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RESEARCH REPORT |
1 Dept. of Health Policy & Health Services Research and
2 Dept. of Periodontology and Oral Biology, Boston University Goldman School of Dental Medicine, 715 Albany St., 560, 3rd floor, Boston, MA 02118, USA;
3 Dept. of Epidemiology, Harvard School of Public Health;
4 New England Research Institutes;
5 University of Puerto Rico, Division of Dental Public Health, School of Dentistry, Medical Science Campus; and
6 VA Normative Aging Study, VA Boston Healthcare System
* corresponding author, tdietric{at}bu.edu
| ABSTRACT |
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KEY WORDS: periodontitis smoking tobacco tooth loss
| INTRODUCTION |
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The use of other types of tobacco, such as cigar, pipe, and smokeless tobacco, is also likely to be related to tooth loss risk, but few studies have explored this hypothesis. A cross-sectional analysis of 705 participants in the Baltimore Longitudinal Study of Aging found that the number of missing teeth was higher among smokers of pipes and cigars (Copeland et al., 2004). Both pipe- and cigar-smoking were independently associated with increased tooth loss risk in a longitudinal study of 690 men (Krall et al., 1999). In a representative survey of the US population (NHANES III), history of smokeless tobacco use was associated with periodontal disease prevalence (Fisher et al., 2005). However, whether or not the use of smokeless tobacco increases the risk of tooth loss has not been investigated.
The purpose of the present study was to evaluate the associations between the various forms of tobacco use (cigarette smoking, pipe or cigar smoking, chewing tobacco) and smoking cessation and the incidence of tooth loss in a large, prospective study of US health professionals.
| MATERIALS & METHODS |
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For the present analysis, we excluded men if, at baseline, they had: missing data for cigarette smoking status, a cancer diagnosis by 1986, self-reported daily caloric intake outside the plausible range of 800 to 4200, or > 70 of the 131 dietary questions left blank. We also excluded 742 edentulous men (29% never, 57% former, and 15% current cigarette smokers). The final analytic sample included 43,112 men who contributed 569,366 person-years.
Exposure Assessment
The baseline HPFS questionnaire asked detailed questions on the history of cigarette smoking. Men who had smoked fewer than 20 packs of cigarettes in their lifetime were defined as never-smokers. Ever-smokers of cigarettes reported the average number of cigarettes per day (04, 514, 1524, 2534, 3544, 45+ cig/d) and, if former smokers, time since cessation (< 1 yr, 12 yrs, 35 yrs, 69 yrs, 10+ yrs). Information on cigarette and cigar or pipe smoking (current, yes/no) was updated biennially. Ever-use of chewing tobacco was ascertained in the 1996 questionnaire ("Have you ever chewed tobacco at least once a week for a year?").
Outcome Assessment
Participants reported baseline number of teeth in 1986 and incident tooth loss in two-year intervals thereafter. Missing values on incident tooth loss were assumed to represent no tooth loss during that follow-up period, because only
10% of participants experienced tooth loss biennially. Self-reported number of teeth and tooth loss have been found to be highly accurate in various populations (Douglass et al., 1991; Gilbert et al., 2002; Pitiphat et al., 2002). Thus, in this population of dentists and health professionals, self-reported number of teeth and tooth loss are likely to have high validity.
Assessment of Potential Confounders
Diet was assessed at baseline and every 4 yrs thereafter with an expanded semi-quantitative food frequency questionnaire (Willett et al., 1985). Every 2 yrs, questionnaires also assessed use of multivitamins and specific vitamin supplements. Validity of the dietary data has been documented by comparisons with multiple weighted dietary records (Rimm et al., 1992). Physical activity was assessed biennially and calculated as the sum of the activity-specific metabolic equivalent (MET) hrs/wk as a measure of total leisure-time physical activity.
Data Analysis
Person-time for each participant was calculated from the date of return of the 1986 questionnaire to the date of first incident tooth loss, death, or January 31, 2002, whichever occurred first.
We used Cox proportional-hazards models to obtain hazard ratios and 95% confidence intervals for the association between tobacco use and risk of tooth loss. Former smokers were categorized according to time since cessation (< 1, 12, 35, 69, and 10+ yrs ago), and current smokers were categorized according to intensity (< 5, 514, 1524, 2534, 3544, 45+ cigarettes/day).
All models contained cigarette, cigar/pipe, and chewing tobacco variables, mutually adjusted for type of tobacco use. The basic model included age (mos) and race (Caucasian vs. other). A multivariable model further adjusted for other variables that were significantly associated with tooth loss (p < 0.05) in bivariate analyses, or that changed the effect estimates of the tobacco use/tooth loss association by > 5%. Cigarette smoking, pipe/cigar smoking, body mass index (BMI), physical activity, diabetes, use of multivitamins/vitamin supplements, and intakes of nutrients/food groups were modeled as time-dependent variables.
Sensitivity analyses restricted the cohort to dentists, because reasons for tooth loss and accuracy of self-reports may differ from those of non-dentists. Finally, because smoking increases the risk of various cancers and cancer treatment (i.e., radiotherapy and chemotherapy) that may be associated with increased tooth loss, a separate analysis censored person-time at the follow-up preceding a first report of a cancer diagnosis.
