Chewing ability and associated factors in older adults in Germany. Results from GEDA 2019/2020-EHIS

The results from GEDA 2019/2020-EHIS show that 20.0% of adults from 55 years of age reported reduced chewing ability. Of these, 14.5% had minor difficulty and 5.5% had major difficulty. The international studies cited in the introduction provide prevalences that deviate from the present results [5‐26]. Reasons for this are, for example, differences in the considered age groups or differences in the operationalization of the indicator. The question used to determine chewing ability varied in the studies: The majority of them asked about chewing [5‐11, 13‐15, 17, 18, 20, 24], only a few, as in the present one, asked about chewing and biting [22, 29].

In the context of varying prevalences of oral health parameters between countries, socio-cultural aspects also play a role in influencing oral health, such as insufficient exposure to fluoride or difficult access to oral and dental care products [53]. Therefore, studies from Germany are particularly relevant for an interpretation of the present results. The German Oral Health Study from the Institute of German Dentists provides both survey data and clinical data on the oral health of the population in Germany [54]. In this study, data on the oral health of selected age groups are collected. According to the data from the fifth survey (2014), 31.3% of 65- to 74-year-olds had reduced chewing ability. In GEDA 2019/2020-EHIS, the corresponding figure is 18.8%. However, a direct comparison of the results is not possible, for example, due to the different question and answer categories. The question asked in the German Oral Health Study was “Do you have difficulty chewing solid food (e.g. fruit, bread, meat, etc.)?” with the response options “not at all”, “a little”, “partly”, “relatively strong” and “very strong/makes great difficulties” [54]. Even though the results are not directly comparable, both studies indicate a higher proportion of older adults who have reduced chewing ability. In a study examining the probability to bite and chew hard foods in older adults from 14 European countries, Germany was ranked 5th, i.e. in the upper midfield [55].

Factors associated with reduced chewing ability among women and men were old age, low SES, limitations to usual activities due to health problems, depressive symptoms, daily smoking, low dental utilization, and perceived unmet needs for dental care. Thus, the present results are in line with the above-mentioned international studies [5, 7‐11, 14‐17, 19, 23, 25, 26, 29]. The finding that more people are affected by reduced chewing ability with increasing age is supported by the fact that oral diseases and oral impairments, which in turn can lead to functional limitations such as chewing disability, occur more frequently with increasing age [56]. The social gradient observed in reduced chewing ability, which disadvantages individuals with low SES, is similarly evident in the occurrence of oral diseases and oral impairments [56]. Moreover, adults who smoke daily were more likely to have reduced chewing ability than non-daily smokers. Oral diseases and oral impairments are more common in smokers than in non-smokers, as smoking damages the oral cavity in many ways due to the pollutants contained in tobacco smoke [57]. People who did not visit a dental office in the year prior to the survey were, as expected, more likely to report reduced chewing ability than those with appropriate utilization. Regular dental visits can detect oral diseases at an early stage and suitable measures can be initiated to prevent oral impairments and functional limitations [58]. Beyond that, adults who stated that they needed dental care but could not afford it were more likely to have reduced chewing ability than those without such problems. Financial reasons are the most common cause why necessary dental treatments are not perceived [59]. In addition, the results illustrate a relationship between reduced chewing ability and limitations to usual activities due to health problems. In this context, one study indicated that older people who are still active tend to be more motivated to maintain their oral health and have less difficulty brushing their teeth and attending dental check-ups [7]. Additionally, older people who are still active are generally mentally fitter and thus better able to understand oral health-related information [7]. The results also suggest a relationship between reduced chewing ability and depressive symptoms as screened by the PHQ-8, which measures symptoms including depressed mood, decreased interest, fatigue, and loss of energy [45]. One possible explanation for this association could be that affected people are unable to take adequate care of their oral health due to their mental state [60]. Furthermore, studies show that chewing ability also influences food choices, which in turn can affect diet and body weight [7, 8, 22, 26]. In the present study, however, the association between reduced chewing ability and non-daily fruit and vegetable consumption and underweight, respectively, was significant only in the univariate but not in the multivariate model. The same applied to the association between reduced chewing ability and the utilization of home care services. In contrast, other studies suggest that reduced chewing ability is associated with lower self-care [5, 17]. In future, longitudinal studies focusing on the effect of the considered characteristics on chewing ability are required to show possible causal relationships [25].

