Purpose: To determine whether the type of ophthalmic disease is predictive of sleep and wakefulness disturbances in young subjects with visual dysfunction.
Design: Prospective cohort study.
Participants and controls: Twenty-five subjects (ages 12-20) were recruited from the Missouri School for the Blind. Twelve controls with normal sight were recruited from a residential school.
Methods: Daily activity was monitored for 14 days using wrist actigraphy. Sleep and wakefulness measures were derived from actigraphy records by automated analysis. Visually impaired subjects were prospectively stratified by presence or absence of optic nerve disease.
Main outcome measures: Daytime napping and regularity of awakening time (wake-up time instability).
Results: Subjects with optic nerve disease napped in the daytime significantly more than other visually impaired children or normal sighted controls: 28.1+/-4.0 minutes per day (mean +/- standard error) versus 11.9+/-2.4 minutes per day in equally visually impaired subjects with intact optic nerve function versus 6.2+/-2.2 minutes per day in subjects with normal sight (P<0.0001). These subjects also showed significantly more variable awakening times than the other groups. Logistic regression revealed that subjects with optic nerve disease are 9.1 times more likely to demonstrate daily napping of more than 20 minutes per day than equally blind subjects without optic nerve disease (95% confidence interval [CI] = 1.4-58.7, P = 0.02). Blind subjects with optic nerve disease are 21.3 times more likely than children with normal sight to nap more than 20 minutes on average per day (95% CI = 1.2-378, P = 0.04).
Conclusions: Optic nerve disease is predictive of increased daytime napping in young visually impaired subjects, suggesting that the nature and presence of ophthalmic disease affect the probability of concomitant sleep timing disorders.