The physiological influence of oral health on healthy ageing: a longitudinal analysis of two epidemiological cohort studies

In recent years there has been a dramatic increase in the proportion of older people (i.e., people aged 65 years and above) in the UK and other advanced countries. In the UK it is projected that by the year 2050 one in four people will be 65 years or above 65 years [1]. Advancement in medicine and knowledge in preventive care has led to prolonged life. However, aging is usually associated with chronic diseases and health conditions such as diabetes, chronic obstructive pulmonary disease, and dementia which can have a substantial impact on quality of life. The increasing aging population therefore has health and public health implications; it is a critical public health challenge to promote 'healthy aging'. Healthy aging refers to optimal physical and cognitive functioning, delayed onset of chronic diseases, and social wellbeing in older age [2]. Oral health is a critical component of overall health and therefore efforts to promote healthy ageing also need to recognise the burden of oral health in older people. Oral health conditions are the most widely prevalent health conditions, and their risks increase substantially with age, constituting a major burden of ill-health [3]. In a population-based study of older British men, 64% had few teeth (<21 teeth), 43% had active periodontal (gum) disease and over a third had dry mouth [4]. Replacement of teeth with dentures is also problematic in older people due to resorption of the alveolar bone and complications of denture stomatitis [5]. Oral diseases are also very costly, with an estimated global yearly direct cost of treatment (dental services) to be US$298 billion in 2010 [6]. and £3.4 billion/year in England[7].
Several studies have reported that oral health problems are associated with a number of health outcomes in older populations - such as, disability and physical function [8], frailty [9], cardiovascular diseases [10], mortality (Friedman 2016) and metabolic syndrome [11] - as well as with markers of chronic conditions, such as inflammatory, hemostactic and cardiac biomarkers [12].
Poor oral health has also been linked to diet and nutrition. Dry mouth and tooth loss influence chewing ability and food selection, leading to the avoidance of foods that are difficult to chew (fruit, vegetables, meat) resulting in poor diet and deficiencies in key nutrients [5]. However, replacement of teeth with dentures is also problematic in older people due to resorption of the alveolar bone and complications of denture stomatitis [5]. Some studies also report or suggest a two-way association between type 2 diabetes and poor oral health [13-15].
Despite the increasing risks and burden of oral health problems among older people, few studies have investigated the influence of oral health on health and wellbeing (chronic conditions and quality of life) longitudinally and as such the mechanisms through which oral health influence quality of life of older populations is not well established. [8] and [9] conducted a cross sectional analysis to determine the influence of poor oral health on key health measures. They found that poor oral health was associated with frailty [9], physical function and disability [8]. There is the need for a longitudinal analysis to help better understand the associations and the underlying pathways. This project will use large longitudinal datasets with a long follow up period to examine the physiological mechanisms underpinning the association between age related health conditions (includes chronic diseases, such as type 2 diabetes mellitus) and oral health markers, particularly dry mouth and denture wearing. A clear understanding of the underlying and mediating pathways will help to improve the health of aging population.