Changes in prevalence of diabetes over 15 years in a rural Australian population : the Crossroads studies

Aims: Secular trends in diabetes prevalence vary globally. We compared the prevalence of diabetes in two surveys 15 years apart in rural Australia. Method: Two cross-sectional household surveys and clinics (biomedical assessments including oral glucose tolerance tests (OGTTs)) in 2001–2003 (Crossroads) and 2016–2018 (Crossroads-II). Setting: Four rural Victorian towns. Participants: Residents of randomly selected households (Crossroads (n = 5258), Crossroads-II (n = 2649)) with nested clinic assessments for randomly selected participants (n = 1048 and 736 respectively). Response rate 61%. Main outcome measures: Self-reported diagnosed diabetes, screening history, and diabetes defined by OGTT. Results: The age standardised prevalence of diagnosed diabetes increased from 5.0(4.4–5.7)% to 7.7(6.7–8.6)%, with crude prevalence increasing overall (5.4 to 10.4% p < 0.001), in the smaller towns (5.4 to 11.1% p = 0.001) and, the regional centre (4.1 to 7.3% p < 0.001). Screening for diabetes over the previous two years increased (rural towns 49.8 to 63.8%; regional centre 44.9 to 63.6%; both p < 0.001). The proportion of undiagnosed diabetes was 23.2% in 2003 and 13.7% in 2018. The age and sex adjusted change in total diabetes was (1.15(0.84–1.59)). Central obesity (adjusted odd ratio 1.28(1.00–1.64)) but not overall obesity (adjusted odd ratio 1.17(0.95–1.46)) increased over time. Conclusions: Over 15 years, the crude prevalence of diagnosed diabetes increased while the age and sex adjusted total diabetes prevalence did not change significantly. The epidemic may be slowing in some settings.