Miyo Nakade

Association Between Self-reported Dental Health Status and Onset of Dementia: A 4-year Prospective Cohort Study of Older Japanese Adults from the Aichi Gerontological Evaluation Study (ages) Project

Objectives Studies have shown that people with cognitive impairment have poor dental health. However, the direction of causality remains unknown. This prospective cohort study aimed to determine the association between four self-reported dental health variables and dementia onset in older Japanese people. Methods Analysis was conducted on 4425 residents 65 years or older. Four self-reported dental health variables included the number of teeth and/or use of dentures, ability to chew, presence/absence of a regular dentist, and taking care of dental health. Data were collected using self-administered questionnaires given in 2003. Records of dementia onset during 2003 to 2007 were obtained from municipalities in charge of the public long-term care insurance system. Age, income, body mass index, present illness, alcohol consumption, exercise, and forgetfulness were used as covariates. Results Dementia onset was recorded in 220 participants. Univariate Cox proportional hazards models showed significant associations between the dental health variables and dementia onset. In models fully adjusted for all covariates, hazard ratios (95% confidence intervals) of dementia onset of respondents were as follows: 1.85 (1.04–3.31) for those with few teeth and without dentures; 1.25 (0.81–1.93) for those who could not chew very well; 1.44 (1.04–2.01) for those who did not have a regular dentist; and 1.76 (0.96–3.20) for those who did not take care of their dental health. Conclusions Few teeth without dentures and absence of a regular dentist, not poor mastication and poor attitudes toward dental health, were associated with higher risk of dementia onset in the older Japanese cohort even after adjustment for available covariates. Abbreviations AGES = Aichi Gerontological Evaluation Study; BMI = body mass index; HR = hazard ratio; CI = confidence interval

Oral Health and Cancer, Cardiovascular, and Respiratory Mortality of Japanese

Cardiovascular diseases, cancer, and respiratory disease are major causes of death in developed countries. No study has simultaneously compared the contribution of oral health with these major causes of death. This study examined the association between oral health and cardiovascular diseases, cancer, and respiratory mortality among older Japanese. Self-administered questionnaires were mailed to participants in the Aichi Gerontological Evaluation Study (AGES) Project in 2003. Mortality data were analyzed for 4425 respondents. Three categories of oral health were used: 20 or more teeth, 19 or fewer teeth and eat everything, 19 or fewer teeth and eating difficulty. Sex, age, body mass index (BMI), self-rated health, present illness, exercise, smoking, alcohol, education, and income were used as covariates. During 4.28 years’ follow-up, 410 people died, 159 from cancer, 108 of cardiovascular diseases, and 58 of respiratory disease. Multivariate adjusted Cox proportional hazard models showed that, compared with the respondents with 20 or more teeth, respondents with 19 or fewer teeth and with eating difficulty had a 1.83 and 1.85 times higher hazard ratio for cardiovascular disease mortality and respiratory disease mortality, respectively. There was no significant association with cancer mortality. Oral health predicted cardiovascular and respiratory disease mortality but not cancer mortality in older Japanese.

Association between dental status and incident disability in an older Japanese population.

To determine the association between dental health status and onset of functional disability in older Japanese people.

Can breakfast tryptophan and vitamin B6 intake and morning exposure to sunlight promote morning-typology in young children aged 2 to 6 years?

This study tried to examine, from epidemiological and physiologic anthropological (Japanese culture on breakfast) points of view, the integrated effects of the amount of tryptophan and vitamin B6 intake and the following exposure to sunlight on the circadian typology and sleep habits in young Japanese children aged 2 to 6 years, using the newly-evaluated calculating system of tryptophan (Tryptophan Index 2009) and vitamin B6 intake (VitaminB6 Index 2009) at breakfast. The positive and significant correlation was shown between the Morningness-Eveningness (M-E) score and the Tryptophan Index and also the Vitamin B6 Index. This positive correlation between M-E score and amount of tryptophan intake was shown only by children who were exposed to sunlight for longer than 10min after breakfast. These results might support the following hypothesis: higher tryptophan and vitamin B6 intake at breakfast could promote the synthesis of serotonin via light stimulation in the morning in children.

