From hypothesis to robust evidence in a nationwide multicenter case-control study on 1490 women: milk stasis and idiopathic granulomatous mastitis

Abstract

Idiopathic granulomatous mastitis (IGM) is rare globally and infrequent in some middle-east regions. Sex-hormonal factors have been mentioned as predisposing factors for IGM, recent large-sale studies indicate a 7.5-fold increased risk in women who have breastfed. This study investigates BF-related factors that contribute to IGM development. We conducted a multicenter case-control study and recorder BF-related events in 730 IGM patients and healthy 760 controls. The mean age of participants was 36.63 +/- 6.49 in the Case and 36.96 +/- 6.11 years in the Control Group (p = 0.31). IGM occurred more frequently in the contralateral breast in one-sided BF (p < 0.001), with discordance between the affected side and BF side in 68.3 of cases (p = 0.005). Multivariate analysis revealed significant associations between IGM and one-sided BF (OR = 4.21), post-weaning breast engorgement (OR = 3.06), lactational mastitis (OR = 1.93), and oral medication use for infants (OR = 2.59). The study achieved 100 statistical power for both primary and secondary objectives, with narrow confidence intervals indicating high precision. This study provides robust evidence supporting the milk stasis hypothesis, demonstrating that BF-related issues leading to milk stasis are strongly associated with IGM development. Preventive strategies to minimize milk stasis and encourage bilateral BF may help reduce IGM risk.