Background Difficulties in communication due to vision, hearing and tooth loss have a serious impact on health. We compared the association between and attribution of each of these factors on social interaction.
Methods This cross-sectional study examined data from the 2016 Japan Gerontological Evaluation Study (n=22 295) on community-dwelling people aged ≥65 years in Japan. The dependent variable was the frequency of meeting friends as a measure of social interaction, and less-than-monthly was defined as fewer social interactions. The independent variables were self-reported degrees of vision, hearing (5-point Likert scale) and tooth loss (five categories), with ‘poor’ or ‘0 teeth’ defined as the worst category. Sex, age, educational attainment, comorbidity and residential area were used as covariates. Poisson regression analysis with multiple imputations was used to estimate the prevalence ratios (PRs) of fewer social interactions by each status. Subsequently, the population attributable fraction (PAF) was calculated to assess the public health impact.
Results The number of participants with fewer social interactions was 5622 (26.9%). Proportions of fewer social interactions among those with the worst vision, hearing and number of teeth categories were 48.7%, 40.1% and 32.0%, respectively. Their corresponding PRs of fewer social interactions were 1.72 (95% CI 0.97 to 3.05), 1.35 (95% CI 0.99 to 1.85) and 1.23 (95% CI 1.10 to 1.37), respectively. The total PAF for vision, hearing and number of teeth was 8.3%, 5.0% and 6.4%, respectively.
Conclusion Self-reported vision, hearing and tooth loss were associated with fewer social interactions. The magnitude of these impairments was largest in vision, followed by tooth and hearing loss.
- Dental health
- Social activities
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Difficulties in communication due to vision, hearing and tooth loss have a serious impact on the health of older people. Previous studies have indicated that vision, hearing and tooth loss are associated with falls,1 2 cognitive decline,3 reduction in social participation4–6 and mortality.7 8 Vision, hearing and tooth loss are conditions that are also associated with ageing, and these conditions are prevalent among older people. The WHO estimates that 81% of those aged ≥50 years have vision loss9 and that one-third of people aged ≥65 years are affected by a disabling hearing loss.10 In terms of oral health, more than one-tenth of people aged ≥60 years are affected by severe tooth loss.11 The prevalence of vision, hearing and tooth loss increases with age.12–14 Therefore, when estimating their burden, a study in an ageing society, such as Japan, is relevant. In Japan, the percentage of people aged ≥65 years was 28.0% in 2019, which is the highest in the world.15
In addition to their functions, vision, hearing and number of teeth have important social interaction roles, and social isolation increases the risk of disease and mortality. Older people with difficulty in communicating due to impairments in vision and hearing and a reduction in the number of teeth are at significant risk for social isolation as these impairments cause difficulties in performing activities of daily living (ADL)3 16 and instrumental activities of daily living (IADL).17–19 Social isolation has been found to increase the risk of coronary heart disease,20 depressive symptoms,21 cognitive impairment22 and mortality.23
Prevalence of social isolation in this ageing world is an emergent health policy issue. Social isolation is measured by the number of interactions with family and friends and participation in volunteering groups or hobby groups.22 In recent years, policies aimed at reducing loneliness have been established, such as the appointment of the First Minister for Loneliness in the UK in 2018.24 The prevalence of social isolation was estimated at 17% among older adults in the USA.25 In the UK, older people with severe social isolation were estimated at approximately 1.3 million.26 Social isolation is also an issue among older people in Japan, and local governments have promoted community intervention programmes aimed at maintaining social interactions.27 Reducing social isolation is an important public health concern to reduce not only the burden of cost for medical care but also to improve the quality of life among older people. Although vision, hearing and tooth loss increase the risk of social interaction, no study has compared the degree of the effects of these impairments on social isolation. This study aimed to compare the impact of vision, hearing and tooth loss on social interaction among older people.
Setting and participants
This cross-sectional study examined the 2016 wave of the Japan Gerontological Evaluation Study (JAGES) Project data28 and was conducted between September 2016 and January 2017. The JAGES is a longitudinal cohort study directed at understanding the health, social and behavioural issues among the older population in Japan. To date, the self-reported questionnaire surveys were conducted in four waves: 2003, 2006, 2011, 2013, and 2016. The subjects of the JAGES 2016 wave were community-dwelling independent people aged ≥65 years without eligibility for the benefits of long-term public care insurance in 39 municipalities in Japan. These municipalities were not randomly selected as the survey was conducted in collaboration with local municipalities. However, the target population was randomly selected, or, in small municipalities, the entire population was targeted. Self-administered questionnaires, including oral health items, were posted to 279 661 targeted individuals, and 180 021 people responded (response rate=70.2%). The survey questionnaire consisted of core and non-core items. Core items were distributed to all targeted populations. There were eight modules of non-core items, and people randomly received one module with the core items. Wave 2016 contained questions regarding vision and hearing loss in one module of the non-core items, and 22 295 people responded to this questionnaire. In this study, we focused on people living independently. The 2839 participants who answered ‘needs care or assistance in daily life’ or did not respond to this questionnaire were excluded. Finally, 19 456 participants were included in our analysis. In JAGES 2016, responses to the questionnaire by another person on behalf of the targeted individual were allowed when the individual could not read or write.
