Pain is temporary, but a pain relief pill could have detrimental effects on the brain.

Around 42% of Americans will experience dementia after the age of 55 — nearly the same amount of older adults with arthritis.

But while many turn to a popular supplement to ease joint pain, new research suggests they could actually speed up cognitive decline as well as increase the chances of death in those with Alzheimer’s.

More than 40 million Americans take glucosamine — composed of glucose and the amino acid glutamine — each year to slow the breakdown of cartilage in the joints, which may relieve pain and swelling.

A study published in Nature Metabolism, though, found that people with Alzheimer’s who took glucosamine supplements were 25% more likely to die within five years than those who didn’t.

The widely used supplement also affected those with mild cognitive impairment, or the early stages of dementia, and they were more likely to progress to full Alzheimer’s.

The researchers also found that mice with Alzheimer’s-like symptoms who were given glucosamine ended up with worse memory.

On the other hand, blocking the enzyme that makes sugars like glucosamine actually improved dementia symptoms like short-term memory loss.

A hallmark of Alzheimer’s is the accumulation of toxic protein clumps in the brain, known as tau, that interfere with cognitive function.

However, another lesser-known issue with the degenerative disease is the extra sugar coating brain cells and proteins that build up.

Healthy brain cells normally carry short chains of sugars called N-glycans that help proteins attach to each other.

In those with Alzheimer’s, the chains pile up in places they shouldn’t.

This causes proteins in the brain to not work properly, causing memory issues and cells to die, a condition called hyperglycosylation.

Earlier research has shown that regular glucosamine use is linked to lower dementia risk, but this was in adults with healthy cognitive function.

Since the findings of the most recent study were based on patient records, they only show an association between cognitive decline and use of glucosamine supplements.

The research team is also unsure of whether the effects of glucosamine on cognitive health are dependent on dose, brand of supplement or how long people take it.

Currently, researchers are exploring compounds that block the N-glycan molecule and reduce the buildup of sugars on brain cells to see the effects on Alzheimer’s progression.

And while not in supplement form, several studies have also suggested that a diet rich in sugar and saturated fat can contribute to inflammation in the brain, potentially damaging brain cells and raising the risk of dementia.