Cognitive Decline is Associated with an Accelerated Rate of Bone Loss and Increased Fracture Risk in Women
by The American Society for Bone and Mineral Research:
Cognitive decline and osteoporosis often coexist and some evidence suggests a causal link. However, there are no data on the longitudinal relationship between cognitive decline, bone loss and fracture risk, independent of aging. This study aimed to determine the association between (i) cognitive decline and bone loss; and (ii) clinically significant cognitive decline (≥3 points) on Mini Mental State Examination (MMSE) over the first 5 years and subsequent fracture risk over the following 10 years.
A total of 1741 women and 620 men aged ≥65 years from the population-based Canadian Multicentre Osteoporosis Study were followed from 1997 to 2013. Association between cognitive decline and (i) bone loss was estimated using mixed-effects models; and (ii) fracture risk was estimated using adjusted Cox models.Over 95% of participants had normal cognition at baseline (MMSE ≥ 24).
The annual % change in MMSE was similar for both genders (women −0.33, interquartile range [IQR] −0.70 to +0.00; and men −0.34, IQR: −0.99 to 0.01). After multivariable adjustment, cognitive decline was associated with bone loss in women (6.5%; 95% confidence interval [CI], 3.2% to 9.9% for each percent decline in MMSE from baseline) but not men.
Approximately 13% of participants experienced significant cognitive decline by year 5. In women, fracture risk was increased significantly (multivariable hazard ratio [HR], 1.61; 95% CI, 1.11 to 2.34).
There were too few men to analyze.There was a significant association between cognitive decline and both bone loss and fracture risk, independent of aging, in women. Further studies are needed to determine mechanisms that link these common conditions.In summary, this study indicated that in women the rate of cognitive decline was significantly associated with bone loss, independent of age, education, comorbidities, and lifestyle factors.
Notably, the relationship between bone loss and cognitive decline was bidirectional with no evidence of one preceding the other. Furthermore, a significant cognitive decline over 5 years was associated with an increased risk not only of hip and vertebral but also NHNV fractures over the subsequent 10 years.
Importantly, fracture risk appeared to be only partly mediated by the concomitant increased rate of bone loss. Men, similar to women, experienced significant cognitive decline and bone loss during the study follow-up. However, the sample size was too small to accurately ascertain the relationship between the trajectories of bone mass and cognitive function.
These studies suggest that the relationship between bone loss, cognitive decline and fracture risk in women is driven by shared risk factors. Further mechanistic pathways are needed to understand the complex relationship between osteoporosis and dementia and the contributors of fracture risk in cognitively impaired people. This study failed to demonstrate a relationship between cognitive decline and bone loss in the relatively small cohort of men Thus, further studies, involving larger cohorts of men are needed to confirm or refute any association.