The study protocol was approved by the Ethics Committee of the National Center for Geriatrics and Gerontology (No. 992) and the Ethics Committee of Chiba University (No. 2493). In this study, the questionnaire was sent by mail, along with an explanation of the study, and the participants read it and replied. Informed consent was provided by those who replied and returned the questionnaire.
The dependent variable was the frequency of meeting friends as a measure of social interaction. Participants were asked to select an answer regarding the frequency of meeting with their friends from the following six options: ‘more than four times a week’, ‘two or three times a week’, ‘once a week’, ‘one to three times a month’, ‘several times a year’ and ‘not meeting my friends’. This variable was dichotomised; the frequency of meeting friends ‘several times a year’ and ‘not meeting my friends’ was defined as fewer social interactions.
The independent variables were the degree of vision loss and hearing loss and the reduction in the number of teeth. The degree of vision and hearing loss was determined using a 5-point Likert scale. To determine self-reported vision and hearing loss, respondents were asked the following questions: please tell us your vision/hearing status. If you wear a vision/hearing aid, what is the response when you use it. The choices were (1) excellent, (2) very good, (3) good, (4) fair or (5) poor. To determine the self-reported number of natural teeth, respondents were asked as follows: please tell us the number of natural teeth you currently have. The choices were ‘≥20 teeth’, ‘10–19 teeth’, ‘5–9 teeth’, ‘1–4 teeth’ and ‘0 teeth’.
In addition, we used the number of impairments as an independent variable to investigate the association of fewer social interactions on having multiple impairments. This was the sum of vision, hearing and tooth loss. For this, ‘poor’ or ‘0 teeth’ were defined as the worst state, and the worst responses were counted. As regards multiple impairments, people were categorised into three groups: people without impairment, people with one impairment and people with two or more impairments (as there was only one person with a triple impairment).
The covariates were sex, age, educational attainment, medical history, depression status, degree of urban residence and denture usage. Denture usage was used as a covariate only when analysing the number of teeth. Age was considered as a continuous variable. Education attainment was determined by self-reported years of schooling. The choices for this question were <6, 6–9, 10–12 and ≥13 years. Because the number of responses for the ≤6-year category was small, it was integrated into the ≤9-year category. Medical history was queried as follows: please respond regarding the illness that is currently being treated or is a sequela. The participants responded regarding the relevant illness, including stroke, diabetes, heart disease, cancer, respiratory disease and arthritis, with a ‘yes’ or ‘no’. Depression status was defined by the scores on the Geriatric Depression Scale (GDS)-15 (GDS <5: non-depressive, GDS ≥5: depressive). The degree of urban residence was categorised into three types according to population density as urban, semiurban and rural areas, defined as ≥1500 people/km2, 1500–1000 people/km2 and <1000 people/km2, respectively.
We applied Poisson regression as the prevalence of fewer social interactions was higher, and the OR estimated by logistic regression overestimates the association.29 First, Poisson regression analysis was used to calculate the adjusted prevalence ratios (PRs) and 95% CIs of fewer social interactions by the degree of vision and hearing loss and the number of teeth. Variables for vision, hearing, teeth and the number of impairments were included separately in the models. We used multiple imputation by chained equations to account for bias due to missing values in the models. All variables included in the analyses were used for multiple imputation. Online supplemental table S1 shows the number and percentage of missing responses for each variable used in the multiple imputation. We assumed data to be missing at random and created 20 multiple imputed data sets. In the analysis, data on 22 295 participants were included. The data were analysed using the STATA MP version 15.0 (Stata Corp., College Station, Texas, USA).
Supplementary file 1
Second, based on the results of the Poisson regression, the population attributable fraction (PAF) of vision, hearing and tooth loss to fewer social interactions was calculated to assess the public health impact of social interactions. The PAF is defined as the estimated fraction of a population’s morbidity that would not have occurred if there had been no exposure.30 In this study, the PAF was estimated from the adjusted PR for each exposure, vision, hearing and the number of teeth, and the prevalence of exposure among cases (pc) using the following formula: PAF=pc(1−1/PR).30 PAF indicates the percentage of people with fewer social interactions due to vision, hearing or tooth loss. If they did not have these impairments, they would not have experienced fewer social interactions.
