1 00:00:04,760 --> 00:00:08,030 Jen Oliver: Welcome to the, so that's Why podcast where we unpack the 2 00:00:08,030 --> 00:00:10,190 science behind everyday questions. 3 00:00:10,250 --> 00:00:10,910 I'm Jen. 4 00:00:11,270 --> 00:00:11,840 Chris Smith: I'm Chris. 5 00:00:12,230 --> 00:00:12,800 Matt Edmundson: And I'm Matt. 6 00:00:13,610 --> 00:00:13,910 Jen Oliver: Right. 7 00:00:13,970 --> 00:00:17,870 Today we're answering something that affects everyone with a smartphone, 8 00:00:17,930 --> 00:00:20,300 laptop, or tablet, which is basically. 9 00:00:20,705 --> 00:00:21,245 All of us. 10 00:00:21,815 --> 00:00:24,275 Why does blue light affect sleep? 11 00:00:24,695 --> 00:00:28,325 Because we've all heard we shouldn't scroll through our phones before bed, 12 00:00:28,325 --> 00:00:31,235 but has anyone actually explained why? 13 00:00:31,595 --> 00:00:35,135 Matt Edmundson: So you are talking, Jen, about this nightly ritual of lying 14 00:00:35,135 --> 00:00:39,905 in bed, promising yourself just five more minutes of scrolling and then 15 00:00:39,905 --> 00:00:42,305 suddenly realizing an hour's gone by. 16 00:00:42,830 --> 00:00:48,320 And you've watched 17 videos of cats being scared by cucumbers. 17 00:00:48,830 --> 00:00:49,430 Jen Oliver: Exactly. 18 00:00:49,430 --> 00:00:51,260 I'm guilty of it, I have to admit. 19 00:00:51,860 --> 00:00:52,040 Matt Edmundson: Yeah, me too. 20 00:00:52,040 --> 00:00:54,200 Jen Oliver: Maybe not the cats and cucumbers, but hey. 21 00:00:54,495 --> 00:00:55,880 Matt Edmundson: No, no, definitely those as well. 22 00:00:57,560 --> 00:00:59,180 Jen Oliver: But here's what's fascinating. 23 00:00:59,180 --> 00:01:03,080 For most of human history, the only blue light we encountered after 24 00:01:03,080 --> 00:01:05,960 sunset was moonlight or starlight. 25 00:01:06,170 --> 00:01:07,790 Now we're bathing our eyeballs in it. 26 00:01:08,980 --> 00:01:11,020 Rife right up until we try and sleep. 27 00:01:11,410 --> 00:01:13,750 Chris Smith: And so hopefully by the end of this episode we'll have explained 28 00:01:13,750 --> 00:01:18,730 why your brain interprets that phone screen as a tiny artificial sunrise. 29 00:01:19,210 --> 00:01:22,210 How specialized cells in your eyes communicate directly with your 30 00:01:22,330 --> 00:01:26,140 internal clock and why children are significantly more vulnerable 31 00:01:26,140 --> 00:01:27,490 to these effects than adults. 32 00:01:28,120 --> 00:01:33,310 Matt Edmundson: Plus, we are tackling whether those trendy blue light blocking 33 00:01:33,310 --> 00:01:37,240 glasses actually work or if they're just expensive fashion accessories. 34 00:01:37,240 --> 00:01:37,300 Chris Smith: So. 35 00:01:38,960 --> 00:01:43,790 Let's start with why this matters, and research shows that using an LED 36 00:01:43,850 --> 00:01:48,230 backlit device for just two hours before bed can suppress melatonin production 37 00:01:48,230 --> 00:01:53,210 by over 50% and delay when melatonin starts rising by an hour and a half. 38 00:01:53,795 --> 00:01:57,785 The reason that's significant is when you consider that melatonin is your 39 00:01:57,785 --> 00:01:59,795 body's signal that it's time to wind down 40 00:02:00,365 --> 00:02:03,035 Jen Oliver: and the knock on effects are substantial. 41 00:02:03,335 --> 00:02:08,255 Studies found that around a third of people experience reduced sleep duration 42 00:02:08,255 --> 00:02:13,535 with evening blue light exposure, and half of those report feeling less tired 43 00:02:13,535 --> 00:02:18,365 at bedtime, which sounds positive until you realize it means your body's natural 44 00:02:18,365 --> 00:02:21,275 drowsiness signals are being overridden. 45 00:02:21,980 --> 00:02:26,810 Matt Edmundson: So, so then Jen, all those times I've thought, I'm not tired yet. 46 00:02:26,870 --> 00:02:28,760 I'll just watch one more episode. 47 00:02:29,270 --> 00:02:32,090 My phone apparently is lying to me. 48 00:02:32,090 --> 00:02:33,290 At least that's how I'm interpreting it. 49 00:02:33,830 --> 00:02:36,560 Uh, and so we'll feel betrayed by my own technology. 