Sleep duration and remaining teeth among older people

Highlights

• Our cross-sectional population-based study offers a link between fewer teeth and sleep disturbance.

• Older adults with less than 10 teeth slept shorter or longer than 7 h.

• Sleep disturbance was severer among edentulous individuals compared to the rest of the individuals.

• Further experimental investigations on oral health and sleep disturbance will validate the suggested cross-sectional link.

Abstract

Background

No studies have examined the associations between the numbers of teeth and sleep disturbance. Therefore, we examined the associations between the number of teeth and sleep duration in older people, considering the evidence linking fewer teeth and sleep apnoea through changes in jaw position.

Methods

For this study we used information from a sample of 23,444 cohort participants, randomly selected from the Japan Gerontological Evaluation Study 2010 (N = 169,215). The outcome variable was self-reported sleep duration (h/day), and the explanatory variable was self-reported number of teeth (0, 1–9, 10–19, ≥20). We treated age, sex, body mass index, educational attainment, annual equalized household income, depressive symptoms, physical activity, activities of daily living, presence of diabetes, and smoking status as covariates. Multinomial logistic regression was used among the 20,548 eligible participants with all necessary information.

Results

The mean age was 73.7 (standard deviation = 6.13) years. Most participants (28.1%) reported sleep duration of 7 h, while a small proportion of the participants reported short (≤4 h, 2.7%) or long (≥10 h, 4.7%) sleep duration. The proportion of edentulous participants was 14.7%. Taking the 7-h sleep duration as the reference category, edentulous participants (relative risk ratio (RRR) = 1.43, 95% confidence interval (CI) = 1.07–1.90) or one to nine teeth (RRR = 1.29, 95% CI = 1.02–1.63) had a significantly higher relative risk ratio for short sleep, independent of covariates. Furthermore, they had a higher relative risk ratio for long sleep duration (RRR = 1.75, 95% CI = 1.40–2.19; RRR = 1.48, 95% CI = 1.21–1.81, respectively).

Conclusions

Compared to people with 20 or more teeth, older adults with fewer than 10 teeth have higher risks for short and long sleep durations.

Introduction

Sleep disturbance is an important public health issue in an ageing society, given the high prevalence in sleep problems of the adult population aged 60 and over [1], which is expected to reach two billion in 2050 worldwide [2]. Long sleep duration as well as short sleep duration has been linked to increased all-cause mortality among older people [3], [4]. Additionally, laboratory and epidemiologically based studies have shown that self-reported short and long sleep durations were associated with increased risks of cardiovascular disease [5], diabetes mellitus [6], [7], obesity [6], poor cognitive performance [8], [9], and poor self-rated health [10].

Sleep apnoea is a main cause for inadequate sleep duration. Obstructive sleep apnoea (OSA) is characterized by shorter slow wave sleep and longer apnoea [11]. It is closely linked with retraction of the tongue root [12] or resting tongue position [13], [14], [15]. Loss of dental occlusion is known to cause protrusion of jaw position, which leads to retraction of the tongue root, while being edentulous (ie, having no teeth) contributes to the resting tongue position. Therefore, we hypothesized that the number of teeth, especially fewer teeth, may be associated with sleep disturbance. Older adults with fewer teeth are likely to have short sleep duration as well as long sleep duration compared with those who have more teeth.

To the best of our knowledge, no studies have examined the associations between the number of teeth and sleep duration. Thus, the aim of our study was to offer an empirical link between the numbers of teeth and sleep duration.