Associations of number of teeth with risks for all-cause mortality and cause-specific mortality in middle-aged and elderly men in the northern part of Japan: the Iwate-KENCO study.

OBJECTIVES

The objective of this study was to determine the associations of number of teeth with all-cause mortality and cause-specific mortality among middle-aged and elderly Japanese men.

METHODS

A total of 7779 men aged 40-79 years who were free from cardiovascular disease (CVD) were followed up prospectively for 5.6 years. Participants were categorized into four groups (no teeth, 1-9 teeth, 10-19 teeth, and ≥20 teeth) by a self-administered questionnaire. Using Cox's proportional hazard model, multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality from all causes, CVD, cancer, and noncancer, non-CVD according to number of teeth were estimated with adjustments for age, body mass index, systolic blood pressure, total- and HDL-cholesterol, HbA1c, current smoking, current alcohol drinking, and low level of education.

RESULTS

The numbers (proportions) of participants with no teeth, 1-9 teeth, 10-19 teeth, and ≥20 teeth were 1613 (20.7%), 1650 (21.2%), 1721 (22.1%), and 2795 (35.9%), respectively. During follow-up, a total of 455 deaths (including 175 deaths from cancer, 98 deaths from CVD, and 130 deaths from noncancer, non-CVD) were recorded. In total participants, an inverse relationship between number of teeth and all-cause mortality was found (P for trend = 0.049). Among men aged 40-64 years, inverse relationships were also found in risks for mortality from all causes, CVD, and cancer: multivariate-adjusted HRs (95% CI) for all-cause mortality in men with no teeth, 1-9 teeth, and 10-19 teeth relative to men with ≥20 teeth were 2.75 (1.37-5.49), 1.89 (0.99-3.63), and 1.94 (1.09-3.43), respectively. However, there were no associations of number of teeth with all-cause mortality and cause-specific mortality among men aged 65-79 years.

CONCLUSIONS

The number of teeth is an important predictive factor for mortality among middle-aged Japanese men.