50 00:02:36,590 --> 00:02:36,980 Mm-hmm. 51 00:02:37,100 --> 00:02:38,720 Chris Smith: That technology betrays in the end. 52 00:02:38,720 --> 00:02:40,340 It's all I've seen that I've seen that movie. 53 00:02:40,430 --> 00:02:40,910 It always does. 54 00:02:41,390 --> 00:02:42,320 Matt Edmundson: It gets you in the end. 55 00:02:43,010 --> 00:02:46,070 Chris Smith: Um, what's particularly concerning is research 56 00:02:46,070 --> 00:02:47,930 showing that pre-B bedtime. 57 00:02:48,755 --> 00:02:51,455 Blue lights exposure can reduce the proportion of deep 58 00:02:51,455 --> 00:02:52,745 sleep throughout the night. 59 00:02:53,015 --> 00:02:55,565 And of course, deep sleep is when your body does its most 60 00:02:55,565 --> 00:02:57,305 important restorative work. 61 00:02:57,605 --> 00:03:01,925 Jen Oliver: Yeah, I mean, we covered in our sleep episode how critical those 62 00:03:01,925 --> 00:03:06,815 deep sleep stages are for things like your memory consolidation, physical 63 00:03:06,815 --> 00:03:11,765 restoration, so disrupting them, it's got consequences well beyond 64 00:03:11,765 --> 00:03:13,175 just feeling groggy in the morning. 65 00:03:14,255 --> 00:03:14,975 Matt Edmundson: Okay, chaps. 66 00:03:14,975 --> 00:03:17,645 So what actually happens biologically? 67 00:03:17,645 --> 00:03:21,905 How does, uh, the blue light from the screen mess with my sleep? 68 00:03:22,655 --> 00:03:25,445 Chris Smith: The key players here are specialized cells in your retina. 69 00:03:25,745 --> 00:03:25,805 Yeah, 70 00:03:25,903 --> 00:03:27,785 Matt Edmundson: so, let me guess, Chris Wright, they've got a 71 00:03:27,785 --> 00:03:32,675 name that I have absolutely no chance of pronouncing whatsoever. 72 00:03:33,305 --> 00:03:34,295 Chris Smith: I knew you'd do this to me. 73 00:03:34,805 --> 00:03:38,825 They are called intrinsically photosensitive retinal ganglion cells. 74 00:03:38,975 --> 00:03:41,525 Matt Edmundson: So yes is the answer to the 75 00:03:41,525 --> 00:03:41,795 question, 76 00:03:41,975 --> 00:03:46,115 Chris Smith: but for today, we'll call them IP RGCs in short. 77 00:03:46,205 --> 00:03:49,145 So these IPRGCs don't contribute much to vision at all. 78 00:03:49,565 --> 00:03:52,925 But they detect ambient light levels and send that information to your brain 79 00:03:53,075 --> 00:03:54,965 and effectively to its master clock. 80 00:03:55,475 --> 00:03:59,705 Jen Oliver: And these cells also contain a light sensitive protein called melanopsin. 81 00:03:59,915 --> 00:04:01,085 And here's the crucial bit. 82 00:04:01,085 --> 00:04:05,945 Melanopsin is most sensitive to blue light wavelengths, specifically 83 00:04:06,155 --> 00:04:09,725 between 460 and 480 nanometers. 84 00:04:10,010 --> 00:04:15,230 And that happens to overlap significantly with the light emitted by our screens. 85 00:04:15,260 --> 00:04:16,430 Matt Edmundson: What a surprise. 86 00:04:16,460 --> 00:04:17,120 Jen Oliver: What a surprise. 87 00:04:17,120 --> 00:04:17,150 Matt Edmundson: I 88 00:04:17,150 --> 00:04:19,801 have no idea what an nanometer is, but what a surprise. 89 00:04:20,161 --> 00:04:24,601 So we've basically got specialized blue light detectors in our eyes that 90 00:04:24,601 --> 00:04:27,211 aren't designed for a Netflix binge. 91 00:04:27,211 --> 00:04:28,291 That's what you're telling me, right? 92 00:04:28,531 --> 00:04:29,791 Chris Smith: Yep, exactly right. 93 00:04:29,791 --> 00:04:33,121 And when Blue Light hits these melanopsin containing cells, 94 00:04:33,391 --> 00:04:37,651 they find signals along a pathway directly to the Supra charismatic 95 00:04:37,651 --> 00:04:39,811 nucleus, which we'll call the SCN. 96 00:04:40,171 --> 00:04:40,256 Jen Oliver: I love that. 97 00:04:40,951 --> 00:04:41,371 Chris Smith: Now this, I 98 00:04:41,371 --> 00:04:42,631 Matt Edmundson: wanna be super charismatic. 99 00:04:42,876 --> 00:04:43,586 Jen Oliver: We've got one, 100 00:04:45,636 --> 00:04:46,546 we've each got one. 101 00:04:47,491 --> 00:04:49,351 Chris Smith: And this SCN, I'm not gonna try and say it again. 102 00:04:49,711 --> 00:04:51,661 Um, it sits in your hypothalamus in the brain. 