PRs were calculated when the best status was used as the reference category. However, there is a possibility that the values for vision, hearing and tooth loss are different. Therefore, we calculated the PAF using different reference categories in the sensitivity analysis. For this reference category, excellent and very good were combined for vision and hearing, and 1–4 teeth and 0 teeth were combined for teeth as model 1. In model 2, excellent, very good and good were combined for vision and hearing, and 5–9 teeth, 1–4 teeth and 0 teeth were combined.
Table 1 shows the basic characteristics of the participants by social interaction with multiple imputation. The number of participants with fewer social interactions was 5622 (26.9%). Among the total participants, in terms of vision, there were 1888 (9.0%) participants with ‘excellent’ vision, 6029 (28.9%) with ‘very good’ vision, 11 265 (54.0%) with ‘good’ vision, 1656 (7.9%) with ‘fair’ vision and 29 (0.1%) with ‘poor’ vision. In terms of hearing, there were 4200 (20.1%) participants with ‘excellent’ hearing, 6156 (29.5%) with ‘very good’ hearing, 7834 (37.5%) with ‘good’ hearing, 2566 (12.3%) with ‘fair’ hearing and 111 (0.5%) with ‘poor’ hearing. In terms of number of teeth, there were 11 415 (54.7%) participants with ‘≥20 teeth’, 4470 (21.4%) with ‘10–19 teeth’, 2016 (9.7%) with ‘5–9 teeth’, 1275 (6.1%) with ‘1–4 teeth’ and 1691 (8.1%) with ‘0 teeth’.
Table 2 shows PRs and 95% CIs of vision, hearing and number of teeth on fewer social interactions with multiple imputation analyses. The risk of decreasing social interaction was significantly higher in people with visual, hearing and tooth loss. Participants with poorer vision, hearing or number of teeth tended to have higher PRs for having fewer social interactions. The adjusted PRs for the ‘fair’ vision and hearing and ‘1–4 teeth’ categories were 1.22 (95% CI 1.07 to 1.39), 1.12 (95% CI 1.02 to 1.24) and 1.30 (95% CI 1.16 to 1.45), respectively. The adjusted PRs for the ‘poor’ vision and hearing and ‘0 teeth’ categories were 1.72 (95% CI 0.97 to 3.05), 1.35 (95% CI 0.99 to 1.85) and 1.23 (95% CI 1.10 to 1.37), respectively. The adjusted PRs for one impairment and two or more impairments were 1.11 (95% CI 1.02 to 1.22) and 1.70 (95% CI 0.97 to 2.96), respectively, compared to without impairment. Having multiple losses had a greater association with fewer social interactions than did having a single loss.
Figure 1 shows the PAF for fewer social interactions according to vision, hearing and tooth loss. The total PAF for vision, hearing and number of teeth not being ‘excellent’ or ‘20 teeth’ were estimated to be 8.3%, 5.0% and 6.4%, respectively. They were equivalent to the avoidance of having fewer social interactions by preventing vision, hearing and tooth loss in 83, 50 and 64 persons per 1000 cases, respectively. Online supplemental table S2 shows details of the PAFs and 95% CIs shown in figure 1. Among the three variables, impairment of vision exhibited the greatest association with social interaction. When using different reference categories, the PAF for vision was also the largest (online supplemental table S3).
The present study revealed that vision, hearing and tooth loss were independently associated with a low frequency of social interactions among community-dwelling older adults. The magnitude of these impairments on social interactions was largest in vision, followed by tooth and hearing loss. From a public health viewpoint, by PAF, hearing and tooth loss also had a substantial impact on the populations. Multiple losses had a greater association with fewer social interactions than a single loss.
There have been consistent results in previous studies that have shown the association between vision, hearing and tooth loss and social interaction. Self-reported vision loss was independently associated with reduced social participation such as a family or friendship activity, physical activity or volunteer work, in Japan and Canada.4 17 Self-reported hearing loss was also associated with social inactivity in older Europeans.31 Poor oral health is considered to cause difficulty in eating and speaking and decrease social participation.5 A cohort study reported that tooth loss was a predictor for becoming homebound among older Japanese individuals.6 Additionally, a previous study that compared the impact of vision and hearing loss on social inactivity reported a greater impact for vision loss than hearing loss.31 However, although eyes and ears are necessary organs for communication with others, no study included oral health.
