The sleep disorders (variable name prefix SLQ) data set has questions on
sleep habits and disorders. In 2017-2018, the sleep time and awake time
questions in the SLQ were adapted from the Munich ChronoType Questionnaire
(Roenneberg et al., 2003) This included the addition of two questions on usual
sleep and wake times on weekend or non-workdays.
All participants aged 16 and older were eligible.
Interview Setting and Mode
These questions were asked in the home, by trained interviewers, using the
Computer-Assisted Personal Interview (CAPI) system.
Quality Assurance & Quality
The CAPI system is programmed with limited built-in consistency checks to
reduce data entry errors. Additional edits were conducted post-data collection
as described in "Data Processing and Editing."
Data Processing and Editing
Edits were made to ensure completeness, consistency, and analytic usefulness
of the data. Approximately 3% of audio recordings of interviews were reviewed to
validate unusual times reported for SLQ300, SLQ310, SLQ320, and SLQ330. Based on
review, the most common interview entry errors were the incorrect assignment of
AM or PM for the reported day or night periods (e.g., 12 PM was entered for 12
AM when midnight was reported as usual time the participant falls asleep), and
the transposition of digits when minutes were recorded (e.g., ‘03’ for ‘30’).
Comments from interviewers also were considered. Edits were made to
approximately 45% of the reviewed records.
Summary variables for usual number of hours of sleep on weekdays (SLD012) and
weekends (SLD013) were derived from reported times. Hours were rounded to the
nearest half hour. For SLD012 and SLD013, hours of ‘less than 3’ and ‘more than
14’ were grouped and recoded with these value labels. For participants with
either of these low or high hours, times in SLQ300, SLQ310, SLQ320, SLQ330 were
set to missing to minimize disclosure risks.
Please refer to the NHANES Analytic Guidelines and the online NHANES Tutorial for further details on the use of sample
weights and other analytic issues.
SLQ300 (usual sleep time on weekdays or workdays): The wording for this
question was modified slightly from the 2015-16 cycle. Instead of the time the
participant usually “goes to sleep”, the current question asked the time the
participant usually “falls” asleep.
SLQ300, SLQ310, SLQ320, SLQ330 were formatted as character variables for time
in hours and minutes. Times between 00:00 (midnight) and 11:59 in the morning
indicate AM. Times between 12:00 (noon) and 11:59 at night indicate PM.
SLD012 (hours of sleep weekdays)/workdays) and SLD013 (hours of sleep
weekends/non- workdays) are derived variables, calculated from reported usual
sleep time (SLQ300 and SLQ320) and wake time (SLQ310 and SLQ330) during main
sleeping period (night or day). Respondents reporting that they woke up
periodically or that they slept for very short periods of times at night or
during the day were asked to report the sleep and wake time of their main
sleeping period. Therefore, the derived variables for hours of sleep, SLD012 and
SLD013, may not represent the total hours of sleep during a 24-hour period,
including naps or other periods of sleep. If sleep and wake times were not
reported, then derived summary variables were not calculated.