RT Journal Article SR Electronic T1 Comorbidity patterns, family history and breast cancer risk: a latent class analysis JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 867 OP 872 DO 10.1136/jech-2022-219279 VO 76 IS 10 A1 Dalmartello, Michela A1 Vermunt, Jeroen A1 Parazzini, Fabio A1 Serraino, Diego A1 Giacosa, Attilio A1 Crispo, Anna A1 Negri, Eva A1 Levi, Fabio A1 Pelucchi, Claudio A1 La Vecchia, Carlo YR 2022 UL http://jech.bmj.com/content/76/10/867.abstract AB Background Limited evidence exists on how the presence of multiple conditions affects breast cancer (BC) risk.Methods We used data from a network hospital-based case–control study conducted in Italy and Switzerland, including 3034 BC cases and 3392 controls. Comorbidity patterns were identified using latent class analysis on a set of specific health conditions/diseases. A multiple logistic regression model was used to derive ORs and the corresponding 95% CIs for BC according to the patterns, adjusting for several covariates. A second model was fitted including an additional effect of FH on the comorbidity patterns.Results With respect to the ‘healthy’ pattern, the ‘metabolic disorders’ one reported an OR of 1.23 (95% CI 1.02 to 1.49) and the ‘breast diseases’ an OR of 1.86 (95% CI 1.23 to 2.83). The remaining two patterns reported an inverse association with BC, with ORs of 0.77, significant only for the ‘hysterectomy, uterine fibroids and bilateral ovariectomy’. In the second model, FH was associated with an increased risk of the ‘breast diseases’ pattern (OR=4.09, 95% CI 2.48 to 6.74). Non-significant increased risk of the other patterns according to FH emerged.Conclusion We identified mutually exclusive patterns of comorbidity, confirming the unfavourable role of those related to metabolic and breast disorders on the risk of BC, and the protective effect of those related to common surgical procedures. FH reported an incremented risk of all the comorbidity patterns.Impact Identifying clusters of comorbidity in patients with BC may help understand their effects and enable clinicians and policymakers to better organise patient and healthcare management.Data are available upon reasonable request.