Measurement of Good Sleep Quality

Before we learn about the effects of poor quality sleep, we need to know what sleep quality is in the first place. To provide a simple definition, sleep quality means one's satisfaction with sleep experience. It takes into account various factors such as sleep initiation, sleep maintenance, quantity, and refreshment upon awakening. High-quality sleep is characterized by effortless transitions (between wakefulness and sleep as well as between sleep stages) and no interruption of sleep.

It is hard to define good quality sleep objectively, however. Even if polysomnographic recording for an individual shows a typical sleep progress chart, quality of sleep during that night can be defined as poor if the individual was not satisfied. Despite these complications, sleep assessments are used to determine the quality of a night or an extended period's sleep. These are three main aspects involved in sleep assessment: amount, quality, and architecture.

There are mainly two types of sleep assessment: those done post sleep and the survey-type. They have different time frames and each is thus specialized for distinct purposes. Post sleep assessments generally reflect more accurately on the night-to-night variations in sleep quality. On the other hand, survey-type questionnaires can provide insight on frequency or duration of specific problems. However, both assessment methods have their limitations–post sleep assessments do not provide long term insight into issues, and survey-type assessments cannot indicate the severity of the particular problem at the present time.

The Pittsburgh Sleep Quality Index (PSQI) is a sleep assessment that has the time frame intermediate between these two. It assesses the sleep quality of the previous month, and this time frame allows it to be free of the limitations in other assessment methods. The intermediate time frame of two to three weeks is, therefore, often used clinically to differentiate fleeting from persistent sleep wake disorders. Consequently, many researchers consider PSQI as reliable and validated and use it.

A PSQI consists of nineteen self-rated questions that assess sleep quality through estimates of sleep duration, latency, and frequency and severity of specific sleep-related problems. These questions are grouped into seven component scores that are each weighted equally on a 0-3 scale. Then, the seven component scores are summed for a global PSQI score (range of 0-21), with higher scores indicating worse sleep quality. The PSQI also includes five questions rated by a bed partner or roommate. They are used for clinical information only and are not taken into account for the scoring of the PSQI. The entire index requires 5-10 minutes for completion and 5 minutes to score.

Additionally, assessment of the three main aspects of sleep (amount, quantity, and architecture) can be done through a series of direct questions. These questions are divided into the respective sections. Questions for assessment on the amount of sleep include "What time do you usually feel tired?" and "When do you actually go to bed?" Questions for assessment on sleep architecture include "Do you have a set bedtime?" and "During the school week, do you sleep more or less than you do on weekends?" Questions for assessment on sleep quality include "Do you ever have problems falling asleep? How many times in the last month have you had such problems?" and "How often do you wake up in the middle of the night or early morning?"

Meanwhile, assessment of risk factors for disrupted or insufficient sleep involve assessing activities, habits, and environmental elements that can influence sleep. These factors include work, exercise habits, exposure to and use of electronic screens, and alcohol and caffeine usage. More information is available on the Sleep Quality webpage.