Program: Is daylight saving time bad for us?

Tegan Taylor: Norman, something very exciting happens for you and me, on Sunday actually, this coming week.

Norman Swan: For me it's not so exciting, but for you it is because we're back in sync.

Tegan Taylor: Well, sorry, do you not care about being in sync with me? 

Norman Swan: Well, look, I do deeply, but I wish you joined us on the rest of the east coast in Australia in daylight saving, but you Queenslanders are recalcitrant. 

Tegan Taylor: That's what they say, an hour and 10 years behind, or…I can't remember now, it's something slightly insulting, but I agree, I think we should have daylight savings here. Maybe I should run for parliament on that basis. 

Norman Swan: Yeah, that'll guarantee you staying at the ABC for a while, including if you ran for it in Western Australia, who equally hate daylight savings. 

Tegan Taylor: But one of the things that crops up a lot around daylight savings is whether it's bad for us. So let's get stuck into it.

Norman Swan: On What's That Rash?.

Tegan Taylor: The show where we answer the health questions everyone is asking. So this week, the question comes from Laura in New South Wales, but I think it's a question a lot of people have. Laura says, 'Is daylight savings doing any harm to our health? With the sun now getting up later, it's harder to wake my three-year-old in time for the daily commitments, while at night he's still cruising around till the sun goes down. It seems our natural sleep cycle suffers while daylight savings drags on for way too long.' Laura is definitely not the first person to have trouble with a three-year-old's sleep, and certainly not the first person to struggle with daylight savings.

Norman Swan: No. So where should we start? Should we start with the way the body works and how our rhythm works, and then see how that reverses back into daylight saving? What do you think?

Tegan Taylor: Sure, because I do think a three-year-old is a good kind of indicator, time means nothing to them, they're just responding to their body's cues, biological cues, constantly. So what's happening in the body? And then, how do we inflict clocks on top of that?

Norman Swan: Every living species on the planet has a clock entrained into the 24-hour daylight cycle, and the clock has different influences on their metabolism. So you'll find that flowering in certain plants is geared to the length of the day. We live on a planet which has got day/night cycles, and our bodies are entrained in that. And if you go to humans, we have a centralised clock in the brain above our eyes, in what's called the anterior hypothalamus. The hypothalamus controls all sorts of things in our body; appetite, temperature and so on. And there, in the anterior hypothalamus, there's a bundle of nerves called the suprachiasmatic nucleus, SCN, which responds to light passing through the optic nerve, which goes nearby, and in response to that, this nucleus stimulates or inhibits the production of melatonin, which induces sleep or not.

Tegan Taylor: Ah yes, melatonin. We talked about it in an episode of What's That Rash? which I think is called 'Melatonin', if people want to go back and refresh their memory.

Norman Swan: But it's a master clock, almost every metabolic process in the body, including our temperature, varies according to the day/night cycle. Rectal temperature, in other words the temperature measured in your bum, is at its lowest in the morning. Now I must tell you a fascinating study to do with rectal temperature…

Tegan Taylor: Go on. I never want to skip a single story about rectal temperature ever.

Norman Swan: By the way, mastication comes into this too. So our muscle performance…I'm slightly contradicting myself from earlier, but muscle performance, particularly in men, seems to be higher in the afternoon than it is in the morning. And one experiment tried to see whether or not if you took an ice bath in the evening to return your rectal temperature to what it is in the morning, could you change your muscle output?

Tegan Taylor: So like, literally cool your butts and let's see how you go.

Norman Swan: That's right, and in this vast study of 10 men, their muscle output reduced in the evening. So all these sports guys having ice baths in the afternoon and they have training afterwards, it could be screwing them up. Anyway…

Tegan Taylor: I love that someone had that idea and they decided to test it out. People don't have ice baths before they train, they usually have it after they train.

Norman Swan: Afterwards, it's true, thank you for correcting me. We're obsessed with facts here on…but let's get closer to daylight saving now, and a concept called free running time. So every organism on the planet is entrained in this 24-hour day/night cycle. 

Tegan Taylor: Well, it's actually not exactly 24 hours, is it? For humans, at least, it's a little off, but the clock resets each day when the Sun decides to come up.

Norman Swan: Correct. But if you go into a cave, the free running time of your cycle moves more towards 25 hours. So our natural cycle, independent of the cues from day and night, is about. 25 hours, and this tallies with studies as they are about the harms or benefits of daylight saving does tie into that. 

