Does Subjective Sleep Affect Bone Mineral Density in Older People with Minimal Health Disorders? The PROOF Cohort

The Association between Sleep and Bone Mineral Density: Cross-Sectional Study Using Health Check-up Data in a Local Hospital in Japan

This study aimed to investigate the association between daily sleep duration of <7 hours and lower bone mineral density (BMD) using data from annual health check-ups conducted in Japan between 2020 and 2022. Multivariate regression models were used, where BMD was the objective variable and daily sleep duration (<5 hours, 5 to <7 hours, 7 to <9 hours [reference], ≥9 hours) was the exposure variable adjusted for age, body mass index, physical activity, smoking status, and alcohol intake for men and women and further adjusted for menopausal status for women. The association between insomnia and BMD was also investigated. BMD was determined using calcaneal quantitative ultrasound and expressed as a percentage of the young adult mean (%YAM). In total, 896 men and 821 women were included. Median age was 54 years (interquartile range [IQR]: 46 to 64) for men and 55 years (IQR: 46 to 64) for women). Median BMD for men and women was 79%YAM (IQR: 71 to 89) and 75%YAM (IQR: 68 to 84), respectively. Approximately 80% of men and women slept <7 hours daily. Multivariate regression showed no association between sleep duration and BMD in men. However, women who slept 5 to <7 hours daily had significantly higher BMD by 3.9% compared with those who slept 7 to<9 hours (p = 0.004). No association between insomnia and BMD was found. Overall, a daily sleep duration of <7 hours was not independently associated with lower BMD compared to those who slept 7 to <9 hours in men and women. However, as there is evidence of both shorter and longer sleep durations being associated with an increased risk of adverse events, including cardiovascular events, our result needs to be interpreted with caution. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Self-reported sleep characteristics and risk for incident vertebral and hip fracture in women

OBJECTIVE

To examine the relationships between self-reported sleep characteristics and risk of incident vertebral fracture and hip fracture in women.

DESIGN

Longitudinal cohort study.

SETTING

Nurses' Health Studies (NHS: 2002-2014, NHSII: 2001-2015).

PARTICIPANTS

Total 122,254 female registered nurses (46,129 NHS, 76,125 NHSII) without prior history of fracture.

EXPOSURE

Sleep was characterized by 4 sleep-related domains-sleep duration, sleep difficulty, snoring, and excessive daytime sleepiness-assessed by self-reported questionnaires.

OUTCOMES

Self-reports of vertebral fracture were confirmed by medical record review and hip fracture was assessed by biennial questionnaires.

RESULTS

Over 12-14 years of follow-up, 569 incident vertebral fracture cases (408 in NHS, 161 in NHSII) and 1,881 hip fracture cases (1,490 in NHS, 391 in NHSII) were documented. In the pooled analysis, the multivariable-adjusted HR (95% CI) for vertebral fracture was 1.20 (0.86, 1.66) for sleep duration ≤5 hours vs. 7 hours and 0.82 (0.60, 1.12) for ≥9 vs. 7 hours; 1.63 (0.93, 2.87) for sleep difficulties all-the-time vs. none/little-of-the-time (p-trend = 0.005); 1.47 (1.05, 2.05) for snoring every night/week vs. never/occasionally (p-trend = 0.03), and 2.20 (1.49, 3.25) for excessive daytime sleepiness daily vs. never (p-trend < 0.001). In contrast, associations were not observed with hip fracture risk.

CONCLUSION

Poorer sleep characteristics were associated with risk of vertebral fracture. Our study highlights the importance of multiple dimensions of sleep in the development of vertebral fractures. Further research is warranted to understand the role of sleep in bone health that may differ by fracture site, as well as sleep interventions that may reduce the risk of fracture.

