Increased evening cortisol levels have been implicated in bone mineral density (BMD) loss. The effect on bone microarchitecture and fracture risk has never been studied.
To study the relationship between salivary cortisol circadian rhythm and (1) trabecular bone score (TBS) and (2) fracture prevalence.
Cross-sectional study including 608 women >50 years old (mean = 65.5) from the OsteoLaus cohort. Data included the FRAX© questionnaire, BMD, TBS and vertebral fracture (VFx) assessment by dual X-ray absorptiometry, and measures of salivary cortisol (awakening, 30 minutes thereafter, 11 am, and 8 pm).
In the multivariate model, participants in the highest tertile of 8 pm salivary cortisol (sc-8 pm) (mean = 5.7 ± 2.5 nmol/L) vs lowest tertile (1.7 ± 0.4 nmol/L) had lower TBS values (1.27 vs 1.29; P = 0.02), more prevalent VFx grades 2 and 3 (odds ratio = 5.34; P = 0.012), low-trauma fractures (odds ratio = 1.80; P = 0.036), and major osteoporotic fractures (odds ratio = 1.96; P = 0.042), without difference in lumbar spine BMD (0.91 vs 0.92 g/cm2; P = 0.431). VFx prevalence was associated with sc-8 pm and TBS independently of each other and of other risk factors. The cut-point for sc-8 pm correlating with the presence of >1 VFx was 3.62 nmol/L (sensitivity 0.74, specificity 0.66).
High sc-8 pm is associated with low TBS and an increased prevalence of radiologic VFx independently of other risk factors. Measurement of sc-8 pm may add relevant information in the assessment of fracture risk.