Background: Depression is strongly associated with chronic disease; yet, the direction of this relationship is poorly understood. Allostatic load (AL) provides a framework for elucidating depression-disease pathways. We aimed to investigate bidirectional, longitudinal associations of baseline depressive symptoms or AL with 5-year AL or depressive symptoms, respectively.
Methods: Data were from baseline, 2-year, and 5-year visits of 620 adults (45-75 years) enrolled in the Boston Puerto Rican Health Study. The Center for Epidemiology Studies Depression (CES-D) scale (0-60) captured depressive symptoms, which were categorized at baseline as low (<8), subthreshold (8-15), or depression-likely (⩾16) symptoms. AL was calculated from 11 parameters of biological functioning, representing five physiological systems. Baseline AL scores were categorized by the number of dysregulated parameters: low (0-2), moderate (3-5), or high (⩾6) AL. Multivariable, multilevel random intercept and slope linear regression models were used to examine associations between 3-category baseline CES-D score and 5-year continuous AL score, and between baseline 3-category AL and 5-year continuous CES-D score.
Results: Baseline subthreshold depressive symptoms [(mean (95% CI)): 4.8 (4.5-5.2)], but not depression-likely symptoms [4.5 (4.2-4.9)], was significantly associated with higher 5-year AL scores, compared to low depressive symptoms [4.3 (3.9-4.7)]. Baseline high AL [19.4 (17.6-21.2)], but not low AL [18.5 (16.5-20.6)], was significantly associated with higher 5-year CES-D score, compared to baseline moderate AL [16.9 (15.3-18.5)].
Conclusions: Depressive symptoms and AL had a bi-directional relationship over time, indicating a nuanced pathway linking depression with chronic diseases among a minority population.
Keywords: Allostatic load; Hispanics; Latinos; Puerto Ricans; depression; depressive symptoms.