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Teeth health and brain volume may be closely linked, according to new research. Malquerida Studio/Stocksy
  • The loss of teeth and gum disease may be associated with a reduction in brain volume that reflects the atrophy of brain tissue, a new study shows.
  • The affected area of the brain is involved in cognition, thus linking dental problems to loss of cognitive function and Alzheimer’s disease.
  • For people without severe gum disease, having fewer teeth was linked to brain volume loss.
  • Although the findings suggest a strong link between dental issues and brain volume loss, whether one causes the other is unclear.

A new study finds an association between tooth loss, gum disease, or periodontal disease, and a shrinking of the brain area thought to be involved in memory, and specifically with Alzheimer’s disease. Brain volume is an indicator of atrophy and loss of cognitive function that can occur with age or disease.

Whether poor dental health causes the loss of brain volume or the other way around was beyond the scope of the study. Nonetheless, its findings suggest that good dental health should be prioritized for brain health.

According to the study, a missing tooth was the equivalent of brain shrinkage of nearly an additional year of brain aging, and severe gum disease was equal to 1.3 years of brain aging.

The area of the brain found to be associated with poorer dental health is the left side of the hippocampus. The hippocampus is thought to be linked to learning and memory.

The study involved 172 community-dwelling Japanese individuals. They were an average aages 55 years or older. At study outset, they received thorough dental and periodontal exams, as well as memory tests in which they exhibited no evidence of cognitive decline.

Twice, four years apart, each participant’s brain volume was assessed using magnetic resonance imaging (MRI), and they received additional oral examinations measuring gum disease and tooth loss.

The researchers found that of those without significant gum disease, having fewer teeth corresponded with a greater reduction in hippocampal volume. Perhaps paradoxically, for people with severe gum disease, having more teeth aligned with a greater degree of hippocampal atrophy.

The study is published in Neurology.

“The functional difference between the left and right hippocampus remains controversial, and the details are unknown,” according to the study’s lead author, Dr. Satoshi Yamaguchi from Tohoku University Graduate School of Dentistry, Miyagi in Japan.

Dr. Yamaguchi noted, however, that research points to there being more significant atrophy in the left hippocampus of people with Alzheimer’s disease.

“The left hippocampus plays a crucial role in cognitive abilities, particularly in memory formation and spatial orientation. A decrease in its volume could potentially lead to cognitive impairments, including memory loss and difficulties in spatial navigation,” explained Dr. Bei Wu, vice dean for research at the New York University Rory Meyers College of Nursing, who was not involved in the study.

The study carefully avoids assuming a causal relationship between dental health and hippocampal shrinkage or vice versa.

Dr. Bei Wu offered a hypothesis: “One theory could be that gum disease leads to systemic inflammation.”

“Chronic inflammation is known to have various negative effects on the body, including potential damage to brain cells. This could potentially lead to a decrease in hippocampal volume,” explained Dr. Wu.

He said another idea is that “tooth loss and gum disease could lead to changes in diet and nutrition, which could also impact brain health.”

Dr. Yamaguchi offered two additional possibilities. First, that the same pathogen that drives periodontal disease might invade the brain and damage nerve tissue. Second, “Fewer teeth reduce chewing stimulation, which can lead to brain atrophy,” he said.

Other epidemiological research has linked gum disease and various chronic health conditions, including mental health problems and autoimmune, cardiovascular, and cardiometabolic disease.

That study found that having gingivitis — early-stage gum disease — or periodontal disease was associated with an 18% higher risk of developing cardiovascular disease, a 26% greater risk of developing type 2 diabetes, and a 7% higher chance of developing other cardiometabolic disorders.

According to the CDC, almost half of Americans older than 30 have periodontal disease of some sort. That percentage rises to 70.1% for people older than ages 65 years.

Dr. Yamaguchi said that an important takeaway from the study is that tooth loss and gum disease may have intertwined effects on cognition:

“Because tooth loss and periodontal disease coexist in the mouth and influence each other, they should be considered together. In mild periodontal disease, the effects of inflammation are less pronounced, and thus the association between the number of teeth and brain atrophy may be directly observable.”

Noting the finding that fewer teeth without severe gum disease is associated with reduced hippocampal volume but that more teeth with severe gum disease produces the same result, Dr. Wu said:

“The findings from this study suggest that these factors could be contributing to brain aging in a combined or synergistic manner, rather than independently. Therefore, this study highlights the importance of considering the interaction between tooth loss and gum disease when studying their effects on brain aging.”

“It is important to preserve the health of the teeth and not just retain them. Future studies should validate these findings using data from other cohorts,” Dr. Wu added.