Considering sleep apnoea, where sleep duration is not necessarily compromised, and many negative health outcomes, including all-cause mortality, have been reported, it is to be expected that other aspects of sleep are also important.
Numerous epidemiological studies have demonstrated associations between self-reported sleep duration and health outcomes, including cardiovascular disease, diabetes, weight gain and all-cause mortality (e.g. Cappuccio et al., 2010, 2011; Castro-Costa et al., 2011; Gallicchio and Kalesan, 2009; Lyytikainen et al., 2011; Magee et al., 2012). Although in some of these studies aspects of sleep quality were considered (Cappuccio et al., 2010; Lemola et al., 2011), and sometimes even statistically controlled for (Mesas et al., 2011), in general the emphasis has been on self-reported sleep duration as assessed by a single question. There is little doubt that sleep duration is an important sleep parameter, but in the context of sleep and health it is to be expected that other aspects of sleep are also important. This is illustrated clearly by considering sleep apnoea, where sleep duration is not necessarily compromised, and many negative health outcomes, including all-cause mortality, have been reported, including community-based studies (Marshall et al., 2008), although some paradoxical contributions of apnoea to survival have also been reported (Lavie and Lavie, 2009).