Researchers from the International University of Health and Welfare offer fresh insights into the consequences of nightly rest.
Osteoporosis in the Japanese population
Osteoporosis has emerged as a prevailing global public health concern, with its incidence steadily increasing. In Japan, a nation marked by an aging demographic, osteoporosis affects 10% of the entire population, with women aged 70 and older accounting for approximately 40% of cases.
This elevated prevalence of osteoporosis imposes substantial strains on the well-being of elderly individuals, leading to escalated healthcare expenditures and a heightened caregiver burden. Hence, there is a need to emphasise the preservation of bone health and the implementation of preventative measures to combat osteoporotic fractures.
In a study recently published in JBMR Plus, a team of researchers from the International University of Health and Welfare in Tokyo investigated the association between inadequate sleep and bone mineral density (BMD) using data collected from annual health check-ups conducted in Japan between 2020 and 2022.
The study was based on a comprehensive analysis that involved 896 men and 821 women, with the median age of 54 for men and 55 for women. It accounted for a multitude of factors including age, body mass index, physical activity, smoking status, alcohol intake for both men and women, and menopausal status for women.
“We categorised daily sleep duration into various groups: less than 5 hours, 5 to less than 7 hours, 7 to less than 9 hours—which served as the reference point—and 9 hours or more,” shared Reiko Yamaura, lead author of the study.
Impact of Sleep Duration on Women’s Bone Health
Yamaura and her team found that around 80% of both men and women slept for less than seven hours on a daily basis. For men, there was no significant association between sleep duration and BMD. However, when it came to women who slept between 5 to less than 7 hours a night, a significantly higher BMD—a 3.9% increase compared to women who slept between 7 to less than 9 hours—was observed.
Surprisingly, no correlation was found between insomnia and BMD in either gender.
Exploring the Relationship Between Sleep and Bone Health
“This revelation not only has implications for the well-being of the Japanese population but also challenges the perception of sleep as a potential threat to bone health,” said Yamamura. “In Japan, the overall average daily sleep duration is shorter compared to global norms. Yet, we found that this abbreviated rest is not independently linked to lower BMD.”
Nonetheless, the researchers noted that while these findings might change the way we view the relationship between sleep and bone health, it is vital to approach them with caution.
“Previous research has suggested that both shorter and longer sleep durations might contribute to increased risk of adverse health conditions, such as cardiovascular problems.” said Tsutomu Yamazaki, senior and corresponding author of the study. “These conflicting findings hint at the complex nature of the interplay between sleep, bone health and overall well-being. It’s a field that’s ripe for further exploration, as scientists worldwide seek to unveil the intricate mechanisms governing our bodies.”