Assessing sleep health in a European population: Results of the Catalan Health Survey 2015

Objective To describe the overall sleep health of the Catalan population using data from the 2015 Catalan Health Survey and to compare the performance of two sleep health indicators: sleep duration and a 5-dimension sleep scale (SATED). Methods Multistage probability sampling representative of the non-institutionalized population aged 15 or more years, stratified by age, gender and municipality size, was used, excluding nightshift-workers. A total of 4385 surveys were included in the analyses. Associations between sleep health and the number of reported chronic diseases were assessed using non-parametric smoothed splines. Differences in the predictive ability of age-adjusted logistic regression models of self-rated health status were assessed. Multinomial logistic regression models were used to assess SATED determinants. Results Overall mean (SD) sleep duration was 7.18 (1.16) hours; and SATED score 7.91 (2.17) (range 0–10), lower (worse) scores were associated with increasing age and female sex. Alertness and efficiency were the most frequently impaired dimensions across age groups. SATED performed better than sleep duration when assessing self-rated health status (area under the curve = 0.856 vs. 0.798; p-value <0.001), and had a linear relationship with the number of reported chronic diseases, while the sleep duration relationship was u-shaped. Conclusions Sleep health in Catalonia is associated with age and gender. SATED has some advantaged compared to sleep duration assessment, as it relates linearly to health indicators, has a stronger association with self-rated health status, and provides a more comprehensive assessment of sleep health. Therefore, the inclusion of multi-dimensional sleep health assessment tools in national surveys should be considered.

guarantees that, after the application of weights, the surveys in a given wave are representative of the Catalan population with a ±2% error margin [1].
The Catalan Institute of Statistics (Idescat) elaborates the list of titular and substitute sample units with all the logistic data need for interviewers to go to their dwellings to administer the surveys. To begin with, the list includes 5 substitutes per titular sample unit, but up to 5 additional substitutes can be provided if needed. All titular sample units receive an informative letter two week before the interview. At the time of the interview, professional interviewers go to the dwelling of each sample unit with the support of a computer. In case of impossibility to interview the selected subject after a given number of attempts, interviewers proceeded to the dwelling of the 1st substitute sample unit, personally handing the informative letter at the time of the interview. This procedure is repeated until a 100% response rate is achieved.
All ESCA interviews are delivered by professional interviewers with adequate formation, following an Interviewer's Protocol including detailed information on how the interviewer must present himself/herself; the attitude towards the interviewed person; how to contact the selected subjects; the procedure to follow in case of substitutions; the registration of incidents; and finally, how to ask the questions of each questionnaire included in the ESCA survey. The

SATED scale
The SATED -Satisfaction, Alertness, Timing, Efficiency and Duration-scale is a tool for the measurement of sleep health proposed by Buysse in 2014 [2]. SATED is the result of a comprehensive review of the literature on potential sleep health dimensions and their association with specific health outcomes in an attempt to create a tool capable of quantifying sleep health. During the development of the SATED tool, dimensions were considered as appropriate indicators of sleep health if they met the following criteria: (i) each dimension was associated with health outcomes, albeit with somewhat different outcomes for each dimension; (ii) they could each be expressed in positive terms; (iii) dimensions should be measurable across self-report, behavioral, and physiological levels of analysis; and (iv) each dimension had good face validity or ecological validity. The five dimensions of sleep that resulted the most relevant were: sleep duration (the total amount of sleep obtained per 24 hours); sleep continuity (the ease of falling asleep and returning to sleep); timing (the placement of sleep within the 24-hour day); alertness/sleepiness (the ability to maintain attentive wakefulness); and, satisfaction/quality (the subjective assessment of having "good" or "poor" sleep). In order to develop the shortest questionnaire targeting the five identified dimensions, five questions were developed using existing literature to identify the thresholds that discriminated the most the associations between the proposed sleep dimensions and health risks. The proposed questions were: sleep Satisfaction ("Are you satisfied with your sleep?"); Alertness during waking hours ("Do you stay awake all day without dozing?"); Timing of sleep ("Are you asleep, or trying to sleep, between 2:00 a.m. and 4:00 a.m.?"); sleep Efficiency ("Do you spend less than 30 minutes awake at night? This includes the time it takes to fall asleep and awakenings from sleep"); and sleep Duration ("Do you sleep between 6 and 8 hours per day?"). It should be noted that while sleep satisfaction is a purely subjective question, each of the other questions are tied to measurable sleep/wake behaviors. Respondents indicate the frequency with which they experience or engage in each dimension, with answers ranging from 0 to 2 points (0 = "never" or "very rarely"; 1 = "sometimes"; 2 = "often" or "always"). Items on the SATED scale can be totaled to produce a single summary score, ranging from 0 (poor sleep health) to 10 (good sleep health). This is consistent with evidence indicating that sleep symptoms or problems have additive effects on health outcomes [3,4].
Several limitations regarding the SATED scale must be acknowledged. First, the SATED scale has not yet been formally psychometrically validated. Although it was developed with an a priori conceptual model based upon previous empirical observations, the unique contribution of the selected domains has yet to be demonstrated. Similarly, the weight of each of the domains to the overall sleep health may not be proportional. In this sense, an ongoing validation project for SATED will provide the final sleep dimensions, questions, thresholds and weights if needed. Therefore, the preliminary version of SATED used in the current analysis may vary from the tobe-published validated SATED questionnaire. In the meanwhile, the only sources supporting the value of SATED are scientific initiatives using the same sleep health dimensions. For instance, a 2017 study from Furihata using the SATED dimensions concluded that both individual sleep dimensions and the aggregate measure of sleep health were associated with prevalent depression and the longitudinal development of clinically significant depression symptoms [5].
These results suggest that the specific dimensions, cut-off values and categorizations could reflect sleep health, and thus be useful. Moreover, it points out that individual dimensions occur in conjunction with the others and that a multivariate measurement could be more useful than individual measures for assessing health risks related to sleep health.