Scientists say the brain’s Alzheimer’s 'clock' may start ticking faster at this age

Over the years, scientists have theorized about the gradual progression of Alzheimer's disease. A study that was recently published by the Mayo Clinic Study in Alzheimer's & Dementia points to late midlife — around the late 60s — as a key phase when the brain’s Alzheimer’s-related changes begin accelerating. Published on April 29, the study analyzed the brain health of 2,082 participants from Olmsted County, Minnesota, to determine that the brain’s “Alzheimer’s clock” picks up pace around the ages of 68 to 71.

Protein in blood can hint at Alzheimer's damage

Participants were asked to give their blood samples after a night of fasting. The researchers then tested the proteins related to Alzheimer's damage, which include proteins connected to amyloid plaques, tangled nerve fibers, brain inflammation, and nerve cell injuries. On the other hand, a smaller group of 462 participants was also taken and tested under a highly precise lab method to verify the results. A few others also underwent brain imaging and cognitive tests that checked their memory, decision-making skills, language, and spatial reasoning.

What researchers discovered

The results showed a clear pattern across participants, with changes unfolding gradually over time. Thinking ability began to decline around age 60, followed by a rise in amyloid plaques— protein buildups in the brain that are one of the earliest signs of Alzheimer’s — at 62. Tau-related changes, which refer to twisted protein fibers that disrupt communication between brain cells, increased by around 67. By 68, signs of brain inflammation grew, and the hippocampus, the part of the brain linked to memory, began to shrink. Markers of nerve cell damage showed a sharper rise later, around age 71, completing the overall progression observed in the study.

The smaller group had two tau-related markers that showed changes around the age of 73. The Tau PET scans did not show a clear breaking point, but the researchers suspected this was due to the small number of participants, which made it difficult to see changes. The results matched what scientists have been theorizing all these years about the progression of Alzheimer's. It started with amyloid accumulation, followed by tau, and lastly, the nerve cells were damaged.

How does 'normal' aging work?

Mayo Clinic studied the general population to understand the issue under "normal aging," instead of studying people who were already suspected of having Alzheimer's. Out of the 2,082 participants, the median age was 71 years old, and the majority of the people were male (54%). The study showed that 87% of the participants had normal thinking abilities, 11% had mild memory problems, and only 1% were diagnosed with dementia.

The findings also align with earlier research published in the New England Journal of Medicine, which showed that Alzheimer’s-related changes can begin 15 to 20 years before symptoms appear, with memory decline starting roughly a decade before diagnosis. Together, the studies suggest that while the disease develops silently for years, its progression becomes more noticeable as people approach their late 60s. 

However, the study does have a few limitations: It was conducted at a single point in time, and the same people were not studied over several years, making it inconsistent. The people who were studied were all from Minnesota, which means it may not apply to people from other parts of the country or the world. Nonetheless, it is a great progress in studying and understanding Alzheimer's disease. 

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