Abstract
Oral health is important to overall health, yet it remains unclear whether poor childhood oral health is associated with future adult health. This thesis aimed to investigate whether childhood dental caries experience could be a useful marker of ill-health in adulthood, by examining associations between primary dentition at age 5 years and poorer self-reported health, physical health, mental health and ageing in midlife.
Participants were members of two ongoing Aotearoa New Zealand birth cohort studies: The Dunedin Multidisciplinary Health and Development Study, and The Christchurch Health and Development Study (hereafter referred to as the Dunedin and Christchurch Studies). Both cohorts are population-based samples that have been repeatedly assessed at multiple time points from birth to the fifth decade of life (to age 40 years for the Christchurch, and to age 45 years for the Dunedin studies, respectively). Data on childhood caries experience and adult self-reported health, physical health and ageing, and mental health were used in the five studies (Chapters 4 to 8) that comprise the empirical chapters of this thesis.
Chapter 4 presented oral health findings among 5-year-old children from the Dunedin and Christchurch cohorts. Gradients in caries experience by community water fluoridation (CWF), socio-economic status (SES) and maternal education were observed, and despite the caries decline observed in Aotearoa New Zealand over the decades, a considerable proportion of children experience socioeconomic disadvantage and higher rates of dental caries. Among the proportion of children that experience caries nowadays, dmft scores resemble those of the children in these two birth cohorts back in the 70s-80s.
Findings from Chapter 5 showed that 5-year-olds who were caries-free were more likely to have ‘Excellent’ self-reported health by ages 40 and 45 years than those who have had caries. In addition, Dunedin study findings suggested that poor parental ratings of their own or their child’s oral health were associated with poorer self-reported general health by midlife.
Using Dunedin Study data, Chapter 6 described six distinctive dental caries experience patterns or trajectories across the lifecourse, assessed from ages 9 to 45 years. One low-, two moderate- and three high-caries-rate trajectories emerged from the data describing the different ‘dental life pathways’ that participants have followed by midlife. Early-life risk factors associated with those trajectories included higher dmfs scores at age 5 years, lack of exposure to CWF during the first five years of life, lower childhood cognitive function or IQ (intelligence quotient)—measured as a continuous score—and low childhood SES. Beyond clinical dental measures (dmfs), children whose parents gave poor ratings of their own or their child’s oral health were more likely to follow the less favourable trajectories.
In Chapter 7, findings from Dunedin study data on biomarkers of poor health showed that children who had high caries experience at age 5 years (5+ caries-affected teeth) had higher risk for some metabolic abnormalities including BMI≥30, high waist circumference and being in the highest quartile for serum leptin by age 45 years. Furthermore, those who as children had high caries experience had aged more rapidly by midlife than those who had been caries-free.
Finally, findings from the Dunedin and Christchurch studies presented in Chapter 8 showed age-5 dental caries not to be associated with mental health disorders by midlife in either cohort. However, in the Dunedin study, cross-sectional associations were observed whereby participants with high caries experience at age 45 years were more likely to have externalizing disorders, thought disorders and tobacco dependence than those who had lower DMFS or who were caries-free. Interestingly, continuity in poor oral health (represented by study participants in the three less favourable permanent dentition caries trajectories identified in Chapter 6) was associated with a higher risk of mental disorders.
This thesis showed that individuals who had experienced dental caries by the age of five years were more likely to have poorer oral health, self-reported general health, some metabolic abnormalities, and were ageing at a faster rate by midlife than those who had been caries-free. Having dental caries at age five years was not associated with mental disorders in midlife, however, continuity in poor oral health across the lifecourse was associated with higher risk for mental disorders.
These longitudinal associations between childhood caries experience and poor health by midlife reinforce the importance of child oral health for later adult health and wellbeing. Taken collectively, these findings suggest that early childhood dental caries experience should be recognised as a useful marker for poor oral and general health in adult life.