Older adults with no teeth left had more trouble with daily tasks in three countries

Losing every natural tooth, which dentists call edentulism, is still common in old age. It is more than a cosmetic problem: without teeth, chewing gets harder, the range of foods a person can manage shrinks, and speaking and smiling in company can become uncomfortable. Earlier studies have found that people with poor oral health tend to lose independence sooner, but most looked at a single country and used a single kind of analysis.

A team at West China Hospital of Stomatology, Sichuan University, asked the same question in three very different countries at once: are older adults with no teeth left more likely to struggle with daily life, and if so, what might connect the two?

What they did

The researchers used three large national ageing studies whose data have been put into a common format, so the same questions can be compared across countries: the English Longitudinal Study of Ageing, the US Health and Retirement Study and the Longitudinal Ageing Study in India. Together they included 63,074 people aged 60 or older. About one in five in England (20.0%), one in four in the US (25.1%) and about one in nine in India (11.2%) had lost all their natural teeth.

The outcomes were two standard measures of independence:

• Basic daily activities: dressing, bathing, eating, getting in or out of bed and using the toilet.
• Household activities: cooking, shopping, using the phone, managing medicines and handling money.

A person counted as having a disability if they had difficulty with at least one item on a list.

Because people without teeth differ in many ways (they were older, for example), the team used a statistical weighting method that makes the groups comparable on age, sex, education, marital status, smoking, drinking, falls and a list of chronic diseases. In England and the US, they also followed people who had no disability at the start, to see who developed one later. Finally, they tested whether three things might carry the link: grip strength (a simple marker of overall muscle strength), body mass index and depressive symptoms.

What they found

• More disability among people without teeth. In England, 42.5% of people without teeth had trouble with basic daily activities, compared with 25.7% of those with teeth. The gaps were similar in the US (42.5% vs 27.5%) and India (31.2% vs 19.6%).
• Still there after accounting for other differences. Across the three countries combined, having no teeth was linked to roughly 30% higher odds of difficulty with basic activities (odds ratio 1.30) and 27% higher odds for household activities (1.27). The link was weaker in India for household tasks.
• Over time, too. Among English and US participants who started without any disability, those without teeth were more likely to develop problems later: about 19% more often for basic activities (hazard ratio 1.19) and 30% more often for household activities (1.30). For basic activities, the English result on its own was not statistically significant.
• Grip strength explained a large part. In the English and US data, weaker grip accounted for roughly half of the link (about 45–53%, depending on the measure); in India only 5–14%. Depressive symptoms explained little, and body mass index almost nothing.
• A hint about dentures. In India, the only study with usable denture data, people without teeth who had dentures had about a third lower odds of disability than those without dentures (odds ratios 0.66 and 0.65).

What to keep in mind

• Hidden differences. The authors call leftover confounding, other factors that affect both teeth and independence, the main threat to their conclusions. Wealth, lifelong nutrition, access to dental and medical care, frailty and memory and thinking were only partly measured.
• Which came first is unclear. Disability, poor nutrition and difficulty with self-care could themselves speed up tooth loss. The follow-up analyses help with the order of events, but they covered only two countries and are still observational.
• The grip-strength figures are approximate. Grip and disability were mostly measured at the same time. When the team measured tooth loss, grip and disability years apart, the share explained by grip shrank. The authors say the numbers show the relative importance of muscle strength, not an exact split.
• The denture finding is exploratory. It comes from one country, one point in time, and people who get dentures may simply have more money and better access to care. The authors call it "hypothesis-generating".
• Not identical measures. The depression questionnaires and household-task questions differed somewhat between countries, which may explain some of the differences between them.

Why it matters

Losing all one's teeth tracked with losing independence in three countries with very different health systems, and the pattern held up across several ways of analysing the data. The link with grip strength fits the idea that poor chewing could lead to poorer nutrition and weaker muscles, though this study cannot prove that chain (loss of muscle with age is called sarcopenia). The authors suggest that complete tooth loss may be a useful signal that an older person needs a closer look at their strength, mood and daily functioning, and that the denture question deserves studies that follow people forward in time or test it directly.