Disturbed sleep has a major impact on quality of life and is often a common symptom of many other chronic conditions, such as chronic pain and mood disorders.
The Sleep Problems Index I (SPI-I), a global summary of sleep quality, is calculated from responses to all 6 items included on the 6-item version of the MOS Sleep Scale-R, while the SPI-II is calculated from responses to 9 of the items on the 12-item version of the MOS Sleep Scale-R. Both the 12-item and 6-item versions are available with a standard four-week recall period, or with an acute one-week recall period.