Tegan Taylor: So in daylight savings, basically we inflict clocks on our bodies in the first place, time is a construct, and then we mess with those during daylight savings. What happens in spring in daylight savings is that we move the clocks forward an hour to give ourselves an extra hour of daylight during the day. But what that means is we lose an hour of sleep that night when we change it, and then the reverse happens in autumn.

Norman Swan: You gain an hour of sleep, whereas in springtime, while you might feel the day is longer because you can get out and about after you get back from work (showing my bias now towards daylight saving), the day feels longer, in fact for a short period of time the day is actually…your body detects that as a shorter day, and that's going against the natural, if you like, cycle in your body, which is longer than 24 hours.

Tegan Taylor: Before we get into the health effects or not. Do you want me to tell you how we came to have daylight savings? 

Norman Swan: I'd love to know.

Tegan Taylor: So it's a more recent invention than I realised, and it's also an invention closer to home than I realised. Do you know who invented daylight savings? 

Norman Swan: It was a New Zealander, wasn't it? 

Tegan Taylor: It was! Well, he was actually born in the UK, but he lived his adult life in New Zealand. What sort of profession would you expect a daylight savings inventor to have? 

Norman Swan: Probably not a farmer.

Tegan Taylor: No, not a farmer. We know farmers are famously opposed to daylight savings, which we'll get into later. He was an entomologist. He was an insect studier.

Norman Swan: So he was in trained in the day/night cycle of insects. 

Tegan Talor: It wasn't his day job, so he had shift work, and he liked the fact that he had leisure time to collect insects after he finished his shift. And so he really started to value after-hours daylight.  Then in 1895 he presented a paper to the Wellington Philosophical Society proposing a two-hour daylight saving shift. Everyone laughed at him,, they thought it was dumb. But some years later, in 1927 they tried it out, and it became quite popular in war time because it was a measure to conserve fuel and energy, because the daylight hours stretched into the evening, reducing the need for artificial lighting, at least in the summertime.

It went through the wartime years, came back again in the '40s during the other war. And then from about 1971 it was introduced in Australia, starting with New South Wales. And so now we know that people, mostly along the eastern seaboard, except for Queensland, have daylight savings, WA doesn't, and also the Northern Territory. So that's the little potted history of daylight savings time. For something that is pretty well established in lots of different countries around the world, it is highly controversial, especially in Australia.

Norman Swan: Yeah, and in other countries as well. So there's a growing sense in the United States and other countries that is it worth doing. It's got this historical notion to it, but is there more harm than good? So it's an active debate in many parts of the world. And whilst I'm thoroughly in favour of it, it's particularly annoying in Australia when Queensland, for example, on the east coast, is out of sync with the rest of the east coast. 

Tegan Taylor: But you can see why. I think the bigger difference you have between your summer hours and your winter hours, the more sense it makes, that if it is light late into the evening, that's really great. In Queensland, the further north you go in the NT, and for the vast majority of the land mass of WA, there isn't a huge amount of difference between your daylight hours in summer and in winter, so changing the clocks further kind of makes less sense.

Norman Swan: It's also lifestyle. In Western Australia, if you're living on the coast, the optimal time to go to the beach is actually first thing in the morning. If you talk to people in Western Australia, this is a very hot state, so is Queensland, and there is no pleasure in being out and about for longer in the day, because you changed to daylight saving. In fact, it's quite uncomfortable. Our most comfortable time of the day is the morning, and you're kind of depriving us of that because you're moving the clock.

Tegan Taylor: See, I would put it the other way. I would rather get up earlier. If you make five o'clock six o'clock, and then I get up at five o'clock, I get an even earlier morning, an even better time of day. 

Norman Swan: I'm on your side on this one. But they also complain about things like, well, our kids have to go to school in the dark. Well, get over it. 

Tegan Taylor: It's easy for you to say!

Norman Swan: It is easy for me to say, I grew up in Scotland, and for about six months of the year I went to school in the dark and came home in the dark. Somehow Scottish people survived this and, you know, we've got a few Nobel laureates and inventions of the steam engine. You know, there's lots of things that Scots did that…

Tegan Taylor: You never would have been able to invent the steam engine if it hadn't been for the hardship of getting up in the dark.

Norman Swan: Well, that's right, you've got nothing else to think about than just being…but anyway, seriously, there are all sorts of reasons, but you've got to respect people's views on this, and it's so uniform in farming communities that you have to listen to them. But I mean, what we're being asked here is whether or not there's a risk here. 

