Unveiling the Relationship between Mental and Physical Health Trajectories Among Older Adult Cancer Survivors: The Moderating Role of Loneliness

Background: A cancer diagnosis and its treatment often have significant impact on an individual’s biopsychosocial outcomes, with both immediate and long-term negative consequences well-documented in the literature. As survivors of cancer are living longer, the long-term trajectory of mental and physical health among older adults who are survivors of cancer has received limited attention, with even fewer studies untangling the potential mechanism between the trajectories. One theoretically motivated moderator in this relationship is loneliness.

Methods: Using the nationally representative Health and Retirement Study (HRS), we characterized long-term trajectories of mental and physical health outcomes for U.S. adults over age 50 and explored their relationships. HRS is a longitudinal, population-based national sample that (re-)interviews ~20,000 participants every two years since 1992 on health, employment, income, mental health, and other outcomes. The primary mental health outcome used was depression, as measured by the Center for Epidemiological Studies – Depression Scale (CES-D, higher score means worse depression); and the primary physical health outcome was measured by Self-Rated Health (SRH, lower score means worse depression), a well-established single-indicator of an individual’s global/general health status.

Analysis: In addition to descriptive statistics, latent growth curve models were used to characterize the long-term trajectories of mental health (depression) and physical health (SRH) across the latest 4 waves of HRS data. The relationship between mental health trend (latent intercept and slope) and physical health trend (latent intercept and slope) was evaluated using the structural equation model (SEM) framework, and moderator analysis was conducted using multiple group SEM. Models were design-adjusted for complex survey design features and, therefore, path coefficients are nationally representative.

Results: 3,919 respondents (43% female; mean-age at HRS entry=56, 20-90; 17.3% Black/African American, 72.4% White/Caucasian, 10.3% Other race) reported having a cancer diagnosis. Latent growth curve models revealed a statistically significant worsening trend of depression (b=0.016, p=0.007) and self-rated health (b=-0.065, p<0.0001), both were modeled as latent slope variables. In addition, higher baseline depression significantly predicted cancer survivors’ worse baseline SRH, b=-0.602, p<0.0001, and the worsening trend of cancer survivors’ depression significantly and negatively predicted their trend of SRH, b=-0.477, p<0.0001. Importantly, multiple group SEM revealed the significant moderating role of loneliness on the relationship between trajectories of depression and SRH, with such a relationship only existing among cancer survivors with low levels of loneliness (b=-0.463, p<0.0001) but not those with high levels of loneliness (b=-0.001, p=0.698).

Discussion: This study is among the first that evaluated the relationship between the long-term trajectories of mental and physical health in cancer survivors and the potential moderating role of loneliness in such a relationship. The findings of this study not only solidified the long-term physical health consequences of deteriorating mental health among survivors of cancer but also highlighted the critical importance of integrating loneliness into the understanding of such a relationship. When supporting cancer survivors’ long-term mental and physical health, oncology social workers are encouraged to critically evaluate their loneliness – an increasingly important risk factor, especially among the older population – for better care.