Verification of the criteria for reduced occlusal force to diagnose oral hypofunction in older Japanese people: A prospective cohort study on incident functional disability

In 2016, the Japanese Society of Gerodontology (JSG) proposed the concept of “oral hypofunction (OHF),” and recommended two initial criteria for reduced occlusal force (ROF): <200 N of maximum occlusal force (MOF) and < 20 remaining teeth. However, the JSG stated that these criteria need to be reviewed by accumulating further evidence. To examine the validity and equivalence of the two criteria for ROF in the diagnostic criteria for OHF by using the incidence of functional disability as the outcome. This study enrolled 815 community-dwelling Japanese individuals ≥ 70 years. They underwent examinations for physical, mental and social functions; MOF; and number of teeth at baseline. The incidence of functional disability (a condition that requires at least partial assistance with daily activities) based on the first certification of long-term care insurance was followed up. The Cox proportional hazard model revealed that MOF < 200 N (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.04-1.72) and < 20 teeth (HR, 1.40; 95% CI, 1.07-1.84) were significantly associated with increased risk of functional disability. Receiver operating characteristic curve analyses revealed that the optimal cut-off values of MOF and number of teeth that best predicted incident functional disability were 264.6 N and 19 teeth, respectively. Twelve teeth were the optimal threshold that best predicted < 200 N of MOF. The two criteria for ROF in the diagnostic criteria for OHF had some degree of validity. However, further studies are needed to develop appropriate and reliable criteria for a decision of ROF.