Tegan Taylor: Yeah, the health risk. And for something that's only an hour, I feel like it's a small change, it happens over a huge number of people. So we actually are able to discern whether there is a health effect here.

Norman Swan: If I were to summarise what the research suggests is that when the clock goes forward in spring, there's an increased risk of things like stroke and heart attacks. And then that that's kind of reversed in the autumn change where heart attacks tend to reduce, strokes trying to reduce, and when you balance it out over the year, there's actually no difference.

Tegan Taylor: Say that to the person who has the stroke though, right? Like, it must be pretty hard to think that there could be even a slight causative factor there. 

Norman Swan: True. Studies do suggest there is a problem in spring, but in fact there's a protection in autumn. 

Tegan Taylor: There is one health effect that I really wanted to ask you about, Norman, because we've talked about heart attack and stroke. I saw a study that looked at embryo transfers and the chances of them leading to a live birth in older patients, and there was an effect from daylight savings. 

Norman Swan: Yeah. I mean, these are small studies. Could it be that the embryologist is more awake or more asleep during that time? Is it the embryo itself? Who knows.

Tegan Taylor: So what's actually happening here? How is one hour of sleep making such a big difference? And what kind of period after the daylight saving change are we looking at?

Norman Swan: It's fairly short-term. What we didn't talk about when we talked about the biology of our circadian clocks is that our circadian clocks are affected by all sorts of things. So it's not just the day/light cycle. It's affected by how we live and how we exercise and how we eat. For example, if you exercise at daybreak, that readjusts your clock so people who exercise and adjust their exercise time according to the new day, they probably have fewer effects on the body clock than people who put off their exercise, your meal times makes a difference to the body clock, how often you chew…

Tegan Taylor: Okay, this is the mastication that you promised. Please explain.

Norman Swan: You've got to take some of this with not just a pinch of salt, but is that you masticate more in the morning than in the evening…

Tegan Taylor: Do I?

Norman Swan: And that has an effect on digestion. I suppose that depends on whether you're rushing to work because you've slept in because it's dark.

Tegan Taylor: Breakfast is my most favourite meal of the day. But tell me how you calculate my jaw movements across the day, Norman.

Norman Swan: These are experimental studies. I wouldn't dare to check your mastication, and it's such a personal thing, your mastication habits, I wouldn't even deem to have a go at this. But the point I'm making here is this is behavioural as well as biological. And if your behaviour changes according to the new daylight saving time, you're much less likely to feel an impact. 

But there are all sorts of things that increase the risk of heart attacks; the time you go to work, whether you're driving the car, whether you're getting the bus, and morning is a time when heart attacks are more common than in the afternoon. Nobody's entirely sure why. And it could be that the change in the clock, even though it's minor, does shift that, both behaviourally and biologically. And then in autumn, it goes in a much more favourable direction. 

And the other thing I want to add about children, since we've talked about free-running three-year-olds, is that some people argue, and there is research to suggest it, which includes Australian data involving 23,000 children aged 15 to 16, 15 studies, nine countries, it suggests that daylight saving increases the amount of physical activity that children take, simply because they're out during a longer day. 

Tegan Taylor: So those studies were done in New South Wales and Victoria. It's hot in the afternoon in summer in Queensland and in WA, hotter than it tends to get in the southern states. Could that perhaps be a deterrent?

Norman Swan: It might be, and I haven't seen a dataset, but it could be.

Tegan Taylor: Give us your datasets, folks. So coming back to Laura's question; is daylight savings doing any harm to our health? It kind of sounds like maybe a little bit yes, but is it a big enough effect to change it? You're obviously biassed, you've already declared your conflict of interest here. 

Norman Swan: Yeah, I've declared my bias. I mean, the problem with…in terms of health effects, it's swings and roundabouts, and the net effect is…even though it's a disturbing thought, is that over a year, daylight saving does not change the epidemiology of heart disease overall. So in a state where you've got daylight saving, you've not necessarily got more heart attacks than a state that doesn't. In fact Queensland is quite an unhealthy state by national standards in Australia and they don't have daylight saving. I'm not blaming lack of daylight saving on that, but you can't argue that New South Wales and Victoria or Tasmania are unhealthier states than states that don't have daylight saving. The net effect is probably zero.

Tegan Taylor: Fascinating twists and turns. Laura, thank you so much for giving us the chance to dig into this.

