Debates on how sex, gender, and sexual identity relate to intimate partner violence (IPV) are longstanding. Yet the role that measurement plays in how we understand the distribution of IPV has been understudied. We investigated whether people respond differently to IPV items by sex and sexual identity and the implications this has for understanding differences in IPV burdens. Our sample was 2,412 randomly selected residents of Toronto, Canada, from the Neighborhood Effects on Health and Well-being (NEHW) study. IPV was measured using short forms of the Physical and Nonphysical Partner Abuse Scales (20 items). We evaluated the psychometric properties of this measure by sex and sexual identity. We examined whether experiences of IPV differed by sex and sexual identity (accounting for age and neighborhood clustering) and the impacts of accounting for latent structure and measurement variance. We identified differential item functioning by sex for six items, mostly related to nonphysical IPV (e.g., partner jealousy). Males had higher probabilities of reporting five of the six items compared to females with the same latent IPV scores. Being female and identifying as lesbian, gay, or bisexual were positively associated with experiencing IPV. However, the association between female sex and IPV was underestimated when response bias was not accounted for and outcomes were dichotomized as "any IPV." Common practices of assuming measurement invariance and dichotomizing IPV can underestimate the association between sex or gender and IPV. Researchers should continue to attend to gender-based and intersectional differences in IPV but test for measurement invariance prior to comparing groups and analyze scale (as opposed to binary) measures to account for chronicity or intensity.
Keywords: Canada; gender; health equity; intimate partner violence; measurement; psychometrics; sex; sexual identity.