Association of Sleep Traits and Heel Bone Mineral Density: Observational and Mendelian Randomization Studies

Observational studies have suggested that sleep and circadian disturbances are potentially modifiable risk factors for low bone mineral density (BMD), but the causal relationship is unclear. This study aimed to (i) replicate the findings by examining observational association of sleep traits with low estimated BMD); (ii) examine whether these associations were causal by using Mendelian randomization (MR) analyses; and (iii) investigate potential modulation effects of sex and menopause. A total of 398,137 White British subjects (aged 39 to 73 years) with valid BMD estimated by quantitative ultrasound of the heel (eBMD) at baseline were included. Linear regression analyses and inverse-variance weighted method were used as main methods for observational and one-sample MR analyses, respectively, to investigate the associations between self-reported sleep traits (sleep duration, chronotype, daytime sleepiness, and insomnia) and low eBMD. Furthermore, sensitivity analyses were performed in subgroups based on sex and menopause in both observational and MR analyses. In observational analyses, short/long sleep, insomnia, and definite eveningness were associated with low eBMD (short sleep: β = -0.045, effect in standard deviation change of rank-based inverse normally transformed eBMD; long sleep: β = -0.028; sometimes insomnia: β = -0.012; usually insomnia: β = -0.021; definite eveningness: β = -0.047), whereas definite morningness was associated with decreased risk of low eBMD (β = 0.011). Subgroup analyses suggested associations of short/long sleep and definite eveningness with low eBMD among men, short sleep with low eBMD among premenopausal women, and short sleep, eveningness, and daytime sleepiness among postmenopausal women. In bidirectional MR analyses, there was no causal relationship between sleep traits and eBMD in either overall sample or subgroup analyses. In summary, although observational analysis showed a robust association of low eBMD with sleep duration, chronotype, and insomnia, there was no evidence of causal relationship as suggested by MR analysis. © 2021 American Society for Bone and Mineral Research (ASBMR).

Sleep disruptions and bone health: what do we know so far?

PURPOSE OF REVIEW

This review briefly summarizes the growing body of literature addressing the skeletal consequences of sleep and circadian disruption.

RECENT FINDINGS

The most recent data in the field suggest that the diurnal variation in bone turnover markers are because of endogenous circadian rhythmicity linked to clock genes in all bone cells; in a small human intervention study, cumulative sleep restriction with concurrent circadian disruption negatively alter bone turnover markers in a way that could explain the lower BMD and increased fracture risk identified in some prior night shift work studies; abnormal sleep duration and obstructive sleep apnea are associated with low BMD and increased fracture risk in some but not all studies.

SUMMARY

Normal physiology and some animal and human intervention studies suggest that sleep and circadian disruptions, such as night shift work, abnormal sleep durations and obstructive sleep apnea are detrimental to skeletal health. However, additional research in this area is needed to determine which sleep/circadian disturbances are most detrimental to skeletal health, the reversibility of such impairments, and underlying mechanisms.

Sleep disturbance and bone mineral density, risk of falls and fracture: Results from a 10.7-year prospective cohort study

Sleep problems are common in the general population and have been linked to bone health, falls risk and fracture. However, longitudinal studies on sleep-bone health outcomes are lacking and no study has investigated whether an increased risk of fracture is attributable to sleep-related low bone mineral density (BMD) and an increased risk of falls. This study was designed to examine the associations of sleep disturbance with bone mineral density (BMD), risk of falls and fractures over 10.7 years. The analyses were performed in a population-based cohort study with 1099 participants (mean age 62.9 years) enrolled at baseline, and 875, 768 and 563 participants traced at a mean follow-up of 2.6, 5.1 and 10.7 years, respectively. At each visit, self-reported sleep disturbance was recorded. BMD (by dual-energy x-ray absorptiometry), falls risk score and fracture were measured at each visit. The short-form Physiological Profile Assessment was used to measure falls risk score expressed as Z-score. Fractures were self-reported. Mixed-effects model and generalized estimating equations were used for the analyses. In multivariable analysis, there was a dose-response relationship between the extent of sleep disturbance and falls risk score with the strongest association in those reporting the worst sleep disturbance (β = 0.15/unit; 95%CI 0.02-0.28). The worst sleep disturbance was associated with an increased risk of any (relative risk [RR] 1.30/unit; 95%CI 1.01-1.67) and vertebral fracture (RR 2.41/unit; 95%CI 1.00-5.80) compared with those reporting no interrupted sleep. Women but not men with sleep disturbance had a higher risk of vertebral fracture (RR: 2.07 to 6.02, P < 0.05). These were independent of covariates, hip BMD and falls risk. There was no statistically significant association between sleep disturbance and BMD at the hip, spine or total body. Sleep disturbance was independently associated with a greater falls risk score and an increased risk of fractures. Further research is needed to confirm and identify underlying mechanisms for these associations.

