Intended for healthcare professionals

Career Focus

Sleep and work

BMJ 1999; 318 doi: (Published 30 January 1999) Cite this as: BMJ 1999;318:S2-7179

Should you let circadian rhythmicity choose your specialty? Carl Gray suggests you plan your day to suit your type

  1. Carl Gray, Consultant
  1. Department of Histopathology, Harrogate General Hospital

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    Most of doctors' problems start in bed, or, at least, in getting into and out of bed. Much of medicine consists of doing things we don't want to do when we don't want to do them. Unavoidably, most medical activity takes place on the surface of this difficult planet - it's the only one available so far. Its inescapable period of rotation is 23.93 hours, and the axial tilt of 23.45&#degree; with reference to the solar plane causes the annoying seasonal variation in daylight hours during the 365.25 sidereal days of the solar orbit. Unlike polar bears and bats, who work their rotas according to the actual light and dark cycle, most medics' activity is entrained by the 24 hour based timetables fixed by organisations and computers but not suited to human chronobiology.

    Unfortunately, humans have large interpersonal variations in effective diurnal cycles; few of us are accurately matched to the actual planetary rotation. Our internal clocks run to a virtual day that may differ widely from the 24 hour standard. Sleep often comes second to work, and, as Evelyn Waugh observed, you need more rest if you don't sleep.

    Scientific evidence

    In their seminal paper, environmental epidemiologists Gale and Martyn tested the validity of Benjamin Franklin's maxim “Early to bed and early to rise makes a man healthy, wealthy and wise.”(1) In 1229 men and women aged 65 and over the maxim was not supported: owls were slightly wealthier, but there was no significant difference in health or wisdom. Subjects who spent more than eight hours in bed each night had an increased risk of death for unknown reasons. The authors advised caution in extending their findings to younger people.

    Sleep deprivation and disorder are built into the tradition and folklore of medicine, but dysfunctional hours no longer need be so. Legal time limits and new shift systems should outlaw long hours of overwork, but unfavourable patterns of work will not necessarily be prevented.(2) Trainees should now have reasonable working hours, but the same workload may need to be compressed into the legal timetable. Consultants now have greater workloads than ever to cover, and many find that the working day is getting harder and longer.

    Hospital environments are often harsh, with time cues expunged - windowless rooms bleary with continuous lighting and the quiet hum of machines. Imposed ward routines often subject patients to early waking and bedtimes. Working counter to your biological pattern can cause a software crash that requires a reboot. Sleep deprivation inevitably leads to catastrophic “catch ups” - whole weekends lost to sleep. Being tired all the time and too tired to care is a tiresome waste of time. Relationships can also be difficult if virtual and real days do not coincide with those of others more often than eclipses of the Jovian satellites. Why wait until “Whit to woo”? The existence of doctors' children provokes the disturbing thought that, in many cases, conception must have taken place with at least one parent asleep or absent.

    Other occupations have this sorted. Postmen, milkmen, bakers, and vicars are larks. Cab drivers, croupiers, restauranteurs, and entertainers are owls. Monks, train drivers, editors, and the military are equine. Poets, artists, and philosophers are whales.

    The human menagerie

    Larks (virtual day 18-24 hours)

    • Need no alarm clock

    • Leap out of bed with a song

    • Burst into action

    • Lots of good work done first thing (they say)

    • Run out of steam after lunch, dozing by 9 pm

    • Do not enjoy theatre or television (they are asleep)

    • On holiday, get up earlier to have more fun

    Owls (virtual day 24-30 hours)

    • Need three alarm clocks

    • Hate getting out of bed

    • Cannot function before 10 am, revived by lunch

    • Fully functional by mid-afternoon, productive in evenings

    • Stay up till 1 or 2 am routinely

    • Cannot sleep because of ideas

    • On holiday, sleep in even later

    Whales (virtual day undefined; it's a virtual year)

    • Torpid all day every day

    • Sleeping and waking blend in a continuum

    • Sleep not correlated with any diurnal cycle

    • Good at moving, eating, and reproducing slowly

    • Energy efficient

    • Contented continuous life

    • Don't need holidays

    Ponies (virtual day close to 24 hours)

    • Never go to bed but sleep and eat standing up

    • Snatch inconspicuous naps

    • Enjoy structured timetables with work and rest periods

    • Bear burdens but can run fast at times

    • On holiday, carry on their work and rest periods

    Hyenas (virtual day 12 hours)

