Cognitive dysfunction and poor bone health are more prevalent in older individuals than in younger ones. Clinically both conditions share common risk outcomes, including falls, loss of muscle function, balance disorders, gait abnormalities and death. These two major health problems are increasingly common, significantly impacting the quality of life of the elderly.1

Emerging evidence highlights a potential link between cognitive functions and bone health, further underscoring the need to address these interconnected challenges. Animal studies have revealed that bone remodeling is directly controlled by the central nervous system, which mediates bone homeostasis through the hypothalamus via the neural and neurohumoral pathways.2 In the neural pathway, the hypothalamus controls bone remodeling through increased output of sympathetic stimulation mediated by leptin, an antiosteogenic hormone.3 The neurohumoral pathway involves hypoythalamic control of bone formation through growth hormone (GH) and insulin-like growth factor-1 (IGF-1), which are secreted by anterior lobe of pituitary gland.4 Moreover, growth hormone (GH) acts synergistically with insulin-like growth factor-1 (IGF-1) to maintain bone homeostasis.5

Although a potential relationship between cognitive function and bone mineral density (BMD) has been suggested, findings from related human studies remain controversial. For instance, Kipen et al. found no significant association between BMD and mild dementia,6 while another study similarly concluded that no relationship exists between cognitive impairment and BMD.7 However, some human studies have suggested that individuals with higher BMD have better cognitive performance.8 Apart from the controversial evidence, some studies have shown that BMD is associated with certain domain of cognitive functions. Studies have shown that women with higher BMD perform better on verbal memory tests than on visual memory tests.9 Another study suggested that women with osteoporosis have poorer cognitive assessment score on Digit Symbol test and a higher risk of cognitive deterioration.10 Cognitive functions encompass various domains, including sensation and perception, motor skills, complex attention, memory, executive functioning, processing speed and verbal skills. However, the specific domains of cognitive function that are related to bone health, as well as those that are not, remain poorly understood.

This study examined the relationship between cognitive functions (assessed by the Digit Symbol Substitution Test [DSST], the Consortium to Establish a Registry for Alzheimer’s Disease [CERAD] Word Learning sub-test and the Animal Fluency test) and BMD, osteoporosis, and osteopenia in the elderly. These tests measure different domains of cognitive functions. DSST is a multifactorial test that measures most executive brain functions, including visuoperceptual, oculomotor, attention and motor activity. In contrast, the CERAD test measures verbal/episodic memory and the Animal Fluency test assess semantic memory of an individual. This study may help resolve the controversial findings regarding the association between cognitive functions and bone health.