Theoretical and Natural Science · Sep 22, 2026
The Modifying Effect of Multimorbidity on the Association Between Edentulism and Frailty: Evidence from the Longitudinal Ageing Study in India (LASI)
By Wang S
Poor oral health, particularly edentulism, has been independently associated with frailty in older adults across Western and Chinese populations. Multimorbidity is also a well-established risk factor for frailty. Mechanistic studies generally posit a positive synergistic interaction, whereby edentulism and multimorbidity jointly increase frailty risk; however, an attenuating (ceiling) effect cannot be excluded. Whether these two risk factors interact—that is, whether the edentulism–frailty association depends on the level of multimorbidity—remains untested. This study aims to examine the independent and joint associations of edentulism and multimorbidity with frailty among middle-aged and older Indian adults, and to test whether multimorbidity modifies the edentulism–frailty relationship.Cross-sectional analysis of 71,876 adults aged ≥45 years from LASI Wave 1 (2017-2019). Frailty was assessed using a 32-item non-diagnostic frailty index (FI ≥ 0.25), constructed by excluding eight diagnosed chronic diseases to avoid construct overlap with the multimorbidity count (14 physician-diagnosed conditions). Logistic regression models with an edentulism × multimorbidity interaction term were fitted, adjusting for age, sex, residence, education, tobacco use, and alcohol consumption. The results showed that edentulism (OR = 1.21, 95% CI 1.13-1.30) and multimorbidity (OR = 1.58 per condition, 95% CI 1.56-1.61) each independently predicted frailty. The interaction was significant (β = -0.073, p = 0.016) and negative in direction. At 0 chronic conditions, the OR for edentulism was 1.32 (95% CI 1.19-1.45); this declined monotonically with increasing multimorbidity, becoming non-significant at ≥3 conditions (OR = 1.06, 95% CI 0.93-1.21). Sex-stratified analyses showed no significant three-way interaction (p = 0.232).The edentulism–frailty association is strongest when multimorbidity burden is low, and it is progressively diluted as chronic conditions accumulate — a pattern consistent with a ceiling effect. These findings suggest oral health may serve as a target for early frailty prevention, particularly before multimorbidity becomes established.