A cross-sectional analysis of the association between sleep duration and osteoporosis risk in adults using 2005-2010 NHANES

Controversy remains regarding the relationship between bone health and sleep. In the literature, the effect of sleep on bone density in the clinical setting varies depending on the definition of normal sleep duration, sleep quality, selected population, and diagnostic tools for bone density. The aim of this study was to examine the association between bone mineral density (BMD)assessed by dual-energy X-ray absorptiometry and sleep duration/quality in the defined adult population from the National Health and Nutrition Examination Survey (NHANES) (a national household survey) within a 6-year period (2005–2010) and explore age differences. The basic variables, metabolic diseases, and bone density in the femoral neck as determined through dual-energy X-ray absorptiometry, were segregated, and analyzed according to different sleep durations (1–4, 5–6,7–8, and > 9 h/day) and sleep quality using multinomial regression models. A total of 12,793 subjects were analyzed. Our results reveal that women aged > 50 years with sleep duration < 5 h/day had a 7.35 (CI 3.438–15.715) odds of osteoporosis than those in other groups. This analysis is based on a nationally representative sample using survey and inspection data and clarifies the relationship between bone density and the effect of the combination of sleep quality and duration.

Sleep duration and bone health measures in older men

The associations between objective measures of sleep duration and bone outcomes in older men are unknown. No consistent, significant association was identified between sleep duration and bone mineral density (BMD) in the current analysis. However, future research should determine if vitamin D status modifies this relationship.

INTRODUCTION

Prior studies, predominantly in women, reported that long and short self-reported sleep duration are associated with lower BMD. Associations between actigraphy-determined sleep duration and BMD or bone turnover markers (BTMs) in older men are unknown.

METHODS

Men in The Osteoporotic Fractures in Men (MrOS) Study with wrist actigraphy and concurrent BMD assessment but without comorbidities affecting bone health were included. Sleep duration was considered as a continuous (N = 1926) and dichotomized variable where men were classified as getting the recommended (7-8 h/night; N = 478) or short (< 6 h/night; N = 577) sleep. The cross-sectional association between BMD, BTMs, and sleep duration was examined using a t test or linear regression, where appropriate, in unadjusted and adjusted models.

RESULTS

There were no clinically or statistically significant differences in BMD at the L-spine, total hip, or femoral neck between men getting the recommended vs. short sleep duration, using actigraphy or self-reported sleep duration (all p ≥ 0.07). When sleep duration was considered as a continuous variable, femoral neck BMD was higher in men with longer self-reported sleep duration (β = 0.006 ±0.003, p = 0.02), but this was not significant after further adjustment. In men with low 25OHD (< 20 ng/mL), longer actigraphy-determined sleep duration was associated with higher total hip BMD (β = 0.016 ± 0.008; p = 0.04). Sleep duration and BTMs were not associated.

CONCLUSION

Sleep duration was not associated with hip or L-spine BMD or BTMs in older men. Future research should determine if vitamin D status or other factors modify this relationship.

The "Goldilocks Day" for Children's Skeletal Health: Compositional Data Analysis of 24-Hour Activity Behaviors

