A cost effective method is a wrist actigraph, to note activity.

Agree that actigraphy may be your best bet.

A combination of questionnaire and actigraphy may work well. Sleep diaries also help to annotate actigraph recordings.

Thank you for all the answers, I really appreciate the help.

I have a question about the use of the PSQI (and all the others questionnaires as well), can it be used in daytime sleepers? Since we are going to assess subjects that work at night, we don't know if there is a specific questionnaire for different sleep behaviours.

Yes PSQI can be used for day time sleepers also because it does not use am or pm in calculation of the score.

But take care that PSQI talks about last month readings so it can be repeated only after a month if you have a repeated intervention study. Other then that you can also use PIRS scale .

I agree some of the people who have responded already; actigraphy would be the most feasible. If you had lots of money you might like to add in melatonin levels. Good luck.

I think PSQI is a good option if you want to know about sleep quality in the last month. However if you want to measure sleep quality in a shorter time frame, you will need a different instrument. Actigraphy will give you quantitative data about sleep, which is only a part of sleep quality. You could combine actigraphy with sleep diaries. The most recent format for sleep diary (recently published in SLEEP) contains data about sleep quality. I hope this helps, good luck!

By Bio-marker I assume you want an objective measure and not a subjective measure. Questionnaires like the PSQI, Berlin Sleep questionnaire, etc. would not be considered an objective tool nor as a 'bio-marker'. Actigraphy measures movement and indicates quiet time versus movement time with 'estimates' of quiet time as 'sleep', however it does not give an objective indication of sleep quality. You may want to consider cardiopulmonary coupling measures of sleep to objectively assess sleep quality in your population. (http://www.ncbi.nlm.nih.gov/pubmed/22833347)

I have had another thought. You could try using the Richards Campbell Sleep Questionnaire (RCSQ) (Measurement of Sleep in Critically Ill Patients, Richards et al. 2000) in combination with actigraphy. The RCSQ comprises five visual analogue scales. It hasn't yet been validated with PSG in healthy individuals but the r for SEI and total RCSQ score was pretty good for patients in coronary care. It is very quick and easy to use.

Since you're asking for a biomarker and not a questionnaire/subjective measure (the majority of the answers), I'd recommend the arousal index taken from visually scored EEG (correlates modestly with next-day EDS). Also slow wave activity during NREM sleep is a good marker of the dissipation of sleep homeostatic drive. Derk-Jan Dijk is an author to search for the latter.

Sleep quality is - almost by definition I would say - a subjective phenomenon. I wonder how one would objectively define ones sleep as being of good quality? Isn't it mainly the level at which you are able to function the next day as well as your sleepiness levels the next day that would define the quality of ones sleep? I would be careful with EEG recordings. Some people never ever have any slow wave sleep, because their skull is to thick, hence the amplitude of the slow waves is too low to be defined as slow wave sleep. If people are alert and functioning well on a given day, it is safe to assume a sleep of decent quality, irrespective of what the EEG recording may want to make you believe.

Sleep quality is mostly subjective category.

I would highly recommend to use the Karolinska Sleep Diary to determine sleep quality. See the attached paper.

I would suggest to see sleep quality as consisting of serveral components not necessarily related to each other (e.g.):

Subjective Sleep Quality:

Several others have already metioned subjective sleep quality: How do we experience our sleep? PSQ is a good long term indicator for subjective sleep quality, our institute (V.Grote, www.humanresearch.at) has developed a short term questionaire that nicely reflects how we subjectively experience the recreating effect of sleep.

Cortical Sleep Quality:

EEG rating after Rechtschaffen and Kales indicate, how well our Cortex followed the sleep stages 1-4 and REM, how good our sleep architecture looks like.

Autonomic Sleep Quality:

Heart Rate Variability (HRV) gives a good overview about the autonomic switches between Sympathetic (REM) and Parasympathetic (Non-REM) activity during sleep. Not only sleep architecture, also the depth and structure of autonomic relaxation can be measured using HRV analysis.

As mentioned, the information gained from the three parameters may be divergent. This does not mean, one is wrong, it simply confirms, that differents aspects of sleep are met. It demonstrates, that sleep, although not visible to the outside observer, is a tremendously complex and active process, essential for our regeneration and recreation and therefore essential for our health!

I think sleep quality is a quite complex measure, defined differently by different researchers. Daniel Buysse, aone of the originators of PSQI, emphasizes both quantitative and qualitative aspects, such as duration of sleep, sleep onset latency and perceived restfullness of sleep (all part of PSQI). However, emphasizing quantitative measures I'd say these might be more correctly meassured by using actigraphs. Possibly you should combine sleep questionnaires with objective instruments.

actography, PSQI and the richard campbell sleep questionaire are all good tools. recently there was an Iphone app (made by some team at stanford that measures sleep too. I have tested out on my self and it seems to do what is says it does, may be worth exploring. its called "sleep time" by Azumio... though there is a youtube video -- search "azumio sleep time" with Dr. Kendall Ho and a link to UBC school of med... let me see... ehealth.med.ubc.ca/resources/mobileapps

and you may have already consulted this but there is a book I came across all about tools...

TITLE "STOP, THAT and One Hundred Other Sleep Scales"

Editors:Azmeh Shahid, Kate Wilkinson, Shai Marcu, Colin M Shapiro

… show all 4 hide

ISBN: 978-1-4419-9892-7 (Print) 978-1-4419-9893-4 (Online)

Actigraph is able to give some objective measures. Are you thinking about biological markers as blood tests?

@Vini Bains: A phone-based app would be great indeed, but we might get into some language issues, as I would need a portuguese version of it. And about the book, yes, I read it while looking for a subjective measure of sleep. Thank you for the answer

@ Imran Khawaja: yes, we were thinking of actigraph or blood test, like melatonin or inflammatory markers, although the literature doesn't cite reliable blood markers (as all biomarkers are). We are going to collect blood for other tests but the goal of our research is looking more into the sleep quality than a complete reading of oneself sleep pattern. Thank you for your answer.

Perhaps the content of the following link is useful to you:

http://www.medicina.uanl.mx/educacioncontinua/wp-content/uploads/2015/05/MEDICINA_UNIVERSITARIA_56.pdf#page=32