Table 1 Questionnaire and video comparisons

Sleep latency: How long do you think you took to fall asleep?

Time from first time recumbent until first completed three minutes period of immobility.

Sleep duration: How many hours of actual sleep do you think you got?

Time between first time asleep (as estimated by above criteria) and last time recumbent, minus time spent out of bed.

If you woke up, how many times did you go to the toilet?

Number of times observed getting out of bed.

What position did you fall asleep in last night?

First position with greater than three minutes immobility.

What position did you wake up in?

Last position with greater than three minutes immobility.

Did you change sleep position during the night?

 0: Not at all

 1: Possibly once

 2: Possibly twice

 3: More than twice but not lots

 4: Lots of times.

Number of positions greater than three minutes.

 0: No changes

 1: One change

 2: Two changes

 3: Between three and eight changes^a

 4: Nine or more changes^a.

Did your legs twitch or jerk often while you slept last night?

 Yes, No, Don’t know

Presence or absence of sustained leg movements not associated with position changes.