Takashi Ohi

Hypermethylation of CpGs in the Promoter of the COL1A1 Gene in the Aged Periodontal Ligament

Although the human periodontal ligament shows age-associated histological alterations, the molecular mechanisms are not yet understood. We previously found that COL1A1 gene expression declines with age. In this study, we asked whether DNA methylation in the regulatory region of the gene alters in the aging process, as a possible cause of the decline. The method used was a bisulfite modification of cytosine and nucleotide sequencing of DNA. While the 1st intron region was kept demethylated at young and old ages, the levels of methylation at most CpG sites in the proximal and distal regions of the promoter showed elevation at older ages. Analysis of the data indicates the possible importance of DNA hypermethylation in the promoter region for the age-associated decrease of COL1A1 gene expression.

Association Between Tooth Loss, Receipt of Dental Care, and Functional Disability in an Elderly Japanese Population: The Tsurugaya Project

To examine whether number of remaining teeth and regular dental care affect incident functional disability in elderly Japanese adults.

Relationship between status of dentition and incident functional disability in an elderly Japanese population: prospective cohort study of the Tsurugaya project

PURPOSE The purpose of this study was to examine whether the status of dentition is associated with incident functional disability in elderly people. METHODS This prospective cohort study targeted community-dwelling Japanese adults of age ≥70 years (n=838). Participants were classified into the following four groups in accordance with Miyachis Triangular Classification, which represents the status of dentition on the basis of numbers of remaining teeth and occlusal supports: Zone A, ≥10 occlusal supports; Zone B, 5-9 occlusal supports; Zone D, ≤4 occlusal supports and ≥11 remaining teeth and Zone C, ≤10 remaining teeth. Incident functional disability was defined by the first certification of long-term care insurance in Japan. Data regarding age, sex, body mass index, medical history, smoking, alcohol consumption, education, depressive symptoms, cognitive impairment, social support, history of fall, and subjective masticatory ability were collected. RESULTS During follow-up for 5185 person-years, 305 participants experienced functional disability. Considering the follow-up data of  ≥3 years from baseline, participants in Zones C (hazard ratio [HR], 1.98; 95 % confidence interval [CI], 1.26-3.11) and D (HR, 2.50; 95 %CI, 1.54-4.05) were found to be more likely to develop functional disability than those in Zone A (p for trend=0.002). CONCLUSIONS Status of dentition was associated with incident functional disability in an elderly Japanese population. The findings of this study suggest that maintenance of remaining teeth and retention of occlusal supports contribute to the prevention of functional disability.

Maximum Occlusal Force and Incident Functional Disability in Older Adults: The Tsurugaya Project:

The purpose of the current study was to investigate the association between maximum occlusal force, which is an objective predictor of masticatory performance, and incident functional disability in an elderly Japanese population. A prospective cohort study was conducted targeting 815 (51.7% female) community-dwelling older adults aged ≥70 y residing in the Tsurugaya district, Sendai, Japan. The outcome measurement was incident functional disability, defined as a first certification of long-term care insurance in Japan, which is determined on the basis of a strictly established, uniform, nationwide standard. During a median follow-up of 7.9 y (interquartile range, 4.8–7.9 y), information on long-term care insurance was obtained from the Sendai Municipal Authority. Bilateral maximum occlusal forces of the participants were measured using a horseshoe-shaped pressure-indicating film, and the participants were categorized into quartiles based on occlusal force. Adjusted hazard ratios for functional disability were estimated with Cox proportional hazard models, adjusted for age, sex, body mass index, medical history, smoking status, alcohol consumption, duration of education, depressive symptoms, cognitive impairment, physical functioning, marital status, history of falls, and number of remaining teeth. The multiple-adjusted hazard ratios and 95% confidence intervals (CIs) for incident functional disability compared to the greatest occlusal force quartile were 1.53 (95% CI, 1.02–2.33), 1.64 (95% CI, 1.06–2.55), and 1.64 (95% CI, 1.01–2.68) for the third, second, and first quartiles, respectively (P for trend = 0.011). A lower maximum occlusal force was significantly associated with an increased risk of functional disability independently of possible confounders, including the number of remaining teeth. Occlusal force may be a useful indicator of the relationship between oral function and geriatric health. Knowledge Transfer Statement:This prospective cohort study demonstrated that lower maximum occlusal force was associated with an increased risk of functional disability in older adults, even after adjustment for possible confounding factors, including the number of remaining teeth. This strengthens the rationale regarding the association between oral function and geriatric health. Particularly in older adults, occlusal force is reduced by several factors other than tooth loss, such as the absence of a dental prostheses, sarcopenia in the masticatory muscle, poor periodontal condition, and orofacial pain. Our findings suggest that maximum occlusal force may be a useful biomarker associated with diverse parameters aside from the number of remaining teeth.

Relationship of Periodontal Disease and Tooth Loss to Glucose Metabolism Disorder: The Ohasama Study

The purpose of this study was to examine the association of periodontal disease and tooth loss with glucose metabolism disorder. Cross-sectional data on 507 individuals aged ≥55 years old were obtained from the general population of Ohasama, a rural community in Japan. Periodontal status was examined using probing depth (PD) and clinical attachment loss (CAL). Subjects with at least 10 teeth were divided into two groups based on mean PD and CAL, with cut-off of 2.0 mm and 2.5 mm, respectively. The other subjects with 0–9 teeth were defined as multiple tooth loss group. Glucose metabolism disorder was defined as serum glycosylated hemoglobin (HbA1c) level of at least 5.8% and/or the use of medication for diabetes. Multivariate logistic regression analysis indicated that CAL ≥ 2.0 mm and multiple tooth loss were independently associated with the presence of glucose metabolism disorder. Our results suggest that a history of periodontal disease assessed by CAL and multiple tooth loss may be associated with an increased risk of glucose metabolism disorder.

Relationships Between Oral Health-Related Quality of Life and the Patterns of Remaining Teeth in the Middle-Aged and Elderly

The aim of this study was to investigate the relationship between oral health-related quality of life (OHRQoL) and the patterns of remaining teeth in different age groups. A total of 512 independent community-dwelling people (age: 68.0 ± 7.0, female: 65.9%) in Ohasama participated in this study. Subjects were divided into four categories by the patterns of remaining teeth and divided into three age groups (≤65 years, 66–71 years, ≥72 years). To evaluate OHRQoL, the Oral Impacts on Daily Performances (OIDP) scale was administered. According to the result of multiple regression analyses, in all age groups, the patterns of remaining teeth had significant associations with OHRQoL. Correlations appeared to be stronger between the patterns of remaining teeth and OHRQoL in the elderly group than in the middle-aged group. These results suggest that the maintenance of occlusal support and tooth retention are important to maintain quality of life levels later in life.