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Another day, another reminder that a good or bad night's sleep doesn't exist in a vaccum: In a new study published in the journal Sleep, researchers used data from the UK Household Longitudinal Survey to analyze the link between sleep habits, health and well-being. Their analysis included 30,954 people over age 16 who'd participated in the UKHLS survey for both 2009-2011 and 2012-2014 (each survey covers a two-year period). A little over half of the participants were female and most of them (almost 90 percent) were white. Sleep data from the survey enabled researchers to look at changes in sleep duration, sleep quality and sleep-medication use over the span of four years and see how those changes corresponded to levels of mental and physical health and general well-being. 

A few trends emerged with respect to sleep: Between 2009 and 2014, participants were twice as likely to report getting less sleep rather than more. Participants were also more likely to report cutting back, rather than ramping up, their usage of sleep meds. And, while more than half of participants reported changes in sleep quality (good or bad), they were roughly as likely to report sleeping better and sleeping worse. 

The UKHLS includes two different assessments of health and well-being. The General Health Questionnaire is a self-assessment of psychiatric symptoms in healthy (meaning non-psychiatric) patients. And the 12-item Health Survey measures quality of life with respect to both mental and physical health. Researchers used both assessments to evaluate the impact of sleep changes. 

Unsurprisingly, they found that decreased sleep, decreased sleep quality and increased use of sleep meds were linked to worse health outcomes. On the flip side, participants' whose sleep changed for the better reported improved mental and physical health to match. But, while all three sleep-related measures were predictive of well-being, sleep quality appeared to make the biggest difference. Researchers offered two points of comparison: Increased sleep quality was associated with similar levels of well-being as exhibited by people (in other studies) who'd just completed two months of mindfulness therapy and who'd won the lottery two years earlier. 

While the results generally mirrored researchers' predictions, a few surprises emerged. For instance, increased sleep duration was associated with improvements in mental well-being but not physical well-being. Researchers surmised that the benefits of longer sleep might not manifest in different domains of health at the same rate.

Additonally, in contrast to what this study shows, some previous research has suggested that sleep quantity is more directly and significantly linked to longterm health outcomes (e.g., mortality rates) than sleep quality. But, rather than look for the one, true determinant of sleep, researchers said, we should treat sleep as a multidimensional experience requiring a multidimensional assessment. This idea has been echoed by experts many times over. The National Sleep Foundation, for instance, published a paper earlier this year identifying the four main components of sleep quality. As it turns out, you can't evaluate sleep quality without doing at least some quantifying.