Could Getting Enough Sleep Help Prevent Osteoporosis?

Osteoporosis is a common skeletal disease in which the bone mass decreases and the bone substance becomes porous. The disease reduces bone density and strength, causing bones to become brittle and unstable. At the University of Colorado School of Medicine’s annual Research Day, held April 23, faculty member Christine Swanson, MD, MCR, an associate professor in the Department of Endocrinology, Metabolism and Diabetes, presented her National Institutes of Health-funded clinical research on whether adequate sleep can help prevent osteoporosis.

Decreasing Bone Density and Less Total Sleep Time

Osteoporosis can occur for many reasons, such as hormonal changes, ageing and lifestyle factors. Sometimes, however, there is no explanation for the disease. That’s why Swanson says it’s important to look for new risk factors and consider what else changes throughout life, like bones – sleep being one of them.

In their early to mid-20s, people reach what is known as peak bone density, which is higher in men than in women. This peak value is one of the main factors for fracture risk in later life. After reaching this peak, a person’s bone melatonin remains roughly stable for several decades. Then, when women reach the menopause, bone loss accelerates. The bone density of men also decreases with age. Sleeping habits also change over time. With increasing age, the total duration of sleep decreases and the composition of sleep changes. For example, sleep latency, i.e. the time it takes to fall asleep, increases with age. On the other hand, slow-wave sleep, i.e. deep, restorative sleep, decreases with age. And it is not only the duration and composition of sleep that changes. Circadian phase preference also changes throughout life for both men and women, according to Swanson, and she was referring to people’s preference for when they go to sleep and when they wake up.

How Sleep Affects Bone Health

Genes that control our internal clock are present in all our bone cells. When these cells resorb and form bone, they release certain substances into the blood that can be used to estimate how much bone turnover is taking place at any given time. These markers of bone resorption and formation follow a daily rhythm. The amplitude of this rhythm is greater for the markers of bone resorption – which relates to the process of bone resorption – than for the markers of bone formation. This rhythmicity is likely important for normal bone metabolism and suggests that sleep and circadian disruption may directly influence bone health.

To better understand this relationship, Swanson and colleagues examined how markers of bone turnover responded to cumulative sleep restriction and circadian rhythm disruption. For this study, participants lived in a fully controlled inpatient environment. They did not know what time it was, and they were put on a 28-hour schedule instead of a 24-hour day.

According to the researchers, this disruption to the circadian system is designed to simulate the stresses of working rotating night shifts and is roughly equivalent to flying through four Western time zones every day for three weeks. The protocol also resulted in the participants getting less sleep. The research team measured bone turnover markers at the beginning and end of the intervention and found that there were significant adverse changes in bone turnover in both men and women in response to sleep and circadian rhythm disruption. Adverse changes included decreases in markers of bone formation that were significantly more pronounced in younger individuals of both sexes than in older individuals.

In addition, young women showed a significant increase in the bone resorption marker. According to Swanson, if a person forms less bone while resorbing the same amount – or even more – this could lead to bone loss, osteoporosis and an increased risk of fracture over time. Gender and age may also play an important role, with younger women possibly being the most susceptible to the damaging effects of poor sleep on bone health.