Optimization of children's activity behaviors for skeletal health is a key public health priority, yet it is unknown how many hours of moderate to vigorous physical activity (MVPA), light physical activity (LPA), sedentary behavior, or sleep constitute the best day-the "Goldilocks Day"-for children's bone structure and function. To describe the best day for children's skeletal health, we used data from the cross-sectional Child Health CheckPoint. Included participants (n = 804, aged 10.7 to 12.9 years, 50% male) underwent tibial peripheral quantitative CT to assesses cross-sectional area, trabecular and cortical density, periosteal and endosteal circumference, polar moment of inertia, and polar stress-strain index. Average daily time-use composition (MVPA, LPA, sedentary time, and sleep) was assessed through 8-day, 24-hour accelerometry. Skeletal outcomes were regressed against time-use compositions expressed as isometric log-ratios (with quadratic terms where indicated), adjusted for sex, age, pubertal status, and socioeconomic position. The models were used to estimate optimal time-use compositions (associated with best 5% of each skeletal outcome), which were plotted in three-dimensional quaternary figures. The center of the overlapping area was considered the Goldilocks Day for skeletal health. Children's time-use composition was associated with all skeletal measures (all p ≤ 0.001) except cross-sectional area (p = 0.72). Days with more sleep and MVPA, less sedentary time, and moderate LPA were beneficially associated with skeletal measures, except cortical density, which was adversely associated. The Goldilocks daily time-use composition for overall skeletal health was center (range): 10.9 (10.5 to 11.5) hours sleep; 8.2 (7.8 to 8.8) hours sedentary time; 3.4 (2.8 to 4.2) hours LPA, and 1.5 (1.3 to 1.5) hours MVPA. Estimated optimal sleep duration is consistent with current international guidelines (9 to 11 hours), while estimated optimal MVPA exceeds recommendations of at least 60 min/d. This first study to describe optimal durations of daily activities for children's skeletal health provides evidence to underpin guidelines. © 2020 American Society for Bone and Mineral Research (ASBMR).

Higher healthy lifestyle scores are associated with greater bone mineral density in middle-aged and elderly Chinese adults

This study examined the association between healthy lifestyle score (HLS), which contained 7 items (smoking, BMI, physical activity, diet, alcohol, sleep and anxiety) and BMD. Results showed HLS was positively associated with BMD at all studied sites, suggesting that healthier lifestyle patterns might be beneficial to bone health.

PURPOSE

Previous studies have reported favourable associations of individual healthy lifestyle factors with bone mineral density (BMD), but limited evidence showed the relationship of a combined healthy lifestyle score (HLS) with BMD. This study examined the association between the HLS and BMD.

METHODS

This community-based cross-sectional study included 3051 participants aged 40-75 years. The HLS contained 7 items (smoking, BMI, physical activity, diet quality, alcohol intake, sleep and anxiety). BMD values of whole body (WB), lumbar spine 1-4 (L_1-4), total hip (TH) and femur neck (FN) were measured using dual-energy X-ray absorptiometry.

RESULTS

After adjusting for potential covariates, HLS was positively associated with BMD at all studied sites (P-trend < 0.01). The mean BMDs were 2.69% (WB), 5.62% (L_1-4), 6.13% (TH) and 5.71% (FN) higher in participants with HLS of 6-7 points than in those with HLS of 0-2 points. The per 1 of 7 unit increase in the HLS was associated with increases of 7.63 (WB)-13.4 (TH) mg/cm² BMD levels at all sites. These favourable associations tended to be more pronounced in men than in women. Among the 7 items, physical activity contributed most to the favourable associations, followed by BMI, non-smoking and diet; the other three items played little roles. Sensitivity analyses showed that the significant associations remained after excluding any one of the 7 components or excluding fracture subjects at all sites.

CONCLUSION

Higher HLS was associated with greater BMD in middle-aged and elderly Chinese, suggesting that healthier lifestyle patterns might be beneficial to bone health.

Short Sleep Is Associated With Low Bone Mineral Density and Osteoporosis in the Women's Health Initiative

Short sleep duration, recognized as a public health epidemic, is associated with adverse health conditions, yet little is known about the association between sleep and bone health. We tested the associations of usual sleep behavior and bone mineral density (BMD) and osteoporosis. In a sample of 11,084 postmenopausal women from the Women's Health Initiative (WHI; mean age 63.3 years, SD = 7.4), we performed a cross-sectional study of the association of self-reported usual hours of sleep and sleep quality (WHI Insomnia Rating Score) with whole body, total hip, femoral neck, and spine BMD using linear regression models. We also studied the association of sleep duration and quality with dual-energy X-ray absorptiometry (DXA)-defined low bone mass (T-score < -2.5 to <-1) and osteoporosis (T-score ≤ -2.5) using multinomial regression models. We adjusted for age, DXA machine, race, menopausal symptoms, education, smoking, physical activity, body mass index, alcohol use, physical function, and sleep medication use. In adjusted linear regression models, women who reported sleeping 5 hours or less per night had on average 0.012 to 0.018 g/cm² significantly lower BMD at all four sites compared with women who reported sleeping 7 hours per night (reference). In adjusted multinomial models, women reporting 5 hours or less per night had higher odds of low bone mass and osteoporosis of the hip (odds ratio [OR] = 1.22; 95% confidence interval [CI] 1.03-1.45, and 1.63; 1.15-2.31, respectively). We observed a similar pattern for spine BMD, where women with 5 hours or less per night had higher odds of osteoporosis (adjusted OR = 1.28; 95% CI 1.02-1.60). Associations of sleep quality and DXA BMD failed to reach statistical significance. Short sleep duration was associated with lower BMD and higher risk of osteoporosis. Longitudinal studies are needed to confirm the cross-sectional effects of sleep duration on bone health and explore associated mechanisms. © 2019 American Society for Bone and Mineral Research.

