Interdependent associations between perceived threat and Mediterranean diet adherence among prostate cancer survivors and their partners.

339 Background: Drawing on the Health Belief Model, greater perceived illness threat typically motivates healthier behaviors. In couples, these effects may be interdependent, with one partner’s perceived threat influencing both their own and their partner’s health behaviors. However, no study has tested this interdependent association among prostate cancer (PCa) survivors and partners. This study aimed to 1) examine the interdependent associations between perceived threat and adherence to the Mediterranean (Med) Diet among PCa survivors and partners, and 2) assess whether these associations were moderated by neighborhood socioeconomic deprivation, measured by the Area Deprivation Index (ADI). Methods: We analyzed the secondary data collected from the control arm of a clinical trial (N = 139 survivor–partner dyads) at baseline (T1), 4 (T2), 8 (T3), and 12 (T4) months. We measured perceived threat and Med diet adherence with reliable and valid self-report surveys. At each time point, we fitted structural equation models with Actor-Partner Interdependence Modeling (APIM) to estimate actor effects (one’s perceived threat → one’s own adherence) and partner effects (one’s perceived threat → partner’s adherence). All models adjusted for family income; missing data were imputed via Random Forest. We then added ADI as a dichotomous moderator (high vs. low deprivation) to test interaction effects. Results: Main Effects. Lower perceived threat was associated with higher Med diet adherence for both survivors and partners. Significant actor effects (one’s perceived threat → one’s own adherence) occurred for survivors at T2 (p = 0.013) and for partners at T1 (p = 0.008) and T2 (p < 0.001). A partner effect (one’s perceived threat → their partner’s adherence) emerged at T2: partners’ lower threat was related to survivors’ greater adherence (p = 0.037). Moderation by ADI. In high-deprivation neighborhoods, survivors’ actor (p < 0.001) and partner (p = 0.036) effects at T2 were amplified—i.e., among survivors, the perceived threat was more strongly associated with both their own and their partners’ Med diet adherence. Conversely, for partners in deprived areas, both actor effects at T2 (p = 0.006) and partner effects at T3 (p = 0.026) and T4 (p = 0.017) were attenuated. Conclusions: After PCa treatment, the more threatened or worried individuals felt, the less likely they were to follow the Med Diet, suggesting that emotional or cognitive responses to PCa experience might interfere with adherence to healthy eating. This relationship was moderated by high neighborhood deprivation and in opposite directions for survivors and partners. Targeted dietary interventions for PCa survivors and partners require a dual focus, addressing the psychological challenges tied to their perception of PCa and the practical barriers from limited neighborhood resources.