Clock-drawing potentially mediates the effect of depression on mortality: Replication in three cohorts

Objective: Previously studies have associated visuospatial tasks, particularly 'clock-drawing', with mortality. We sought to determine whether clock-drawing also mediates the association between depressive symptoms and mortality. Participants: Non-institutionalized Hispanic and non-Hispanic White elderly volunteers. Measurements: Survival curves were generated as a function of baseline depressive symptom ratings. Significant models were adjusted for CLOX performance. CLOX is divided into CLOX1, a measure of executive control, and CLOX2, a measure of visuospatial skills. Design: Retrospective analysis of three longitudinal cohorts. Results: CLOX2 and depressive symptoms were both associated with mortality in unadjusted models. CLOX2 predicted survival independently of CLOX1 in all three cohorts. CLOX2 also attenuated, and/or mediated the association between depressive symptoms and mortality. These results withstood adjustment for age and education in all three cohorts. Conclusion: Regardless of the sample examined, or the measure of depressive symptoms applied, the association between depressive symptoms and mortality appears to be at least partially mediated by visuospatial skills. This finding supports our hypothesis that right hemisphere structural brain disease, particularly that involving the insula, may mediate depression's effects on mortality.