Of all the things to worry about in life, sleep may be the most pernicious. Most things you either can directly control (your booze intake, Twitter consumption, exercise regime) or you can’t (pollution, bees dying, malevolent artificial intelligence). But sleep sits right in the middle: even if you feel as if you are giving yourself enough, are you really? Is it the right sort? And then, of course, there’s always the worry that the worrying itself is a problem – by stressing yourself out about shut-eye, are you making things worse? First, take a deep breath. To start with the basics: if you are getting anywhere from seven to nine hours a night, you’re probably fine. “Some people can get away with as little as six hours a night, or might need as much as 10, but those are generally extreme cases,” says Jason Carter, dean of Baylor University’s Robbins College of Health and Human Sciences. “I would start to get concerned with consistently sleeping less than seven hours a night, and really concerned if it dropped to six or below.” As for the Donald Trumps and Margaret Thatchers of the world, proudly claiming that they were torching the midnight oil to fit all their responsibilities in, it’s not good news: “Based on multiple empirical studies, even those that get four hours of sleep are likely causing cardiovascular and metabolic damage to the body,” says Carter. “That may take years to manifest, even if they appear to be high-functioning on a day-to-day basis.” But when does this start to become a problem? After all, plenty of people have the odd work sprint – or a baby – and go for days, or sometimes months, without getting their regular hours in. “A random day once in a while isn’t anything to worry about,” says Dr Marie-Pierre St-Onge, director of Columbia University’s Center of Excellence for Sleep and Circadian Research. “That’s what we would describe as transient insomnia. Chronic insomnia occurs when you spend three months or more without regular sleep, and that is when I would start to be concerned. “One useful definition of overall sleep health is the RU-Sated framework, which assesses six key dimensions of sleep that have been consistently associated with health outcomes. These are regularity, satisfaction with sleep, alertness during waking hours, timing of sleep, sleep efficiency and sleep duration.” Of course, there is a difference between not even giving yourself a chance at a good night’s sleep – browsing Netflix until 2am, say – and having a restless night. “If you are waking up a lot in the night, this will impact the quantity and quality of your sleep, which can lead to compromises in your immune system, reduction in gut health and many other detrimental side-effects,” says Christopher Barker, a personal trainer and sleep management adviser. “It may be an indicator of a sleep disorder or another underlying health condition – if you’re concerned about any of these issues, it’s worth talking to your doctor.” So what is your best bet for catching some quality Zs? Well, start during the day. “Try to expose yourself to sunlight during the day to keep your circadian rhythms on track,” says St-Onge. Physical activity can also help: “Sleep and exercise have a bidirectional relationship,” says Barker. “In a 2013 poll, participants who undertook vigorous physical activity tended to fall asleep faster, woke up less during the night and woke up feeling refreshed, compared with non-exercisers.” When it’s time for bed, make sure you turn in at a reasonably consistent hour, and keep your sleep hygiene in shape. “You should try to keep your weekend routine within one to two hours of your weekday one, and keep them highly consistent,” says Carter. “I’d also suggest keeping your bedroom free of electronics, and keep it cool and dark. I often work with athletes, and one of the first things I ask them to do is activate their devices’ night mode, which cuts down on the emission of blue light that can impede sleep. Ideally, stay off all of your devices for an hour before bed.” Oh, and taking a deep breath (well, a number of them) really can work: there is evidence that it activates your parasympathetic nervous system and calms you down, making it the perfect way to wind down before bed.