Association between objective sleep duration and bone mineral density in older postmenopausal women from the Study of Osteoporotic Fractures (SOF)

Methodological limitations preclude determination of the association between sleep duration and bone mineral density (BMD) from existing literature. This was the first study to use objective sleep duration to determine its association with BMD. Nocturnal sleep duration, assessed objectively (actigraphy) or subjectively (questionnaire), was not independently associated with BMD in postmenopausal women.

INTRODUCTION

Both long and short self-reported sleep durations are associated with low bone mineral density (BMD) in men and women. The association between sleep duration measured by actigraphy and BMD in postmenopausal women is unknown.

METHODS

The Study of Osteoporotic Fractures (SOF) ancillary sleep study was used to determine the association between sleep duration and BMD at the total hip and femoral neck in postmenopausal women ≥ 75 years old. Sleep duration was assessed by wrist actigraphy (average 4 nights) and questionnaire. BMD was compared between postmenopausal women with short (< 6 h/night) vs. NIH-recommended (7-8 h/night) sleep durations. Data were analyzed using a 2-sample t test (unadjusted) and multivariate regression model (adjusted). Simple linear regression was used to estimate the difference in BMD per additional hour of sleep when sleep duration was considered as a continuous, rather than dichotomized, variable.

RESULTS

Total hip BMD was higher in women with actigraphically assessed shorter sleep duration in unadjusted models only. No clinically or statistically significant differences in total hip or femoral neck BMD were observed according to nocturnal sleep duration after adjusting for body mass index (BMI) in dichotomized (N = 874) or continuous (N = 1624) sleep duration models or when subjective sleep duration was used. When sleep duration included daytime naps, longer sleep duration was associated with lower total hip BMD (β = - 0.005, p = 0.04).

CONCLUSIONS

Nocturnal sleep duration, whether assessed objectively (actigraphy) or subjectively (questionnaire), was not independently associated with BMD in older postmenopausal women.

Association between Sleep Quality and Body Composition in Sedentary Middle-Aged Adults

Background: Ageing is associated with sleep pattern changes and body composition changes, which are related to several diseases. Purpose: This study aimed to analyse the association between sleep quality and an extensive set of body composition parameters (waist-hip ratio, body mass index, bone mineral content, bone mineral density, lean mass, lean mass index, fat mass, fat mass percentage, fat mass index, visceral adipose tissue) and sleep quality in sedentary middle-aged adults. We also aimed to evaluate whether the possible associations accord between subjective and objective measurements of sleep quality. Methods: 74 (39 women) middle-aged sedentary adults (40–65 years old) participated in the present study. The sleep quality was assessed using the Pittsburgh sleep quality index (PSQI) scale and accelerometers. A PSQI global score more than 5 indicates poor sleep quality. Weight, height, waist and hip circumferences were measured, and body mass index and waist-hip ratio were also calculated. Body composition was assessed with a dual-energy X-ray absorptiometry scanner. Results: The PSQI global score was negatively associated with bone mineral content, bone mineral density, lean mass, lean mass index and positively associated with fat mass percentage. No association was found between accelerometer parameters and body composition variables. Conclusion: We showed that a subjective poor sleep quality was negatively associated with bone mineral content (BMC), bone mineral density (BMD), lean mass and lean mass index (LMI) whereas was positively associated with fat mass percentage in middle-aged adults. We also observed that these associations did not accord with objective sleep quality measurements.