A tryptophan-rich breakfast and exposure to light with low color temperature at night improve sleep and salivary melatonin level in Japanese students

Background Epidemiological studies in Japan have documented an association between morning type and a tryptophan-rich breakfast followed by exposure to sunlight in children. The association may be mediated by enhanced melatonin synthesis, which facilitates sleep at night. However, melatonin is inhibited by artificial light levels with high color-temperature common in Japanese homes at night. In this study, we investigated whether a combination of tryptophan-rich breakfast and light with low color-temperature at night could enhance melatonin secretion and encourage earlier sleep times. Methods The intervention included having breakfast with protein- and vitamin B6 - rich foods and exposure to sunlight after breakfast plus exposure to incandescent light (low temperature light) at night (October-November, 2010). The participants were 94 members of a university soccer club, who were divided into 3 groups for the intervention (G1: no intervention; G2: asked to have protein-rich foods such as fermented soybeans and vitamin B6-rich foods such as bananas at breakfast and sunlight exposure after breakfast; G3: the same contents as G2 and incandescent light exposure at night). Salivary melatonin was measured around 11:00 p.m. on the day before the beginning, a mid-point and on the day before the last day a mid-point and on the last day of the 1 month intervention. Results In G3, there was a significantly positive correlation between total hours the participants spent under incandescent light at night and the frequency of feeling sleepy during the last week (p = 0.034). The salivary melatonin concentration of G3 was significantly higher than that of G1 and G2 in combined salivary samplings at the mid-point and on the day before the last day of the 1 month intervention (p = 0.018), whereas no such significant differences were shown on the day just before the start of the intervention (p = 0.63). Conclusion The combined intervention on breakfast, morning sunlight and evening-lighting seems to be effective for students including athletes to keep higher melatonin secretion at night which seems to induce easy onset of the night sleep and higher quality of sleep.

Dental status and incident falls among older Japanese: a prospective cohort study

Objective To examine if self-reported number of teeth, denture use and chewing ability are associated with incident falls. Design Longitudinal cohort study (the Aichi Gerontological Evaluation Study). Setting 5 Japanese municipalities. Participants 1763 community-dwelling individuals aged 65 years and older without experience of falls within the previous year at baseline. Main outcome measures Self-reported history of multiple falls during the past year at the follow-up survey about 3 years later. Baseline data on the number of teeth present and/or denture use and chewing ability were collected using self-administered questionnaires. Logistic regression analyses controlled for sex, age, functional disability during follow-up period, depression, self-rated health and educational attainment. Results 86 (4.9%) subjects reported falls at the follow-up survey. Logistic regression models fully adjusted for all covariates showed that subjects having 19 or fewer teeth but not using dentures had a significantly increased risk for incident falls (OR 2.50, 95% CI 1.21 to 5.17, p=0.013) compared with those having 20 or more teeth. Among subjects with 19 or fewer teeth, their risk of falls was not significantly elevated so long as they wore dentures (OR 1.36, 95% CI 0.76 to 2.45, p=0.299). No significant association was observed between chewing ability and incident falls in the fully adjusted model. Conclusions Having 19 or fewer teeth but not using dentures was associated with higher risk for the incident falls in older Japanese even after adjustment for multiple covariates. Dental care to prevent tooth loss and denture treatment for older people might prevent falls, although the authors cannot exclude the possibility that the association is due to residual confounding.

Social determinants of denture/bridge use: Japan gerontological evaluation study project cross-sectional study in older Japanese

BackgroundStudies suggest that using a denture/bridge may prevent disability in older people. However, not all older people with few remaining teeth use a denture/bridge. This cross-sectional study aimed to examine the social determinants which promote denture/bridge use among older Japanese.MethodsA total of 54,388 (25,630 males and 28,758 females) community-dwelling individuals aged 65 or over, living independently, able to perform daily activities, and with 19 or fewer teeth. The dependent variable was denture/bridge use. Socio-demographics, number of teeth, present illness, social participation, social support, and social networks were used as individual-level independent variables. Data for social capital were aggregated and used as local district (n = 561 for males, n = 562 for females) -level independent variables. Number of dentists working in hospitals/clinics per population and population density were used as municipality (n = 28) -level independent variables. Three-level multilevel Poisson regression analysis was performed for each sex.ResultsHigh equivalent income, low number of teeth, present illness, and living in a municipality with high population density were significantly associated with denture/bridge use in both sexes in the fully adjusted models (p < 0.05). Denture/bridge use was significantly associated with high educational attainment in males and participating in social groups in females in the fully adjusted model (p < 0.05). No significant associations were observed between denture/bridge use and social capital.ConclusionsDenture/bridge use was significantly associated with high economic status and present illness in both sexes, high educational attainment in males, and participation in social groups in females among community-dwelling older Japanese after adjusting for possible confounders.

