Age and cohort rise in diabetes prevalence among older Australian women: Case ascertainment using survey and healthcare administrative data

Background: Due to the absence and or costliness of biological measures such as glycated haemoglobin, diabetes case ascertainment and prevalence studies are usually conducted using surveys or routine health service use databases. However, the use of each of these sources is associated with its limitations potentially impacting the quality of the case ascertainment and prevalence estimation. This study aimed at ascertaining diabetes cases and estimating prevalence among mid- and older-age women through simultaneous use of a longitudinal survey and multiple healthcare administrative data sources. Methods: Data were available for 12,432 and 13,714 women born in 1921–26 and 1946–51 from the Australian Longitudinal Study on Women’s Health (ALSWH). Diabetes was ascertained using the ALSWH survey, health service use, and cause of death data. Parsimonious multiple logistic regression analyses tested associations between sociodemographic and health variables and the presence of diabetes. Results: In both cohorts, two or more of the sources captured more than 80% of the women with diabetes. The point prevalence of diabetes increased from 8.4% when the mean age of the women were aged 73, to 22.0% of surviving women at age 90 in the 1921–26 cohort; and from 2.6% at age 48 to 15.8% at age 68 in the 1946–51 cohort. In the 1921–26 cohort, women who were obese (OR: 3.56; 95 CI: 3.04–4.17) and women who were sedentary (OR: 1.18; 95 CI: 1.09–1.40) were more likely to have diabetes compared to those who had a normal weight and engaged in a moderate level of physical activity. In the 1946–51 cohort, the odds of diabetes increased three times (OR: 2.99; 95 CI: 2.54–3.52) for overweight women and nine times (OR: 8.78; 95 CI: 7.46–10.33) for obese women compared to those who had normal weight. Conclusions: The simultaneous use of multiple data sources improved the validity of diabetes case ascertainment. Application of this methodology in future studies may have important benefits including estimation of disease burden, health service needs, and resource allocation with improved precision. Diabetes prevalence increased with age, was much higher in the 1946–51 cohort than in 1921–26 at similar ages, and was significantly associated with physical inactivity and obesity. Interventions to promote physical activity and a healthy weight are needed to prevent the rising prevalence of diabetes across successive generations.