In the villages of rural India and the bustling lanes of its cities, a silent epidemic is unfolding—one that begins in the mouth and may end in the mind.

A sweeping new study of nearly 57,000 middle-aged and older Indians has uncovered a troubling link between poor oral health and cognitive decline. The researchers, drawing from the Longitudinal Aging Study in India (LASI), found that people who had lost all their natural teeth scored significantly lower on cognitive tests than those who retained them. Even those missing just some teeth showed a noticeable decline.

The mouth-mind link

Researchers have long speculated that what happens in the mouth might affect the brain. Past studies, mostly from high-income countries, have suggested that tooth loss may impair memory, orientation, and executive function. Some have even found that gum disease and its bacteria might inflame the brain, potentially accelerating Alzheimer’s.

This new Indian study confirms many of those fears.

Using a battery of cognitive tests, the team measured memory, orientation, math ability, object naming, and spatial function in participants aged 45 and older. People who had lost all their teeth scored, on average, 0.65 points lower on a 42-point cognitive scale—even after adjusting for other health and social factors. That’s a small but statistically significant drop.

It’s not clear exactly why this happens, but it could be linked to chewing. Missing teeth reduce chewing ability, which affects digestion and nutrient absorption—especially of key brain-supporting vitamins like iron and vitamin D. Tooth loss also lowers sensory feedback from the jaw to the brain, and that might dull mental function over time.

Another pathway may involve inflammation. Gum disease is an inflammatory condition, and chronic inflammation is now widely accepted as a contributor to dementia and other neurodegenerative diseases.

Moreover, people with missing teeth may eat fewer fruits, vegetables, and proteins—foods essential for cognitive resilience.

Some surprising findings

Yet not all the study’s results were predictable.

Strangely, people who reported three or more active oral health issues—like painful teeth, bleeding gums, or mouth ulcers—actually scored slightly better on cognitive tests. That association held even after adjusting for income, education, depression, and chronic illness.

The researchers are cautious about this result as it’s not clear why this is happening.

It’s possible that these problems, while unpleasant, weren’t severe enough to disrupt chewing or nutrition. Painful gums may sting, but they don’t necessarily stop someone from eating. Missing teeth, on the other hand, do.

But what is clear is that this offers yet another reason to take care of your teeth.

“This study adds to growing evidence that the mouth is not separate from the rest of the body. Even a small dip in cognitive scores, when seen across a large population, can point to a serious public health issue. It reminds us that good oral hygiene isn’t just about teeth—it’s about brain health too,” says Dr. Madelyne Salo, who was not involved in this study.

India’s oral health system is underfunded and fragmented. Billions of people worldwide find themselves in a similar situation. Cultural attitudes often dismiss tooth loss as a normal part of aging. And public health campaigns rarely emphasize dental hygiene, let alone link it to brain health. Furthermore, the increase in sugar consumption puts even more pressure on our oral health. We’re eating too much sugar and that’s not just bad for our mouth, it’s bad for our brain too.

The cost of inaction may be steep. Cognitive decline not only burdens families but also erodes productivity and stretches healthcare systems. With dementia care expected to surpass $2 trillion globally by 2030, prevention is no longer optional.

The study was published in Nature Scientific Reports.