Is Low Bone Density Linked to Faster Brain Aging?

Is low bone density linked to faster brain aging?

Yes, in this study. Older adults with lower spine bone density lost thinking ability faster and built up more white matter damage in certain brain areas over time. The link was modest, it showed up on an ordinary chest CT scan, and it was stronger in people with diabetes.

Researchers followed 715 adults from the Multi-Ethnic Study of Atherosclerosis, a long-running research study. The median age was 69, and the middle half of the group was between 65 and 75. There were 397 men and 318 women, and none had known heart disease when the study began. Each person had a chest CT scan without contrast dye. A validated artificial intelligence program read those scans and measured the bone density of the spine bones in the chest. The same people then had repeated brain MRI scans and memory and thinking tests.

White matter is the brain’s wiring. It carries signals between different regions. As we age, that wiring can fray, and small bright spots called white matter lesions appear on MRI. Both changes are markers of brain aging. The question was whether weak bones go along with fraying brain wiring and falling test scores.

What the data show

The clearest signal was in thinking ability. Lower bone density was linked to a faster drop in a combined score of memory and thinking tests, measured in 639 people. The odds that this was pure coincidence were about 1 in 500 (P = .002). A second screening test of mental function, given to 675 people, showed the same pattern, with less than a 1 in 1,000 chance of coincidence (P < .001).

The brain scans told a similar but weaker story. Lower bone density was tied to faster buildup of white matter lesions in the corpus callosum, the thick bridge of fibers that joins the left and right halves of the brain. In the study’s model, that buildup ran 12.8% per year faster (408 people, adjusted P = .04). Wiring quality also declined faster in the internal capsule, a busy highway for signals between the brain and body (adjusted P = .006).

Across the whole brain, lower bone density was linked to faster wiring decline at first. That result did not hold up once the researchers corrected for testing many brain areas at once. Diabetes made the link with lesion growth stronger (P = .03).

Dr. Kumar’s Take

This study does not show that thin bones damage the brain. It is an observational study, so it can only show that the two tend to move together. The researchers adjusted for demographics, a gene variant called APOE-ε4 that is tied to Alzheimer’s disease, heart and metabolic risk factors, lifestyle, and medications. Even so, something else could still sit behind both problems.

The practical angle is more interesting to me. Plenty of people already have chest CT scans for other reasons, and those images include the spine. If a computer can pull bone density out of a scan that was done for another reason, that is free data. The authors suggest it may help flag people whose brains are aging faster than expected.

The effects were modest. This is a signal worth watching, not a reason for alarm if your bone density is low.

How strong is the evidence?

The study has real strengths. It followed people over time rather than taking a single snapshot. It used detailed MRI methods that look at the quality of brain wiring, not just its size. It also drew from a multi-ethnic group, which makes the findings more relevant to a broad population.

There are limits too. Each analysis included fewer than the full 715 people, between 405 and 675 depending on the measure. The whole-brain wiring result lost its strength after correction for multiple comparisons, so the brain findings are regional, not global. And because people with known heart disease were left out, the results may not apply to them.

Practical Takeaways

Treat low bone density as a whole-body health signal, not just a fracture risk, since in this study it tracked with faster decline in thinking ability.
If you have diabetes, keep blood sugar under good control, because diabetes strengthened the link between low bone density and brain lesion growth here.
If you have had a chest CT scan, ask your doctor whether it showed anything about your spine bones, since the spine shows up on those images.
Do not read low bone density as a dementia diagnosis, because this study only showed a modest link, not cause and effect.

FAQs

Can a regular chest CT scan measure bone density?

In this study, yes. A validated artificial intelligence program measured bone density in the spine bones of the chest from CT scans taken without contrast dye. That is a different route from a dedicated bone density test. The authors suggest this could help detect faster brain aging from a scan that was already done. Ask your doctor what your own scan report does and does not include.

Does osteoporosis cause dementia?

This study cannot answer that. It found that lower bone density went along with faster decline in thinking and more white matter damage, but it was observational. Bone and brain may simply share risk factors that age them both. Only a study that tests whether protecting bone also protects the brain could show cause and effect.

What are white matter lesions?

They are small areas of damage in the brain’s wiring that show up as bright spots on certain MRI scans. They become more common with age. Researchers treat them as a marker of brain aging. In this study, they grew faster in the corpus callosum among people with lower bone density.

Bottom Line

In 715 older adults without known heart disease, lower spine bone density measured by AI on a routine chest CT was linked to faster decline in thinking ability and faster white matter damage in specific brain regions, especially in people with diabetes. The effect was modest and the study cannot prove cause and effect. Still, it suggests that scans people already get could offer an early clue about how fast the brain is aging.

Read the full study