Machine learning identifies clusters of multimorbidity among decedents with inflammatory bowel disease
Postill G, Harish V, Itanyi IU, Tang F, Buajitti E, Kuenzig ME, Rosella LC, Benchimol EI. Commun Med (Lond). 2025; 5(1):476.
Purpose — To determine whether autoimmune hypothyroidism (AIHT) influences breast cancer (BRCA) incidence or all-cause survival.
Methods — Administrative data were used to identify elderly women living in Ontario, Canada with and without AIHT based on prescriptions for levothyroxine (LT4) (N = 178,186). Women were followed from April 1, 1994–March 31, 2003 for BRCA outcomes.
Results — The incidence of BRCA was similar in LT4 users and a propensity-matched cohort of non-users (adjusted HR = 0.99; 95% CI: 0.92–1.07). All-cause mortality was significantly lower in LT4 users compared to non-users (HR 0.95; 95% CI: 0.93–0.97, P < 0.001), as was all-cause mortality following BRCA diagnosis (HR 0.87; 95% CI: 0.77–0.98, P = 0.02).
Conclusions — LT4 use, as a surrogate for AIHT, is not a risk factor for BRCA in elderly women. The small survival advantage noted among LT4 users who developed BRCA likely represents a ‘healthy user’ effect. Further study is needed to investigate whether autoimmunity in general is related to BRCA development or related outcomes.
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Citation
Sandhu MK, Brezden-Masley C, Lipscombe LL, Zagorski B, Booth GL. Breast Cancer Res Treat. 2009; 115(3):635-41. Epub 2008 Jul 5.