in young men, researchers say.The finding showed that young men with sleep restriction and circadian disruption had 27 per cent greater reduction in level of P1NP -- a marker of bone formation in blood -- compared to 18 per cent in older men. Circadian disruption was defined as "a mismatch between internal body clock and the environment caused by living on a shorter or longer day than 24 hours."On the other hand, the levels of the bone resorption marker -- CTX -- remained unchanged, an indication that old bone could break down without new bone being formed, the researchers said.
"This altered bone balance creates a potential bone loss window that could lead to osteoporosis -- a condition in which bones become weak and brittle and causes fractures," said lead investigator Christine Swanson, Assistant Professor at the University of Colorado in Aurora, US."The 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 added.For the study, presented at the Endocrine Society's 99th annual meeting in Orlando, the team evaluated health consequences of sleep restriction combined with circadian disruption.Participants 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". The men were allowed to sleep only 5.6 hours per 24-hour period -- similar to those working in night shifts and having jet lag as a result of increased flying hours.