The overall goal of our meta-analysis is to determine whether there is an association between tooth number and frailty by combining the results of previous studies. We found that older adults with teeth less than 20 were at greater risk of frailty than those with teeth more than 20. To our knowledge, this is the first meta-analysis providing comprehensive insights into the relationship between the number of teeth and frailty. This meta-analysis clearly shows that maintaining the number of teeth is critical for frailty in older adults.
Our meta-analysis showed that tooth loss increased the probability of frailty by 2% for each additional tooth (95% CI: 0.97–0.99, P < 0.01), which seemed to have little effect on frailty. However, compared to older adults with teeth more than 20, those with teeth fewer than 20 had a 91% higher risk of frailty (95% CI: 1.48–2.47, P < 0.01). A large study with a sample size of over 3,000 people showed that those with teeth more than 20 had a 2.47-fold higher risk of frailty than those with teeth fewer than 20 16. Therefore, we believe that tooth loss increases the risk of frailty. However, it should be noted that this relationship refers to a loss of natural teeth rather than dentures increasing the risk of frailty. At present, dentures cannot be considered to be associated with frailty13. This suggests that we may not delay the occurrence and development of frailty through dentures, so we should pay more attention to oral health and maintain the number of natural teeth.
. A previous meta-analysis showed that female sex, single or widowed status, depression, diabetes, arthritis, urinary incontinence, chronic obstructive pulmonary disease, stroke, malnutrition, and history of falls were risk factors for frailty in older adults27. However, our meta-analysis showed that tooth loss increases the risk of frailty in subgroup analyses for country, not in subgroup analyses for age, type of study design, setting, and frailty assessment tools. In country subgroup, it is interesting to note that PFP and Frailty Index are the two most commonly used assessment tools in large sample studies. Actually, the Frailty Index and PFP were primarily used in the literature reviewed in this meta-analysis. The Frailty Index contains a total of 30 items, while PFP contains only 5 items. Using the Frailty Index to assess frailty is more comprehensive and has less heterogeneity in the population than PFP. Thus, the Frailty Index can screen out the possibility of frailty more than PFP.
In addition, even using the same assessment tool, results may vary widely among different populations. For instance, when using Frailty Index, one conducted in Chinese showed that the risk of frailty was 2.47-fold (95% CI: 2.71–4.45) higher in studies with more than 20 missing teeth16, while in America had a 28% (95% CI: 1.15–1.42) increased risk1. Future results may be different if more studies use the Frailty Index. In fact, in addition to the frailty index and PFP, there are assessment tools such as the Clinical Frailty Scale28, Tilburg Frailty Indicator29, and FRAIL Scale30. However, there is heterogeneity in the grading and power of these tools. When choosing an assessment tool, it is important to not only consider whether it can accurately identify frailty patients but also consider resources in specific clinical settings31. Therefore, it is suggested that more prospective studies be conducted to further investigate the impact of different frailty assessment tools on frailty screening.
Understanding the mechanisms involved in tooth loss and frailty is important for reducing the prevalence of frailty. However, the mechanisms are not clear, and the two may be linked through nutritional, inflammatory, psychological, and neurological pathways32. Older adults with tooth loss face the risk of inadequate nutritional intake, while inadequate intake of elements such as protein and vitamins increases the risk of frailty in older adults 33, 34. Another potential mechanism is inflammation. An important cause of tooth loss in older adults is periodontitis, which reflects not only local oral symptoms but also increases in peripheral inflammatory biomarkers such as lymphocytes, IL-6, CRP, and TNF-α, while inflammation can lead to loss of muscle mass and reduced physical activity 35. In addition, dental injury may reflect damage to the occlusal and proprioceptive nerves of the periodontal ligament, which regulate body balance32. Finally, it may also occur through a psychological pathway. Older adults with tooth loss may have disturbed body imagery, and this imbalance may lead to negative conditions such as lack of socialization and depression. Studies have shown that among older adults, living alone is associated with a 28% higher risk of frailty than not living alone36, being lonely is associated with a 41% higher risk of frailty than not being lonely 37, and being depressed is associated with a 1.06-fold higher risk of frailty than not being depressed38.
Our meta-analysis has several advantages. To our knowledge, this is the first meta-analysis to summarize the evidence on the relationship between the number of teeth and frailty. Second, we included all available observational studies with large sample sizes and employed multiple methodological analyses, including subgroup analyses, sensitivity analyses, and publication bias tests, suggesting that the observed associations may be robust.
There are certain limitations to our meta-analysis. First, the overall number of studies and follow-up studies was small and did not better explore the long-term effects of tooth loss on frailty. Second, most of the data originate from Asian countries, which are unable to reflect the overall situation of the world due to the uneven distribution of the data among countries. Third, the frailty included in the literature mainly refers to physical frailty. Therefore, we lacked the effects of tooth loss on other frailty, such as cognitive frailty and social frailty. Fourth, there may be publication bias, as the quality of the included studies varied.
The findings of our meta-analysis have significant implications for medical practice. Currently, the association between age and tooth loss remains unclear39, 40, while frailty is related to age. It is difficult to stop the aging process, so it is important to intervene in tooth loss. The problem is that more than half of the patients had dental and periodontal problems, while two-thirds of the edentulous patients did not visit the dentist regularly or at all41. Currently, management of frailty mainly consists of nutrition, exercise, and medication use42. Our study reflects that preserving the quantity of natural teeth are crucial for preventing the occurrence and development of frailty.