Our study adds new findings and gives new implications. At first, oral health played an important role in social interaction as well as eyes and ears. This study also showed the difference between the impact on individuals and populations regarding vision, hearing and tooth loss. Vision, hearing and tooth loss have been shown to cause difficulties in performing ADL and IADL, respectively.3 16–19 Therefore, these impairments seem to decrease social interaction. The impact of vision loss could have been the largest PR for individuals at risk of having fewer social interactions because the eyes are supplying an estimated 80% of our information regarding the outside world.32 In addition to these impacts on individuals, this study also shows the impacts on the population. From a public health viewpoint by PAF (figure 1), hearing and tooth loss also had a substantial impact on populations. In particular, because oral diseases show the highest prevalence among diseases and health conditions,11 public health districts should consider its population-level impact as well as its individual-level impact. The burden of disease due to vision, hearing and tooth loss on society is likely to increase in an ageing society. Vision, hearing and tooth loss are preventable and treatable.9 10 Therefore, interventions aimed at these losses may become important measures for improving social interaction among older people.
The present study has several strengths and limitations. As a strength, this study was the first to compare the association of three functions on social interactions. In addition, it calculated the PAF for each function, which has useful public health implications. There were several limitations to this study as well. First, it can be presumed that the PAF of vision loss was underestimated. Participants who had vision loss were less likely to answer the questionnaire, although response to the questionnaire by other people on behalf of the targeted individual was allowed, especially when the individual could not read or write. Therefore, the prevalence of vision loss may be estimated to be lower. Second, the causal association between functional impairment and social interaction could not be concluded because this is a cross-sectional study. However, it is difficult to assume that decreasing social interaction leads to a decrease in the functional degree of visual and hearing. On the other hand, regarding oral health, a previous study suggested that social participation was associated with a reduced risk of tooth loss in a longitudinal study.33 These results suggest bidirectional relationships between social participation and oral health. It is essential that the causal association between functional impairment and social interaction must be clarified in a longitudinal study. Third, there is the possibility of misclassification due to the use of a self-reported questionnaire. However, the validity of this measure has been established. Self-reported vision, hearing and tooth loss were associated with objective measurement.34–36 Finally, this study compared the three different statuses by PR and PAF to examine the individual-level and population-level impacts on social interaction. However, the results should be carefully interpreted because the expectation of having excellent vision, hearing and oral health is different, and so the selection of one of the five response categories on our questionnaire would be different among people with different statuses. This results in a difference in the distribution of the worst status. Therefore, we calculated the PAF using different categories (online supplemental table S3). As a result, the overall trends were consistent.
What is already known on this subject
Vision, hearing and tooth loss affect social interactions, which increase the risk of disease and mortality among older people.
A previous study compared the impact of vision and hearing loss on social inactivity and reported that vision loss has a greater impact than hearing loss.
No study has neither estimated the population-level impact of these factors nor included oral health.
What this study adds
The present study revealed that vision, hearing and tooth loss were associated with a lower frequency of social interactions among community-dwelling older adults.
Although vision loss had the largest individual-level impact, hearing and tooth loss also showed a substantial population-level impact, estimated by the population attributable fraction, as their prevalence was higher than vision loss.
Contributors AI participated in the study design, performed the statistical analysis and drafted the manuscript as the principal author. JA conceived the study concept, participated in the acquisition of data and study design, performed analysis and interpretation of data, and edited the manuscript. KO, TY and YH participated in the study design and critically revised the manuscript. KK is the principal investigator of the JAGES project and helped develop the idea for the study, performed interpretation of data and critically revised the manuscript. All authors read and approved the final manuscript.
Funding This study used data from the Japan Gerontological Evaluation Study (JAGES), which was supported by JSPS (Japan Society for the Promotion of Science) KAKENHI (grant numbers; 15H01972, 15H04781, 15H05059, 16H05556, 25253052, 18H03018, 18H04071, 18H03047, 18H00953, 18KK0057, 19H03915, 19H03860, 19K04785, 20H00557), Health Labour Sciences Research Grant (H28-Choju-Ippan-002, H29-Chikyukibo-Ippan-001, 18H04071, 19FA2001), Japan Agency for Medical Research and Development (AMED) (JP17dk0110017, JP18dk0110027, JP18ls0110002, JP18le0110009, JP20dk0110034, JP20dk0110037, 20dk0310108), Open Innovation Platform with Enterprises, Research Institute and Academia (OPERA, JPMJOP1831) from the Japan Science and Technology (JST), a grant from Innovative Research Program on Suicide Countermeasures (1-4), a grant from Sasakawa Sports Foundation, a grant from Japan Health Promotion and Fitness Foundation, a grant from Chiba Foundation for Health Promotion and Disease Prevention, the 8020 Research Grant for fiscal 2019 from the 8020 Promotion Foundation (19-2-06), a grant from Niimi University (1915010), grants from Meiji Yasuda Life Foundation of Health and Welfare and the Research Funding for Longevity Sciences from National Center for Geriatrics and Gerontology (29-42, 30-22).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.
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