Associations of ambient illumination with mood: Contribution of ophthalmic dysfunctions

Evidence suggests that ocular pathology could reduce light-stimulated neuronal signaling to the suprachiasmatic nuclei. This study investigated associations of ambient illumination with moods, while considering the contribution of ophthalmic dysfunctions. Seventy Black (59%) and White (41%) Americans participated in the study. Their average age was 68.27±5.97 years; 73% were women. Baseline data included: physical health, mood, and sociodemographics. Ophthalmic factors including visual acuity, visual field defects, intraocular pressure, vertical and horizontal cup-to-disk ratios, and nerve-fiber-layer thickness were assessed at SUNY Downstate's eye clinic. The following week, participants wore the Actiwatch-L at home to monitor ambient illumination and sleep. Cosine analyses were performed on the logarithm of measured illumination, yielding the mesor and acrophase of daily illumination exposure. Sleep was estimated with an automatic scoring algorithm. Of the sample, 25% reported visual impairment and 85% reported good to excellent health; 27% were visually impaired according to American criteria. Partial correlation analyses showed an inverse correlation of daily illumination levels to depressed mood [rp=−0.33, P<0.05], when age, sex, ethnicity, income, BMI, diabetes, hypertension, respiratory disease, and habitual sleep duration were controlled. With further control for ophthalmic factors, the magnitude and significance of the correlation diminished [rp=−0.26, NS]. Individuals receiving daily illumination later in the day reported more depressed moods [rp=0.36, P<0.01]; of note, this correlation was not significant after control for the covariates [rp=0.18, NS]. Regression analysis indicated that the ophthalmic factors explained 13% of the variance in depression. Our results show that both the level and timing of ambient illumination are associated with mood. Furthermore, they suggest that visual impairment has a mediating effect on the associations of ambient illumination with depression, supporting the notion that ocular pathology lessens the efficacy of daily illumination in promoting positive moods.