Mental Health of Children from a Chronobiological and Epidemiological Point of View

In 24-hour society seen especially in developed countries including Japan, fluctuations in the environmental conditions that act as zeitgebers for the circadian clock, such as light, meals and even social activities (e.g. “flextime”) tend to become irregular and with decreasing amplitudes. Using mobile phones, playing video games, and frequenting 24-hour stores may accelerate this irregularity of environmental diurnal rhythms. These circumstances lead to weaker zeitgebers for entraining circadian clocks in children and promote a shift to the evening-typed diurnal rhythms in daily life. This evening-typed life style may potentially cause a decline in mental health in children via these three physiological mechanisms:

Poor Oral Health and Diet in Relation to Weight Loss, Stable Underweight, and Obesity in Community-Dwelling Older Adults: A Cross-Sectional Study From the JAGES 2010 Project

Background Involuntary weight loss and underweight increase the risks of mortality and disability in older people. However, the association and interaction of poor oral health and dietary intake with body mass index (BMI) have not been elucidated. Methods Data were analyzed for 96 794 respondents aged >65 years who were randomly selected from 31 Japanese municipalities in the Japan Gerontological Evaluation Study. Weight loss was defined as ≥2–3 kg of loss over the preceding 6 months. BMI was evaluated in respondents without weight loss. Multiple logistic regression analysis was performed with weight loss, underweight, and obesity as dependent variables and having fewer teeth (<20) and infrequent food intake as independent variables, with adjustment for potential confounders. Results Weight loss was associated with having fewer teeth (men: odds ratio [OR] 1.3; 95% confidence interval [CI], 1.2–1.3; women: OR 1.2; 95% CI, 1.1–1.3) and infrequent fruit/vegetable intake (men: OR 1.1; 95% CI, 1.1–1.2; women: OR 1.4; 95% CI, 1.3–1.5) and fish/meat intake (OR 1.2; 95% CI, 1.1–1.3 for both sexes). No interaction was observed between having fewer teeth and food intake. Obesity was associated with the same factors: having fewer teeth (ORs 1.2 and 1.3 for men and women, respectively) and infrequent intake of fruit/vegetables (ORs 1.1 and 1.2 for men and women, respectively) and fish/meat (OR 1.1 for both sexes). Infrequent fruit/vegetable intake showed a higher OR for underweight in women with fewer teeth than for others. Conclusions Having fewer teeth and infrequent food intake were associated with both weight loss and obesity. A significant interaction was observed in the associations of having fewer teeth and infrequent food intake with underweight in women.

Individual- and community-level social gradients of edentulousness

BackgroundCommunity-level factors as well as individual-level factors affect individual health. To date, no studies have examined the association between community-level social gradient and edentulousness. The aim of this study was to investigate individual- and community-level social inequalities in edentulousness and to determine any explanatory factors in this association.MethodsWe analyzed the data from the Japan Gerontological Evaluation Study (JAGES). In 2010-2012, 112,123 subjects aged 65 or older responded to the questionnaire survey (response rate = 66.3%). Multilevel logistic regression analysis was applied to determine the association between community-level income and edentulousness after accounting for individual-level income and demographic covariates. Then, we estimated the probability of edentulousness by individual- and community-level incomes after adjusted for covariates.ResultsOf 79,563 valid participants, the prevalence of edentulousness among 39,550 men (49.7%) and 40,013 women (50.3%) were both 13.8%. Living in communities with higher mean incomes and having higher individual-level incomes were significantly associated with a lower risk of edentulousness (odds ratios [ORs] by 10,000 USD increments were 0.37 (95% confidence interval [CI] [0.22-0.63]) for community-level and 0.85 (95% CI [0.84-0.86]) for individual-level income). Individual- and community-level social factors, including density of dental clinics, partially explained the social gradients. However, in the fully adjusted model, both community- and individual-level social gradients of edentulousness remained significant (ORs = 0.43 (95% CI [0.27-0.67]) and 0.90 (95% CI [0.88-0.91]), respectively). One standard deviation changes in community- and individual-level incomes were associated with 0.78 and 0.84 times lower odds of edentulousness, respectively. In addition, compared to men, women living in communities with higher average incomes had a significantly lower risk of edentulousness (p-value for interaction < 0.001).ConclusionsIndividual- and community-level social inequalities in dental health were observed. Public health policies should account for social determinants of oral health when reducing oral health inequalities.