I can only speak for myself, but generally the best part of the weekend is getting to sleep through it. During the work week my days tend to begin with an ear-shattering alarm punting me out of dreamland and into the morning rush hour, so the opportunity afforded by weekends to hit snooze as much as I feel like it (or better yet, not even set an alarm at all) are a cause for somnambulistic celebration.
The celebration might have been a bit premature however, because it turns out that every time you hit snooze, you are killing yourself, softly.
In a bummer of a study published last week in The Journal of Clinical Endocrinology and Metabolism, a team of researchers led by the University of Pittsburgh's Patricia Wong found that regular shifts in sleep-time can have a number of detrimental effects, including insulin resistance, higher body mass index (BMI), cardiovascular disease, and diabetes.
According to Wong and her colleagues, chronotypes—a person's preferred time to sleep during a 24-hour cycle—vary with the individual. The problem is that contemporary social obligations, particularly in occupations that involve shift work, often don't align with an individual's chronotype. This disjunction between a person's preferred sleep time and their actual sleep time resulting from social obligations is called Social Jet Lag (SJL), and as Wong and her colleagues found out, it might be killing us.
Over the course of seven days, Wong had 447 healthy men and women between the ages of 30 and 54 wear a wrist mounted accelerometer so that the research team could monitor the precise amount of sleep clocked by each individual. For each individual, the seven day period would include at least one night before a day off, so that the team could see how not having to work the next day affected an individual's sleep pattern.
Perhaps unsurprisingly, not a single one of the participants maintained their workday sleep schedule on their day off. The vast majority of the participants slept in (sleeping about 44 minutes later than on a workday on average), while a small minority woke up earlier. According to the researchers, many of those who slept in appeared to be compensating for sleep deficits earlier in their work week. Moreover, the researchers found that these metabolic problems were independent of other factors such as sleep disorders, smoking and socioeconomic status.
Although Wong's study is not the first to link irregular sleep patterns with poor health, it is the first to link sleeping shifts with metabolic problems (such as insulin resistance and increased BMI). The researchers speculate that this happens because a number of metabolic processes (such as fat accumulation in the tissues and food absorption in the gut) all have tissue specific circadian rhythms, biological clocks regulating internal processes that can get thrown out of sync by shifting sleep schedules. This also means that the more drastic the sleep shift between workdays and days off, the stronger the link to metabolic problems.
For the nocturnes like myself, who find themselves sleeping through entire days more often than they'd like to admit, Wong's revelations may come as tragic news—as much as I love sleeping in, I'm not sure I'm ready to sleep forever quite yet. On the plus side, now that sleeping in is a matter of life and death, it should make getting out of bed on Monday just a little bit easier.