Background A substantial body of research has pointed to an association between socioeconomic position (SEP) and the prevalence of type 2 diabetes (T2D), whereby those in lower social classes are disproportionately affected by the disease. However few studies have examined the contribution of SEP trajectories across the life course to the development of T2D. We investigate the independent and synergistic effects of childhood and adult SEP, as well as the effect of social mobility, on T2D risk in later life.

Methods Cross-sectional data from The Irish Longitudinal Study of Ageing (TILDA) (n=4998), a nationally representative probability sample of adults aged 50 and older, were analysed. Prevalent diabetes was defined using subjective (self-reported doctors diagnosis) and objective data (medications usage and glycated haemoglobin testing). SEP was classified as a three level variable (low, intermediate, high) based on fathers occupation in childhood (origin SEP) and respondents primary occupation in adulthood (destination SEP). A 5-level social mobility variable was created from cross-classification of origin and destination SEP (‘Stable High’ ‘Stable Intermediate’, ‘Stable Low’ ‘Upwardly Mobile’ and ‘Downwardly Mobile’). Logistic regression was employed to assess the relationship between SEP variables and T2D. All analyses were adjusted for age and age², and stratified by sex.

Results Mean (SD) age of the sample was 63.0 (9.2)y and 46.4% were male. Prevalence of T2D was 9.5% (95%CI: 8.6%–10.6%). 53.4% of the sample were classified as ‘Low SEP’ in childhood which decreased to 33.7% in adulthood.Compared to high SEP, low SEP in both childhood (Odds Ratio (OR): 1.84, 95% CI: 1.00–3.37) and adulthood (OR: 1.78, 95% CI: 1.02–3.13) was independently associated with T2D in women. When classified according to social mobility, women classified as ‘Stable Low’ were at greatest risk of T2D (OR: 2.51, 95% CI: 1.24–5.06) compared to those classified as ‘Stable High’. No associations were noted between any SEP variables and T2D in men.

Conclusion This study confirms a strong association between low socioeconomic position and T2D in women which persists from childhood through to adulthood. These findings support the critical period hypothesis which suggests that social disadvantage experienced in early life may have long lasting health consequences – in this case an increased risk of T2D. As many risk factors for T2D result from poor health behaviours which are likely adopted in early life, interventions to reduce T2D and its causes at a population level should recognise high-risk groups at all stages of the life course.