A growing body of research highlights the critical role bones play not only in physical support but also in brain health, particularly as people age. This connection, known as the bone-brain axis, suggests that maintaining healthy bones may be integral to preserving cognitive function in older adults.

The concept that bones influence more than just structural stability dates back to the 19th century when French pathologist Jean-Martin Charcot observed neurological damage linked to bone and joint deterioration in patients with tabes dorsalis, a complication of untreated syphilis. Although his contemporaries initially rejected his ideas, recent scientific advances have given credence to Charcot’s early insights.

In the early 2000s, bones were reclassified as endocrine organs capable of producing hormones, notably osteocalcin, which is secreted by osteoblasts—the cells responsible for bone formation. Osteocalcin does not remain confined to the skeleton; it enters the bloodstream, crosses the blood-brain barrier, and interacts with neurons in key brain areas such as the brainstem and hippocampus. This hormone has been found to regulate blood glucose, influence testosterone and cortisol levels, support muscle function during exercise, and importantly, contribute to memory and anxiety regulation.

Research led by Dr. Gérard Karsenty at Columbia University has demonstrated that osteocalcin plays a vital role throughout life, including in prenatal brain development. Osteocalcin produced by the mother crosses the placenta to aid in forming the hippocampus and promoting spatial learning and memory in the fetus.

In animal studies, aged mice exhibiting memory decline show marked improvement following osteocalcin supplementation, suggesting a direct link between the hormone and cognitive performance. Conversely, reduced osteocalcin levels are associated with hippocampal shrinkage and damage to the corpus callosum, which connects the brain's hemispheres. Mice lacking osteocalcin also exhibit increased anxiety and reduced levels of key neurotransmitters such as serotonin, dopamine, and norepinephrine.

Osteocalcin levels naturally decline with age, typically beginning before 30 in women and 50 in men, paralleling declines in bone density and cognitive function. Exercise emerges as a principal stimulant for osteocalcin release: mechanical loading of bones through weight-bearing and resistance activities prompts osteoblasts to enhance bone strength and secrete osteocalcin. In contrast, low-impact activities like swimming do not provide sufficient mechanical stress to stimulate this response.

Clinical studies indicate that regular weight-bearing exercise—such as brisk walking, running, or resistance training—can increase osteocalcin levels and improve bone mineral density in older adults, particularly postmenopausal women with osteoporosis. Adequate dietary intake of nutrients like vitamin D and K2 also supports bone and hormonal health.

While the translation of findings from animal models to human cognition requires further research, and studies of osteocalcin in conditions like Alzheimer’s disease have yielded mixed results, the evidence underscores the importance of maintaining bone health.

Experts emphasize that preserving the bone-brain axis is crucial for aging populations. Staying physically active not only reduces the risk of falls and fractures but may also sustain the hormonal signals that support brain function, helping older adults maintain their cognitive vitality.