    • Two sleep-work cycles a day

    • Essential siesta

    • Adapted to niches of larks and owls

    • Can be caught napping

    • On holiday, up earlier, out later, longer siesta

    Horses for courses

    • Larks - surgery, anaesthetics, royal college presidents

    • Owls - pathology, radiology, general practice, police surgeons

    • Ponies - medicine, accident and emergency, paediatrics, obstetrics and gynaecology, medical journalism

    • Whales - public health medicine, medical management, neuropathology

    • Hyenas - academic medicine, medical politics

    NHS requirements

    Of course, the NHS needs devoted servants available round the clock to meet patients' predictable and unpredictable needs. But sleepy doctors are poor doctors. NHS doctors should do better. It's not just a question of setting the alarm clock, finding any two socks, and creeping off to work. Patients must have the best, and this means doctors must be in their peak of condition. No one questions that anybody putting the knife or gas to a patient at 8 am should be awake; so all surgeons with morning lists should be larks. Pathologists and radiologists like a lie in and, like mushrooms, flourish in the dark, so they are wise old owls. Medical ponies must seek regular hours and so are suited to shift systems, clinics, sessions, and the armed forces. Time has no meaning in public health medicine and medical management, so there they blow in the fathomless deeps. Other specialties are more diverse: anaesthetists must twitter when the surgeons chirp, but physicians can arrange their hours to suit their burdens so long as they get their oats and a spell in the hay.

    The diurnal down side

    Diurnal variation also has its sinister side. Early birds have always caught the medical worms, and worms also seem to be early. Unlike Gale and Martyn's sample of more typical elderly people,(1) medical larks do seem to get a disproportionate share of the top jobs. London's clubland before dawn has flocks of future presidents of royal colleges taking their austere breakfasts.

    No one has ever been promoted by lying in, even though it's good for you and improves wealth. Of course, there is no point working late if the boss has already dozed off somewhere, unless he has a dedicated owl on the prowl as his number two. Larks, moreover, soar up to the heights and survey the moral high ground. Despite the scientific evidence showing “no justification for early risers to affect moral superiority,”(1) larks disapprove of owls because, in their lofty view, it is simply immoral to remain in bed with the sun shining. Despite anti-owl remarks from larks, owls know that they are industrious old birds while burning the midnight oil. This yawning gap in understanding may never be solved. Early or late means nothing to the whales, who have their minds on next year's annual report. Ponies will do as their master's timetable orders them and their harness permits.

    Adaptive variants

    Rarer medical animals are the carnivores, including hyenas, academics, and medical politicians. These can get up early - often to catch early flights or the media - and still give entertaining after dinner howls or late night interviews. Their explanation is extreme diurnal compression: two days are fitted into every one by the biological expedient of a long refreshing sleep at lunchtime under a tree or in the library. No academic or politico detests a siesta, and the groves abound with soporific carnivores after the lunchtime kill. Similar patterns are under trial in various European cities under the European Union protocol of drinking at lunchtime. Hyenas are successful because they can compete in the niches of both larks and owls, although they find themselves vulnerable to being lunched at lunchtime.

    Career choices

    Young doctors choosing their careers from the scores available should assess their ideal virtual day and see how it fits into the likely timetables of specialties. Fortunately, the wide range of medical specialties can accommodate all biological variants. Doctors should choose those specialties that sympathise with their circadian rhythms. The box gives my suggestions for a timely and sleep conserving career. These will be controversial, but royal college top dogs are welcome to explain which animals they are seeking to train, with what virtual days, and on what planet.

    Planetary dysynchrony

    Many current doctors are in the wrong job and are suffering the predictable ill effects of planetary dysynchrony. Owls are poor in the mornings, larks are dim at night. Whales don't wear watches, and there are not enough ponies to go round the treadmill. Carnivores are laughing sleepily, but they are at the top of the food chain, where the living is easy. So, we doctors mostly work hard, play hard (sometimes, why not?), and sleep hard (whenever possible, prn and nocte). As Fran Leibovitz found, we love sleep because it is both pleasant and safe to use. But try to take it in tune with the music of the spheres.

    All is not lost for those whose days are out of kilter with the times. With the discovery of new planets outside our solar system, hopes are rising of finding ones turning at the right speed for each specialty. Concentration of specialist doctors by selective extraplanetary emigration might suit everybody, giving practical expression to the little worlds in which they think they are living. Until then, hush; leave those sleeping doctors alone. The world is going at the wrong speed, they are in the wrong specialty, and they want to get off.

    Now then, pyjamas, fowling piece, and useful mice are to hand; it's past midnight already; better get some work started.