Alzheimer's disease may show early signs decades before memory loss

Recent scientific findings suggest that Alzheimer's disease may involve biological changes that occur decades before memory loss becomes apparent. Research indicates that processes linked to the disease can begin 15 to 20 years before a formal diagnosis.

Early warning signs may not be cognitive. Instead, they can manifest as changes in mood, sleep disturbances, a diminished sense of smell, or physical changes such as a weakening grip strength. Timothy Chang, an associate professor of neurology at the University of California, Los Angeles, notes that individuals may exhibit various non-cognitive symptoms while the brain undergoes changes like the accumulation of abnormally folded proteins.

New research also highlights a shift in the brain's immune system. Studies of the hippocampus suggest that around age 50, the original microglia—cells responsible for maintaining a healthy brain environment—begin to decline. They are increasingly replaced by cells with higher inflammatory activity, similar to monocytes found in the blood. This shift toward a chronic inflammatory state in the brain is believed to be a key factor in the development of Alzheimer's.