Association between sleep quality and bone mineral density in Chinese women vary by age and menopausal status

OBJECTIVE

Sleep quality is closely related to bone health. Aging and estrogen deficiency are known determinants of poor sleep quality and osteoporosis. However, the impact of aging and menopause on the associations between sleep quality and bone mineral density (BMD) remains unclear. This study aimed to examine the association between sleep quality and BMD in Chinese women vary by age groups and menopausal status.

METHODS

A total of 2067 women aged 18-80 years were included. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI) and the score >7 was indicative of poor sleep quality. BMD was determined using the dual-energy X-ray absorptiometry. Participants were categorized into three age groups. Multiple linear regression models were conducted to evaluate the associations between sleep quality and BMD. Covariates included in the models were age, menopausal status, weight, height, percent body fat, physical activity, alcohol drinking, calcium supplement use, marital status, education and metabolic diseases.

RESULTS

We observed that poor sleep quality was correlated to low total BMD and legs BMD in middle-aged women after adjusting for potential confounders. Furthermore, when we reran the regression models based on menopausal status in middle-aged women, significant associations between BMD and sleep quality were observed in premenopausal and early postmenopausal groups.

CONCLUSION

Our findings showed a more robust association between sleep quality and BMD in premenopausal and early menopausal groups. Further studies should be conducted to explore whether sleep quality intervention would improve bone health of women in these periods and prevent osteoporosis in their late life.

Sleep onset latency is related with reduced bone mineral density in elderly people with insomnia: a retrospective study

Purpose

Inconsistent outcome about association between insufficient sleep and bone mineral density (BMD) has been reported. The present study aimed to determine whether BMD was associated with score of Pittsburgh Sleep Quality Index (PSQI).

Methods

A total of 410 patients (mean age 81.6±5.9 years) attending our hospital for evaluation of sleep were retrospectively studied. Dual-Energy X-ray Absorptiometry was used to measure BMD and T-score at femoral neck and lumbar spines over L2–L4 regions. Subjective sleep status was evaluated by the PSQI questionnaires. The Mann–Whitney U test and chi-square analysis were used to compare continuous variables and categorical variables, respectively. Spearman correlation test was conducted to find the relationship between BMD and other clinical factors. Multinomial logistic regressions analysis was performed to analyze independent factors predicting BMD.

Results

Majority of the participants with osteoporosis (OP) were female and had lower body mass index (BMI) and higher sleep onset latency score. Spearman correlation test showed that gender, BMI, score of total PSQI, and sleep onset latency were significantly related to BMD and T-score in femoral neck and lumbar region L2–L4. Finally, multinomial logistic regression analysis demonstrated that gender and age were independent factors for OP and osteopenia and that after adjustment for gender, age, and BMI, sleep onset latency of <15 minutes (OR: 0.38; 95% CI: 0.15–0.96; P=0.04) and 16–30 minutes (OR: 0.37; 95% CI: 0.17–0.79; P=0.01) were less likely to have reduced BMD.

Conclusion

There was a significant association between BMD and sleep onset latency, suggesting that, in elderly patients with sleep problem, BMD measurement and intervention for OP might be valuable.

Sleep duration and the risk of osteoporosis among middle-aged and elderly adults: a dose-response meta-analysis

It remains unclear how many hours of sleep are associated with the lowest risk of osteoporosis. This meta-analysis was performed to assess the dose-response relationship between sleep duration and risk of osteoporosis. PubMed and Web of Science were searched from inception to December 3, 2017, supplemented by manual searches of the bibliographies of retrieved articles. Data were pooled using fixed- and random-effects models. Restricted cubic spline analysis with four knots was used to model the sleep duration and osteoporosis association. Four cross-sectional studies with eight records were eligible for inclusion in the meta-analysis. A U-shaped dose-response relationship was observed between sleep duration and risk of osteoporosis, with the lowest risk observed at a sleep duration category of 8-9 h per day. Compared with 8-h sleep duration per day, the pooled odds ratio for osteoporosis were 1.03 (95% CI 1.01-1.06) for each 1-h reduction among individuals with shorter sleep duration and 1.01 (95% CI 1.00-1.02) for each 1-h increment among individuals with longer sleep duration. Our dose-response meta-analysis shows a U-shaped relationship between sleep duration and risk of osteoporosis, with the lowest osteoporosis risk at about 8 h per day of sleep duration. Both short and long sleep duration is associated with a significantly increased risk of osteoporosis in the middle-aged and elderly adults, appropriate sleep duration could help for delay or prevention of osteoporosis.

