Can repeated CT scans increase dementia risk from radiation?
CT scans use X-rays, a type of radiation that passes through the body to create detailed images of organs and bones. Each scan delivers a dose of ionizing radiation, which can damage DNA in cells if exposure builds up over time. A single chest CT might give about 7 millisieverts of radiation, similar to years of natural background exposure from the earth and air. Head CT scans, common for checking injuries or strokes, also carry this risk.
Doctors order CT scans often because they are quick, widely available, and cheaper than alternatives like MRI, which uses magnets and radio waves with no radiation. In 2023 alone, over 93 million CT scans happened in the US, mostly on adults. This high number raises concerns about total radiation from repeats, especially for people getting multiple scans for ongoing issues like heart problems or follow-up checks.
The main proven risk from repeated CT radiation is a small increase in cancer odds later in life. Studies link CT scans to about 5 percent of new cancers each year, including lung, colon, leukemia, breast, and thyroid types. Children face higher risks from the same doses because their cells divide faster. But what about the brain and dementia?
Dementia involves brain changes like shrinking tissue, plaques, or poor blood flow, seen in conditions such as Alzheimer’s. CT scans can spot some brain issues, like hidden strokes or white matter damage, which tie to higher fall risks and sometimes dementia progression. Radiation itself might harm brain cells too. High radiation doses can cause inflammation or cell death in the brain, similar to effects seen after cancer radiation therapy. Animal studies show brain radiation leading to memory problems, but human data on low CT doses is less clear.
No large study directly proves repeated CT scans cause dementia. Cancer risk gets more attention because models predict it better from radiation data. For dementia, risks might come indirectly: radiation could speed up vessel damage or protein buildup in the brain, mimicking aging effects. Older adults, already at dementia risk, get many CTs in emergencies, adding exposure when brains are vulnerable. One analysis warns that cumulative doses from repeats could contribute to cognitive decline, though proof is not firm.
To lower risks, doctors now use lower-dose CT techniques and consider MRI first for brains, as it shows soft tissues better without radiation. Patients can ask about necessity: Is this scan vital now, or can we wait or try ultrasound? Tracking personal scan history helps avoid extras.
Sources
https://www.auntminnie.com/clinical-news/mri/article/15749584/ct-mri-reveal-hidden-brain-changes-linked-to-increased-fall-risk
https://www.consultant360.com/story/catheterizations-ct-scans-magnify-radiation-exposure-kids-heart-disease
https://pubs.rsna.org/doi/abs/10.1148/rg.2020190070
https://ezra.com/en-gb/blog/brain-scan
https://wholehealthchicago.com/blog/2025/12/22/think-twice-before-you-agree-to-your-next-ct-scan
https://www.auntminnie.com/clinical-news/molecular-imaging/article/15774398/brain-imaging-billing-radiation-exposure-top-2025s-mostread-list
https://www.bangkokhospital.com/en/bangkok-bone-brain/content/3m-memory-moving-multiple_sclerosis