The present analyses point to prevention potentials and healthcare needs. In order to develop tailor-made prevention measures, it is important to identify vulnerable groups. According to the results, especially people from 75 of age and those with low SES reported reduced chewing ability. In addition, the results show that daily smoking is associated with reduced chewing ability. Dentists play an important role in communicating recommendations for health behavior change to improve or maintain oral health [57, 61]. This includes giving information on regulations on co-payments and fixed allowances for dental treatments in an understandable way. It is important that co-payments for dental treatment can be financed in order to address unmet needs for dental care and eventually reduce social inequalities in oral health [59]. In Germany, people with statutory health insurance who have at least one dental check-up a year have lower co-payments. The finding that people without annual dental visit more often had reduced chewing ability leads to the question of how these people can be better reached. General practitioners could contribute to this by motivating their patients to visit the dental practice more often [56, 62]. The same applies to home care services, which should encourage and help their patients to visit the dentist regularly [56]. An expert standard for the promotion of oral health in nursing care was recently published in Germany [63]. Beneficial outcomes of home visiting programs in order to maintain health and autonomy of older individuals were reported inconsistently in literature, either reporting reduction of disability burden [64], or no health effects at all [65]. Adversely, oral health care programs may contribute to an improvement of daily activities in older patients requiring home nursing care, by recovering or maintaining dental health or occlusal support by preventing tooth loss [66, 67]. In Germany, the AuB-concept was founded in 2010 by the Federal Dental Association and the Federation of Panel Dentists [68]. This concept was the first to systematically address the care of vulnerable patient groups who usually have poorer oral health compared to the general population like older immobile individuals, and people with disabilities. This concept led to new billing codes as additional remuneration for the required outreach to insured persons by the Statutory Health Insurance Structure Act, which came into force in 2012, thus enabling professional oral health care for home care recipients or nursing home residents by dentists, working in private practices. A comprehensive community-based oral health care by public health dentists, who are working in community health authorities, is not yet a mandatory task in Germany.

A study on the relationship between childhood circumstances and chewing ability in adulthood was able to show that socioeconomic and behavioral factors in childhood have lasting effects on chewing ability in middle and later adulthood [69]. This underlines the importance of regular prevention interventions that start early to promote oral health and oral health behavior [70, 71]. Here, special attention should be paid to individuals from socially disadvantaged backgrounds because they are more likely to have an unhealthy lifestyle (e.g. daily smoking) [48] and they have a lower control-oriented dental utilization than those of middle and high SES [72, 73]. Maintaining dental health in childhood is of great importance because damage to permanent teeth is irreversible and affects oral health in all following life stages [74]. Due to their extensive preventive programs and their outreach care in nursing and elementary schools as well as in colleges, community-based Public Dental Health Services in Germany have a crucial impact concerning the amelioration of population-based dental health care measures, by empowering children to perform an adequate oral hygiene, in order to maintain their teeth healthy, independently from their social background [75]. Thus, the strengthening of Dental Public Health measures in childhood might be a useful step towards an increase in social justice and equal health opportunities in Germany, eventually benefiting all age groups into high adulthood.

The present study has some strengths and limitations that need to be discussed. This article is the first to comprehensively analyze the chewing ability, including associated factors, in older people based on data from a sample representative of the population in Germany. The high number of participants in GEDA 2019/2020-EHIS allows stratification according to various characteristics and thus a detailed examination of chewing ability in selected subgroups. However, participation rates in older people are lower compared to the general population, and persons affected by health limitations are less likely to participate in health surveys [76, 77]. Beyond that, people living in residential facilities or nursing homes were not included in the survey. This can result in selective non-participation and consequently under-representation and bias of the results (selection bias) [78]. Regarding the indicator on utilization, which asks about dental and orthodontic visits, it should be noted that in Germany orthodontic treatment is not a standard treatment in adulthood. Statutory health insurance covers dental visits, but orthodontic treatment only up to the age of 18 and merely from a certain degree of severity [79]. It can therefore be assumed that participants reported almost exclusively dental visits. In addition, this article was able to show that reduced chewing ability is associated with self-reported unmet needs for dental care. However, it is unclear what kind of dental treatment the respondents could not afford. This would be important information, as in Germany the amount of costs for these treatments can certainly vary [80]. Moreover, it is important to note that functional limitations such as reduced chewing ability are an integral component of the broader concept of oral health-related quality of life (OHRQoL) [81] that can be assessed, for example, with the OHIP-5 (Oral Health Impact Profile) [82]. As mentioned in the introduction, international studies indicate a strong relationship between chewing ability and OHRQoL [9, 20, 24, 27, 28]. In GEDA 2019/2020-EHIS, no information on OHRQoL is available. Therefore, corresponding analyses are still pending for Germany.

Chewing, as well as mastication, were often used as synonyms in literature for the procedure of processing food during dietary intake [83‐87]. The Glossary of Prosthetic Terms defines mastication ‘as the process of chewing food for swallowing and digestion’ [88]. Based on this definition, chewing may be considered as one active element among others, which are subsumed under the umbrella term ‘mastication’. The ability to process food properly may be impaired by a multitude of parameters, including chewing, eating and saliva disorders, deterioration of oral motor skills, the oral health status, or oral pain, as published in a systematic review [89]. In this publication, masticatory dysfunction was subsumed under the generic term ‘deterioration of oral motor skills’, while chewing difficulties were classified under ‘chewing, eating and saliva disorders’, thus displaying a clear separation between the terms ‘chewing difficulties’ and ‘masticatory dysfunction’. Again, this insight may be seen as a further example for a current lack of consensus among researchers on the exact classification or use of semantics concerning the terms ‘mastication’ and ‘chewing’, as stated in literature [90]. In order to simplify the decision on the correct terminology, and due to the obviously homologous use of both terms in a certain number of publications, as well as with respect to the wording of the questioning in the survey, the term ‘chewing ability’ was used in the present publication.