Norman Swan: Yeah, it's a shame that Tegan and I agree so violently on this, but keep masticating.

Tegan Taylor: It would have been better if we'd come to blows. Well, if you have a question that you'd like to ask us, you can email us. The email address is thatrash@abc.net.au, which is also where you can send us your feedback on our previous episodes, which is what a few people have done, Norman, in response to our episode last week on wearing glasses and whether they make your vision worse.

Norman Swan: That's right. So Jane writes…

Tegan Taylor: Jane says, 'My husband definitely falls into the category of feeling he needs to wear his glasses even after cataract surgery, because he's worn them most of his life.' Oh, so this was in relation to the conversation that you had with your eye doctor, Norman, when you went to have corrective vision surgery.

Norman Swan: Yeah, we had a discussion. I had premature cataracts because of eye surgery, and the discussion was, what strength of intraocular lens should I have? Should I get full correction so I could see perfectly without specs? And my ophthalmologist said, look, you've been wearing specs since the age of 10, and his experience was that people who've been wearing specs most of their lives feel uncomfortable without them, it's part of their identity. So he under-corrected my vision so that I needed to wear specs, although my vision got a lot better, and I'm glad I made that decision. And that's really what happened to Jane's husband.

Tegan Taylor: Well, I think his surgeon said he wouldn't need to wear specs. But after trying diligently for a month, Jane's husband felt the intraocular lenses were not precise enough. Jane says, 'I suspect a high degree of psychological aspect to this.' And then she adds, 'On the flip side, I often find it difficult to get used to friends who have had cataract surgery no longer being their glasses-wearing self.' Oh, and she signs off, 'Of course I cannot fail to mention, I love your show.' We love you too, Jane.

Norman Swan: And another Jane.

Tegan Taylor: Yeah, two Janes. It's actually two Janes and a Janet in the mailbag today. Second Jane, Jane number two says, 'I have astigmatism and have worn glasses since age five, and like Norman, I still remember the incredible impact and suddenly being able to see the blackboard at school.' Jane says, 'At 64 I had my cataracts removed and an intraocular lens placed that corrected my astigmatism.' Jane's ophthalmologist has given her distance vision in her left eye and reading vision in her right eye. Jane is now glasses free, 'and have found it to be equally as liberating as my five-year-old experience. Now I can swim and find my towel on the beach, exercise without fogging up, and read the Herald in dim light and see birds through the binoculars.'

Norman Swan: So this trick of having your vision in one eye different from the vision in the other eye is actually quite common in people who are on television, so that they can read the script on the desk and read the script on the teleprompter. So they often have different intraocular lenses when you get to that point. I get very nauseous at that, so I've got the same prescription in both eyes. But a great story. I mean, my swimming has been transformed by having prescription goggles, I must say.

Tegan Taylor: Oh, okay, that's cool. I remember that from the movie Notting Hill. He goes to the movies with his goggles on because he can't find his classes.

Norman Swan: Yeah, but one day my partner took my goggles by mistake and she couldn't see a thing.

Tegan Taylor: Oh, I need to read the final line of Jane number two's email. She says, 'I certainly can see my wrinkles now, but I love that my four daughters now know that I have blue eyes.'

Norman Swan: And Janet, who writes from Toronto.

Tegan Taylor: Toronto. Janet says she needed to get glasses in her 40s, but she never liked wearing them. In her 50s she developed cataracts and got corrective implants. 'That was about 10 years ago. I haven't worn glasses since. I can't imagine electing to under correct in order to still require glasses, but neither was I adapted to them as a child. Anyway, just sharing my story, since yours entertained me in my insomnia hours this morning.'

Norman Swan: Thanks, Janet, always great to hear from our Canadian subscribers and listeners. We have lots of them, and they do have insomnia because when they go to air on linear radio on CBC, it's very early in the morning Canada time.

Tegan Taylor: You love to hear from a fellow insomniac too, don't you, Norman?

Norman Swan: I do, I do. I mean, the point here, just to move on from our spectacle story, is your ophthalmologist is giving you the choice, and knowing that there is a choice, you don't have to get full correction, or you can get full correction, which is a wonderful thing for many people.

Tegan Taylor: Well, Jane, Jane and Janet, and people with other names, thank you for sending in your emails to us, we love reading them. If you've got feedback, you can email us, thatrash@abc.net.au.

Norman Swan: As long as there's a J in your name, we'll answer it.

Tegan Taylor: And we'll see you next week. 

Norman Swan: See you then.