Association between type 2 diabetes mellitus and breast cancer risk: results from a population-based cohort study in Chinese women
Menée à partir de données portant sur 72 295 Chinoises (âge : 40-70 ans ; durée médiane de suivi : 19,08 ans), cette étude analyse l'association entre un diabète de type 2, sa durée et le risque de cancer du sein (1 759 cas)
Background: Although numerous epidemiological studies have reported significant associations between type 2 diabetes mellitus (T2DM) and breast cancer incidence, considerable heterogeneity exists across studies. Moreover, the breast cancer risk in relation to T2DM duration remains unclear. This study aimed to investigate the associations between T2DM, T2DM duration, and breast cancer risk in Chinese women.
Methods: A total of 72,295 women aged 40–70 years from the Shanghai Women’s Health Study were included. T2DM was defined as diagnosis after age 30, and categorized as prevalent at enrollment or incident during follow-up. Incident T2DM was treated as a time-dependent exposure in Cox proportional hazards regression models. The risk trajectory of breast cancer following T2DM diagnosis was characterized using categorical modelling analysis.
Results: Over a median follow-up of 19.08 years, 1,759 incident cases of breast cancer were identified. Compared to individuals without diabetes, overall T2DM was associated with an increased risk of breast cancer (HR = 1.22, 95%CI: 1.05–1.43). This association was significant in women diagnosed with incident T2DM during follow-up (HR = 1.28, 95% CI: 1.05–1.55) but not in those with prevalent T2DM at enrollment (HR = 1.15, 95% CI: 0.90–1.46). A clear trajectory of trend was observed, with the highest risk occurring within the first 5 years after T2DM diagnosis (HR = 4.22, 95% CI: 3.27–5.44).
Conclusions: T2DM was associated with an elevated breast cancer risk in Chinese women, which peaked at approximately 5 years post-diagnosis. Future studies should collect detailed information on treatment and lifestyle changes in study populations, to enable more in-depth analysis.
BMC Public Health , article en libre accès, 2026