Progress of multimorbidity among older adults and the role of Oral Health

Abstract

The world's ageing population has rapidly increased because of the demographic shift that has occurred over the last several decades. Multimorbidity is one of the most significant effects of the ageing population on public health. When a person has more than two chronic conditions, this is known as multimorbidity. Furthermore, multimorbidity is common, increases with age, and is more prevalent in those from lower socioeconomic backgrounds, according to all current studies. Multimorbidity is linked to worse outcomes such as lower quality of life, increased mortality, polypharmacy, high treatment burden, higher rates of adverse drug events, and much higher use of health services, including emergency hospital admissions. The mechanism of multimorbidity development is a multifactorial dynamic process, oral health could be associated with multimorbidity through different pathways. One of the most plausible pathways is the impact of poor oral health on nutritional status. Aim: The thesis aimed to explore socioeconomic inequalities in the progress of multimorbidity, among older adults. The second aim is to assess whether tooth loss is associated with the progress of multimorbidity. The objectives of the thesis were to (1) examine socioeconomic inequalities in the progress of multimorbidity among older adults in the U.S.A. (2) Assess whether tooth loss is longitudinally associated with the progress of multimorbidity and (3) explore the nutritional pathway between tooth loss and the progress of multimorbidity. (4) Examine the relationship between allostatic load and the progress of multimorbidity and whether it mediates socioeconomic inequalities in multimorbidity. Methods: Seven waves were used (2006-2018) of the Health and Retirement Study, a longitudinal survey of older Americans. Multimorbidity was indicated by self-reported diagnosis of 5 conditions: diabetes, heart conditions, lung diseases, cancer, and stroke. Socioeconomic indicators were ethnicity, education, wealth, and income. Behavioural factors were smoking, excessive alcohol consumption, physical activity, and body mass index. Allostatic load was used as a biomarker of stress and was indicated by high-density lipoprotein, glycosylated haemoglobin, c-reactive protein, waist circumference, and high blood pressure. Nutritional intake was calculated in 2013 by summing 10 nutrients (Protein, Vitamins C, D, B12, E, Calcium, Zinc, Polyunsaturated fatty acids, Folate and ß- carotene). Finally, edentulism (total tooth loss) was assessed in three waves (2006, 2012, and 2018). Multilevel models for the analysis of longitudinal data were used to assess the association between socioeconomic factors and multimorbidity and whether behavioural factors mediate this association. Multilevel models were used to examine the relationship between oral health and multimorbidity and whether nutritional intake mediates this association. The association between allostatic load as a marker of chronic stresses with progress of multimorbidity was also assessed using multilevel models for longitudinal panel data. Results: Socioeconomic indicators showed different significant associations with the progress of multimorbidity demonstrating social gradients. However, after adjusting for behavioural factors these associations were attenuated. Incidence rate ratios (IRR) of multimorbidity was considerably higher in those who did not finish high school (IRR 1.21; 95% CI 1.18, 1.23) compared to those who attended college. After adjusting for behaviours, IRR decreased to 1.11 (95% CI 1.07, 1.14). Furthermore, IRR of multimorbidity was greater in the lowest quartiles of total wealth and income, with IRR 1.47 (95% CI 1.44, 1.51) and 1.25 (95% CI 1.22, 1.28), respectively. These IRRs decreased to 1.31 (95% CI 1.26, 1.36) and 1.22 (95% CI 1.18, 1.27), respectively, after accounting for behaviours. Moreover, longitudinal associations were found between edentulism in the years 2006 and 2012 and the progress of multimorbidity. After adjusting for behavioural factors, and total nutrients, the IRR for multimorbidity among edentate individuals was 1.12 (95%CI 1.06, 1.18) and 1.10 (95%CI 1.05, 1.16) in 2006 and 2012, respectively. Moreover, the analysis showed an association between edentulism (in 2006 and 2012) and total nutrition (2013) adjusting for age and gender. Total nutrients in 2013 were lower among those who were edentate in 2006 [IRR 0.97 (95%CI 0.95, 0.99)] and in 2012 [IRR 0.98 (95% CI 0.96, 0.99)]. A positive association was found between allostatic load and multimorbidity even after accounting for socioeconomic and behavioural factors. Conclusion: This thesis illustrated that socioeconomic factors were associated with the progress of multimorbidity, and behavioural factors appeared to mediate the association. It also demonstrated that the association between socioeconomic factors and multimorbidity was slightly attenuated after adjusting the allostatic load. Additionally, the allostatic load was significantly associated with multimorbidity even after accounting for socioeconomic and behavioural factors. Moreover, edentulism in 2006 and 2012 showed a statistically significant association with multimorbidity, although. The association between total nutrition and multimorbidity was significant only in the unadjusted models.