Dental hygiene key to predicting mortality, Japanese researchers find

by Jessica Speed at japatimes.com.jp

Poor oral health among older adults is closely linked to higher mortality rates and a higher risk of requiring long-term care, according to two separate large-scale studies by researchers at Osaka Metropolitan University and the Institute of Science Tokyo.

A research team led by Osaka Metropolitan University analyzed dental checkup data from 190,282 residents of Osaka Prefecture age 75 or older who underwent examinations from fiscal 2018 to 2020.

The study examined the relationship between dental condition and all-cause mortality (deaths linked to any cause), and found that death rates were lower among people with a higher number of healthy or treated teeth, while those with untreated cavities faced increased risks.

Older adults with no remaining teeth had a mortality risk about 1.7 times higher than those with 21 or more teeth, according to the study. The researchers suggested that this may be because untreated tooth decay can impair chewing ability and contribute to chronic inflammation, which can affect nutrition and overall physical health.

The analysis also showed that counting healthy and treated teeth was the most accurate way to predict all-cause mortality, outperforming measures that included untreated teeth, or counting only healthy teeth.

The findings were published online in November in the international journal BMC Oral Health, and are part of a broader epidemiological effort using large-scale real-world data from dental checkups and long-term care records in Osaka Prefecture. Researchers said the results could help refine how oral health is assessed in older adults and used as an indicator of future health risks.

The study builds on Japan’s long-running “8020 Campaign,” which encourages people to retain at least 20 of their own teeth by age 80. Achievement rates for the campaign reached 61.5% as of July, up from around 10% when it began in 1989.

“We hope that this is an opportunity to use the results of this study to help promote early treatment and regular dental care,” said Naoko Otsuki, the lecturer who led the study.

Separately, researchers at the Institute of Science Tokyo, led by professor Jun Aida, have recently examined the impact of oral frailty — a decline in oral function — on healthy life expectancy. Using nationwide data from 11,080 older adults tracked over six years, the team analyzed links between oral health, dental visits and transitions to disability or death.

In the study, oral frailty was defined as having three or more symptoms, including few remaining teeth, difficulty chewing or swallowing, dry mouth or difficulty speaking. Such declines are known to reduce food intake, physical strength and social interaction, all of which can accelerate health deterioration among older adults.

People with oral frailty had a 1.23 times higher risk of requiring long-term care and a 1.34 times higher risk of death compared with those without the condition. Healthy life expectancy at age 65 was about 1.4 to 1.5 years shorter for people with oral frailty, while those who visited the dentist regularly had a healthy life expectancy roughly one year longer on average, the study found.

The Tokyo researchers stated that going forward it will be important to develop policies to promote the prevention of oral frailty, encourage regular dental visits, and strengthen community-based oral health activities.

They also emphasized the need to further strengthen cooperation between dental care and medical care and to build a system that supports healthy old age in Japan’s superaging society.