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.
OBJECTIVE
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.
Department of Hygiene and Preventive Medicine, School of Medicine, Iwate Medical University, Yahaba, Japan.
Ayumi
A
Ando
Kozo
K
Tanno
Masaki
M
Ohsawa
Toshiyuki
T
Onoda
Kiyomi
K
Sakata
Fumitaka
F
Tanaka
Shinji
S
Makita
Motoyuki
M
Nakamura
Shinichi
S
Omama
Kuniaki
K
Ogasawara
Yasuhiro
Y
Ishibashi
Toru
T
Kuribayashi
Tomiko
T
Koyama
Kazuyoshi
K
Itai
Akira
A
Ogawa
Akira
A
Okayama
D000368:Aged; D002423:Cause of Death; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D016388:Tooth Loss / Q000401:mortality*
epidemiology; oral health; periodontal diseases; risk assessment