How loneliness mediates the association between migration status and health trajectories: Longitudinal evidence from Germany

• Loneliness explains mental health disparities between immigrants and non-immigrants. • The mediating effect of loneliness on mental health is only significant among women. • Loneliness contributes to mental health disparities among immigrants who migrate at older ages. • Women who migrated after age 18 are particularly vulnerable to loneliness and poor mental health. • This study introduces parallel process latent growth curve modelling in migrant health studies. Evidence shows that immigrants tend to have better health upon arrival, but they experience faster health deterioration than non-immigrants. However, rarely do we assess the role of loneliness in shaping health disparities by migration status. This study examines how loneliness mediates the relationship between migration status and health. Using nationally representative data from the 2012–2020 German Socio-Economic Panel, we apply a parallel process latent growth curve model with mediation analysis to examine the direct associations of migration status with mental and physical health trajectories, as well as the mediating role of loneliness, by gender and age at migration (6,609 non-immigrants; 634 immigrants). Among women loneliness mediates the relationship between migration status and mental health ( β = −0.013, 95% CI = −0.022 - −0.006, p < 0.01). Immigrants are more likely to experience loneliness, which is associated with poorer mental health. Analyses that account for gender and age at migration differences reveal that loneliness mediates the relationship only among women who moved to Germany after age 18 ( β = −0.015, 95% CI = −0.024 - −0.008, p < 0.001). Loneliness contributes to mental health disparities between immigrant and non-immigrant women. Immigrant women who migrated after age 18 are particularly vulnerable. We do not observe the same mechanism among men, nor for physical health. Given that the mechanisms vary by age at migration and gender, future studies should tailor their analyses to specific population subgroups to better understand the drivers of migration-related health disparities.