Relationship between survival rates and numbers of natural teeth in an elderly Japanese population.
OBJECTIVES: The objective of this study was to assess whether elderly people with 20 or more natural teeth were more likely to live longer than a cohort with less than 20 teeth. MATERIALS AND METHODS: Groups of elderly people over 80 years of age (24 males and 35 females) with 20 or more teeth (>or=20 group) were compared with elderly people (24 males and 35 females) with less than 20 teeth (<20 group). Follow-up studies were conducted at regular intervals for 10 years from July 1992 to July 2002. The cumulative survival rate of the >or=20 group (average +/- SE tooth number of teeth - males, 23.9 +/- 0.6; females, 23.8 +/- 0.4) was compared with the <20 group (average number of teeth - males, 3.8 +/- 1.1; females, 2.6 +/- 0.8). The multivariate Cox proportional hazard models with the number of teeth in a group (>or=20 group or <20 group). Smoking status and alcohol intake as covariates were used to adjust the cumulative survival rate. RESULTS: The male participants in the >or=20 group had a significantly higher cumulative survival rates (p < 0.05) than the <20 group at 18 and 21 months from baseline. There were no significant differences in survival rates between the female groups. Adjusted cumulative survival rate was significantly different at 72, 75 and 78 months between the >or=20 group and <20 group for males but not for females. CONCLUSION: Having 20 or more natural teeth was associated with increased survival rate in elderly males, but not among the elderly females.