I woke up yesterday and immediately knew something was different. A familiar but unusual feeling came over me. Like kindling a fire, at first it was delicate and tentative, but as I began my morning routine, the feeling grew until it was a roar. That feeling was energy. I was switched on. Alive. Motivated. Before I’d even had my breakfast, three great ideas had popped into my head.  

Energy is not something I’ve had in abundance lately. In fact, some days I’ve felt wiped, especially in the early evenings when I’ve been turning into a zombie. So what was different on this morning? Where had the energy materialised from? The answer boils down to just one word – sleep. I’m the mother of a newborn baby, and for the first time in nine weeks, I had spent nine blissful hours in the Land of Nod. My son slept from 9pm until 4:30am, then after a feed and a cuddle, he went back to sleep until 9:30am.  

Regular readers of this blog will know that I’m a huge advocate of the importance of sleep. As I’ve written about previously, despite what some of the world’s most influential people would have you believe (ahem, Donald Trump), most healthy, successful people actually get more sleep, not less. With recent research linking poor sleep to many chronic diseases and demonstrating that lack of sleep may have not only been one of the causes of my autoimmune disease, but that it also exacerbated my symptoms, I now make sleep one of my top priorities.  

I recently wrote about all this in a blog post dedicated to sleep deprived people and one of the readers of that post asked me what I knew about how much sleep we need. Nico wrote about his “magnificent girlfriend” who “definitely requires a few more hours asleep daily” than he does. He asked, “Have you any advice/knowledge on whether the recommended 7-9 hour nightly sleep is a normative necessity for all people? Can some individuals require more (9+ hours) or less (7- hours) than what is advised?”  

This is such a great query. After all, there is a whole lot more we could get done by staying awake for an extra two hours. So when I had the chance to interview one of the world’s leading sleep experts, I asked him that very question.  

German scientist Till Roenneberg from Ludwig-Maximilian University, is an expert in the field of chronobiology (the study of our biological rhythms) and draws on data collected from more than 55,000 people to study our sleep needs. It’s commonly thought that we should all be aiming for about eight hours sleep each night, though occasionally news stories carry headlines like “Why Seven Hours of Sleep Might be Better than Eight”. When I asked Ronneberg what we really know about how much sleep we should be getting, his response was surprising. “Nothing,” he said bluntly. So I asked him to elaborate. “I really mean it. We don’t really know how much. We know how much people on average get, but do we don’t know whether that is the right amount.”  

It seems the confusion comes down to the fact that we are all different – different genders, different ages, different daily activities. All these differences mean that we all need a different amount of sleep. That said, there are some evidence-based rough guidelines we can use. In 2009 a rare genetic mutation was discovered that allows some people to sleep less than 6.25 hours a night with no negative effect. Unfortunately, it’s thought that this super power is limited to less than one percent of the population. For the rest of us, depending on our age and gender, most of us need somewhere between seven to nine hours of sleep every night. Toddlers need around thirteen hours, including a daytime nap. Teenagers need around nine and a half hours, and women tend to need more sleep than men. The amount of sleep you need from day to day will also vary. Studying for exams, preparing for a major presentation at work, training for a marathon – these kinds of activities all demand more from you, and as a result, you’ll need more sleep.  

Fortunately there’s a very simple way to determine how much sleep you as an individual will generally need, which I’ve outlined at the end of this post. When I did this simple exercise for myself, the results were stunning. At the time I was getting about seven hours of shut eye on a good night, but I discovered that I’m a nine hour woman. Anything short of that leaves me depleted. Given that I’ve been getting five to seven hours of broken sleep since my nine-week-old son came into the world, it’s little wonder I’ve been feeling flat.  

I’m not alone in not getting enough sleep. The US National Health Interview Survey of more than 250,000 people found that almost 30 percent of men and women were sleeping less than six hours each night^⁠. According to the UK Mental Health Foundation, over 30 percent of the population suffers from insomnia. An Australian study found that kids around the world are being affected too and are losing on average 37 minutes each night of recommended sleep.  

Ronneberg explained that part of the problem is that we all have different biological rhythms that mean we like to sleep at different times. Some people are night owls, others are morning larks. This “social jet lag”, as Ronneberg calls it, may well be one of the reasons we’re suffering the health consequences of not getting enough sleep. For instance, when researchers experimentally disrupted people’s sleep cycle they found a significant deterioration in mood, which goes towards explaining why a high prevalence of anxiety, depression and other mood disorders is reported among shift workers who’s sleep rhythms are constantly being challenged. “If we could change society so that people can actually sleep in their sleep windows, we would not only know very more about how much sleep we actually need, we would all be very much healthier, because we would get the sleep at the right time and the right amount that we individually need,” said Roenneberg who advocates for a different way of living according to our individual sleep needs.  

Unfortunately at the moment I’m operating on the sleep schedule that nine-week-old Isaac determines and, alas, my nine hours of bliss seems to have been a one-off for now. There is good news though if you’re regularly doing shift work or, like me, facing some other unavoidable obstacle to getting enough sleep regularly. A study from the University of Pennsylvania found that one or two nights of good sleep was enough to help people rebound from five nights of sleeping too little. That said, it can take weeks, and sometimes longer, to recover from long term sleep deprivation. My fingers are crossed that little Izzy Harvey gets the hang of this whole day and night thing in near future.  

Find Out How Much Sleep You Need  

Schedule a week that you can dedicate to sleeping. Go to sleep when you’re tired and get up in the morning when you feel refreshed, without an alarm. Limit your caffeine and alcohol consumption as well as your exposure to blue light after sunset (more about that here). During the day, get out into the sunlight and exercise. After a week or so you should have paid off any accumulated sleep debt and you’ll start finding your natural rhythm. (Please note that if you do all this and you’re still experiencing trouble sleeping, it might be time to talk to a doctor or experts at a sleep clinic.)