Development of a sleep disturbance index (SDI) for the assessment of noise-induced sleep disturbances

Abstract

This analysis was aimed at the development of a sleep disturbance index (SDI) which allows a reliable estimate of physiological sleep disturbances due to environmental influences such as noise. Seven variables, repeatedly reported to change during noise exposure, were derived from polysomnograms of a reference sample of 38 men and 28 women (19–34 yrs) as recorded under quiet conditions in the laboratory after at least one habituation night. The variables were then submitted to a principal component analysis. The scores of the first principal component that explained 35 % of the variance were used to calculate the SDI. Reliability was ascertained by application of the SDI to a quiet night for each of 82 persons of the same age range from two other laboratory studies where the index value did not differ from that of the reference sample. Validity was verified by significantly lower index values for quiet nights than for noisy nights of 50 persons (25 men, 25 women, 19–28 yrs) and for the first night in the laboratory of 62 persons (37 men, 25 women, 19–34 yrs). Moreover, the index value increased with increasing age of the 261 participants in two laboratory studies and a field study whose age varied between 18 and 68 years. The SDI may facilitate the interpretation of sleep disturbances caused by environmental influences and its application would improve the comparability of studies performed in this area.