The importance of the circadian system & sleep for bone health

Adequate sleep timed appropriately during the circadian night is important for numerous biological processes and systems. New evidence suggests that both sleep timing and duration may be important for optimal bone health as well. This review examines the diurnal variation of bone turnover markers (BTMs) and the importance of circadian clock genes in regulating bone mass. In addition, this review explores the evidence for a link between shift work (and its associated disturbances in sleep duration/quality and circadian alignment) and alterations in bone metabolism and bone health. Finally, we review how commonly used medications and over-the-counter substances (e.g. caffeine, melatonin) complicate the relationship between sleep and circadian disorders and bone health.

Bone Turnover Markers After Sleep Restriction and Circadian Disruption: A Mechanism for Sleep-Related Bone Loss in Humans

CONTEXT

Sleep abnormalities are associated with low bone mineral density. Underlying mechanisms are unknown.

OBJECTIVE

Investigate the impact of sleep restriction with circadian disruption on bone biomarkers.

DESIGN

Intervention study.

PARTICIPANTS AND METHODS

Four bone biomarkers [C-terminal cross-linked telopeptide of type I collagen (CTX) = bone resorption, N-terminal propeptide of type I procollagen (P1NP) = bone formation, sclerostin and fibroblast growth factor 23 = osteocyte function] were measured in bihourly serum samples over 24 hours at baseline and after ∼3 weeks of sleep restriction (5.6 hours sleep/24 hours) with concurrent circadian disruption (recurring 28-hour "day" in dim light) in 10 men (age groups: 20 to 27 years, n = 6; 55 to 65 years, n = 4). The effects of sleep/circadian disruption and age on bone biomarker levels were evaluated using maximum likelihood estimation in a mixed model for repeated measures.

RESULTS

P1NP levels were lower after intervention compared with baseline (P < 0.001); the decrease in P1NP was greater for younger compared with older men (28.0% vs 18.2%, P < 0.001). There was no change in CTX (Δ = 0.03 ± 0.02 ng/mL, P = 0.10). Sclerostin levels were higher postintervention in the younger men only (Δ = 22.9% or 5.64 ± 1.10 pmol/L, P < 0.001).

CONCLUSIONS

These data suggest that 3 weeks of circadian disruption with concurrent sleep restriction can lead to an uncoupling of bone turnover wherein bone formation is decreased but bone resorption is unchanged. Circadian disruption and sleep restriction may be most detrimental to bone in early adulthood.

Association between loss of bone mass due to short sleep and leptin-sympathetic nervous system activity

BACKGROUND

Sleep has been reported to be an important factor in bone metabolism, and sympathetic nervous system activity has been reported to regulate bone metabolism. In this study, we evaluated the association between sleep, sympathetic nervous system activity, and bone mass.

METHODS

The study subjects were 221 individuals (108 males; 113 females; mean age: 55.1±7.0years) divided into two groups: those who slept for less than 6h a day (short sleep [SS] group), and those who slept 6h or longer (normal sleep [NS] group). The groups were compared with regard to lifestyle, cortical bone thickness, cancellous bone density, bone metabolism markers, blood leptin levels, and sympathetic nervous system activity as evaluated by heart rate variability analysis.

RESULTS

Significant differences were observed between the two groups in cortical bone thickness, blood TRACP-5b, and leptin levels. The L/H ratio (an index of sympathetic nervous system activity) was higher in the SS group than in the NS group. Significant negative correlations were observed between cortical bone thickness and both the L/H ratio and leptin levels, and a significant positive correlation was observed between the L/H ratio and leptin levels.

CONCLUSIONS

Short sleep was associated with a decline in cortical bone thickness due to the promotion of bone resorption and sympathetic nervous system hyperactivity in the middle-aged group. Leptin levels and cortical bone thickness were found to be closely related, suggesting that cortical bone mass may be regulated via interaction with the leptin-sympathetic nervous system.