Loss of Smell May Signal Alzheimer's Years Before Symptoms Appear, Study Finds
New research published in April 2026 found that immune cells in the brain destroy smell-related nerve fibers in the early stages of Alzheimer's disease, suggesting that loss of smell could serve as an early warning sign years before cognitive symptoms emerge.
Scientists have found that losing the sense of smell may signal Alzheimer's disease years before memory loss and other cognitive symptoms appear.
The research, published in April 2026, found that immune cells in the brain destroy smell-related nerve fibers during the early stages of Alzheimer's. The damage occurs before the disease progresses to the regions of the brain responsible for memory and thinking.
Researchers said the findings could lead to new screening tools. A simple smell test might one day help doctors identify people at risk of Alzheimer's early enough to intervene with preventive treatments.
Alzheimer's affects more than 6 million Americans and is the most common cause of dementia. Current diagnostic tools, including brain scans and spinal fluid tests, are expensive and not widely available. A low-cost smell test could make early detection more accessible.
Separate research published this month found that Alzheimer's is a complex mix of biology, aging, and overall health, which is why drugs targeting a single factor have often fallen short. Scientists are calling for more research into combination approaches.
Vitamin D levels in midlife were also found to play a significant role in long-term brain health. Adults with lower vitamin D levels in their 40s and 50s showed higher rates of cognitive decline later in life.
Loneliness may affect memory in older adults, but researchers said it does not necessarily speed up mental decline, according to another study published in April.