All statistical tests were two-sided and calculated by SAS 9.1.2 (SAS Institute Inc., Cary, NC, USA).
| RESULTS |
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Current pipe or cigar smoking was associated with a 20% (multivariate HR, 1.20; 95% CI, 1.11, 1.30) increased risk of tooth loss compared with never- or former smokers of pipes or cigars. Results were similar when the analysis was restricted to dentists. Ever-use of chewing tobacco was associated with incident tooth loss in the age- and race-adjusted analysis (HR, 1.27; 95% CI, 1.16, 1.39), as well as in the full multivariate model (HR, 1.14; 95% CI, 1.04, 1.24), although the association was attenuated when additional covariates were included. When analysis was restricted to dentists, however, no statistically significant association between chewing tobacco and tooth loss was observed (HR, 1.06; 95% CI, 0.90, 1.26).
Censoring of person-time prior to a first diagnosis of cancer did not change the results (data not shown).
| DISCUSSION |
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Important strengths of this study are its prospective design, large sample size, long follow-up, and detailed, biennially updated data on smoking, allowing for fine exposure categories and precise estimates. When one considers that tooth loss is the outcome of a complex process that may involve numerous factors that are also related to tobacco use (e.g., diet, health behaviors), another strength of this study is our ability to control adequately for such confounders. Furthermore, the cohorts relative homogeneity minimizes potential confounding by factors such as socio-economic status and access to care.
The path by which cigarette smoking affects tooth loss is presumed to involve periodontitis. In addition to periodontitis, dental caries may also contribute to the increased risk of tooth loss among smokers (Ylostalo et al., 2004). Associations have been reported between cigarette smoking and root caries (Hahn et al., 1999; Fure, 2004; Phelan et al., 2004), coronal caries (Drake et al., 1997; Axelsson et al., 1998), endodontic treatment (Krall et al., 2006a), and periapical periodontitis (Kirkevang and Wenzel, 2003), although not consistently (Bergström et al., 2004).
We found that risk of tooth loss declines as early as 1 yr after smoking cessation. However, it may take more than 10 yrs of abstinence for the risk to decline to that of never-smokers. This is in agreement with results from the VA Dental Longitudinal Study, where, after 12 yrs of cessation, the risk of tooth loss approached that of never-smokers (Krall et al., 1997, 2006b).
These results suggest that, following smoking cessation, the effect of smoking on tooth loss declines less rapidly than the effect of smoking on periodontitis (Bolin et al., 1993; Bergström et al., 2000; Tomar and Asma, 2000). Using NHANES III data, we estimated the half-life of the effect of smoking on periodontal disease at 1.5 yrs (Dietrich and Hoffmann, 2004), suggesting that the risk for periodontal disease for former smokers should approach that of never-smokers approximately 6 yrs after quitting. This apparent difference in the half-life of the effects of smoking on periodontal disease vs. tooth loss may be explained by factors other than periodontitis, such as caries, that also mediate the effect of smoking on tooth loss risk.
Our finding that cigar or pipe smoking is associated with risk of tooth loss confirms results of earlier work. In a cross-sectional study, men who smoked pipes or cigars had a higher prevalence of moderate or severe periodontitis and fewer teeth remaining than did non-smokers (Albandar et al., 2000). In an earlier longitudinal study, we found that cigar smoking is associated with significantly higher rates of tooth loss (Krall et al., 1999). However, it is uncertain by exactly how much the risk increases, since we had only a dichotomous measure of current cigar or pipe smoking, i.e., the comparison group included both never- and former smokers.
We found a significant positive association between ever-use of chewing tobacco and risk of tooth loss only among the non-dentist health professionals. Previous studies of smokeless tobacco and tooth loss are lacking, and our results should be interpreted with caution. Multivariable adjustment resulted in a marked attenuation of the hazard ratio, and no association was evident when the analysis was restricted to dentists. Although residual or unknown confounding may explain the small association found, it is likely that our measure of chewing tobacco use was insufficient to estimate accurately an association with tooth loss. We did not have specific information on dose, duration, or timing (i.e., ages) of chewing tobacco use, and it may be that a great many ever-users were men who had used chewing tobacco in the distant past.
Our results provide evidence for a strong time- and dose-dependent association between tobacco smoking and risk of tooth loss among men. However, these results may not be directly generalizable to women. In a cross-sectional study of 8409 young Finnish adults, a somewhat stronger association between smoking and tooth loss was reported among women (Ylostalo et al., 2004). Last, since the majority of HPFS participants were Caucasian, generalizability of our findings to other racial/ethnic groups is uncertain.
In conclusion, there is a strong association between cigarette, pipe, or cigar smoking and subsequent tooth loss in men. Current heavy cigarette smokers have a three-fold greater risk of incident tooth loss, compared with never-smokers. The risk declines soon after cessation of cigarette smoking, but remains elevated for more than 10 yrs compared with risk in never-smokers.
| ACKNOWLEDGMENTS |
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Received April 1, 2006; Last revision September 19, 2006; Accepted December 5, 2006
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