Why harmonizing cohorts in sleep is a good idea and the labor of doing so?

Sleep researchers have worked tirelessly over the decades developing and validating questionnaires for the measurement of impaired sleep. Many of these are described in the book published in 2012 called STOP, THAT, and 100 Other Sleep Scales [1]. In addition, questions have been developed and administered to answer specific research questions that differ from these standard questionnaires and collectively the variety of items assessing aspects of sleep-related issues are vast. Cost, convenience, and consideration of participant impact necessitate the use of self-reported items in large-scale epidemiological studies. However, despite their clinical utility, it is arguable that this plethora of questionnaires for the assessment of various dimensions of sleep including quality, sleepiness, chronotype, and specific sleep disorders may also, to some degree, have hindered the advance of sleep epidemiology.