A proposed 24 h lighting scheme for older adults

Abstract

Alzheimer's disease (AD) patients exhibit random patterns of rest and activity rather than the consolidated sleep/wake cycle found in normal, older people. Light treatment has been shown to improve rest and activity rhythms and sleep efficiency of AD patients, presumably through consolidation of their circadian rhythms. The circadian system is maximally sensitive to short-wavelength radiation. Two independent studies summarised here show that 30 lux at the cornea of blue light (λ _max = 470 nm) from light emitting diodes (LEDs) for 2 h in the early evening improved sleep efficiency of older adults, including those with AD compared to exposure to the same dose of red light. Because compliance to blue light treatment may be difficult for adults with AD, we conceived of a lighting scheme that might be more practical and as effective. White light dosages of different spectra and amounts for night and for day, based on a computational model for human circadian phototransduction, might be more readily accepted by seniors and by their caregivers. Implications for an improved visual environment and for better sleep efficiency of older adults are discussed.