103 00:04:52,246 --> 00:04:56,866 But if you think of the SCN as your body's central timekeeper, it's coordinating 104 00:04:56,866 --> 00:04:58,636 your 24 hour circadian rhythm. 105 00:04:59,266 --> 00:05:02,806 Jen Oliver: And when the SCN receives these signals saying bright blue light 106 00:05:02,806 --> 00:05:06,076 detected, it interprets this as daytime. 107 00:05:06,226 --> 00:05:10,096 So in response, it sends inhibitory signals that suppress melatonin 108 00:05:10,096 --> 00:05:12,616 in production in the pineal gland. 109 00:05:13,096 --> 00:05:18,826 Matt Edmundson: So my brain then is literally thinking the phone is the sun. 110 00:05:19,516 --> 00:05:19,666 Jen Oliver: Yeah. 111 00:05:19,871 --> 00:05:20,251 Matt Edmundson: Is that 112 00:05:20,251 --> 00:05:20,371 right? 113 00:05:20,371 --> 00:05:20,571 Chris Smith: Yeah. 114 00:05:20,656 --> 00:05:22,336 At a biological level, I'd say yes. 115 00:05:22,336 --> 00:05:26,536 So your circadian systems can't distinguish between natural daylight 116 00:05:26,536 --> 00:05:30,196 and artificial light from screens 'cause both activate the same 117 00:05:30,196 --> 00:05:32,356 pathway under normal circumstances. 118 00:05:32,356 --> 00:05:36,946 As evening approaches and blue light exposure decreases, the pineal gland in 119 00:05:36,946 --> 00:05:41,806 your brain starts producing melatonin about two hours before your usual bedtime. 120 00:05:42,526 --> 00:05:45,171 This rising melatonin signals that your body, that sleep is coming. 121 00:05:45,966 --> 00:05:48,576 Jen Oliver: But when you're exposed to blue light in those evening 122 00:05:48,576 --> 00:05:53,826 hours, this melatonin, the normal rise, it gets suppressed or delayed. 123 00:05:54,096 --> 00:05:57,186 And research has shown that this follows what scientists call 124 00:05:57,186 --> 00:05:59,166 a dose response relationship. 125 00:05:59,466 --> 00:06:02,346 Brighter blue light produces greater melatonin. 126 00:06:03,561 --> 00:06:07,311 Matt Edmundson: So I, I'm, listen, I'm, I'm, I, I had no idea my 127 00:06:07,311 --> 00:06:10,491 casual scrolling was having such a measurable biological impact. 128 00:06:10,731 --> 00:06:11,211 Jen Oliver: I know. 129 00:06:11,301 --> 00:06:14,751 And what makes this particularly relevant to modern life is that blue 130 00:06:14,751 --> 00:06:17,061 lights affects a wavelength specific. 131 00:06:18,036 --> 00:06:20,466 Chris Smith: And interestingly, but probably not surprisingly, the 132 00:06:20,466 --> 00:06:23,496 effects don't disappear immediately when you turn off the screen. 133 00:06:23,826 --> 00:06:28,086 So this suppression of melatonin and the alerting effects can persist for some 134 00:06:28,086 --> 00:06:30,216 time after that light source is removed. 135 00:06:30,576 --> 00:06:33,966 So your circadian system doesn't have an instant reset button, for instance. 136 00:06:34,476 --> 00:06:36,156 Matt Edmundson: So if I. Even. 137 00:06:36,156 --> 00:06:39,756 Even if I sort of put my phone down finally and say at midnight, the damage 138 00:06:39,756 --> 00:06:40,866 is already done for that evening. 139 00:06:40,866 --> 00:06:41,616 Is that what you're saying? 140 00:06:41,706 --> 00:06:43,086 Jen Oliver: To some extent, yes. 141 00:06:43,086 --> 00:06:47,856 So the melatonin delay has already been triggered and this is why recommendations, 142 00:06:47,856 --> 00:06:51,606 fo recommendations focus on like limiting blue light exposure in the hours 143 00:06:51,606 --> 00:06:54,546 before bed, not just at bedtime itself. 144 00:06:55,416 --> 00:06:58,926 Chris Smith: And something that's really interesting for parents to know is 145 00:06:58,926 --> 00:07:02,646 that children are significantly more sensitive to these effects than adults. 146 00:07:02,676 --> 00:07:04,206 So sorry kids, but it's true. 147 00:07:04,221 --> 00:07:04,311 But 148 00:07:05,811 --> 00:07:07,131 Matt Edmundson: sensitive, how, what does that mean? 149 00:07:07,611 --> 00:07:10,641 Jen Oliver: Well, a study comparing children with an average age, age 150 00:07:10,641 --> 00:07:15,981 of about nine to adults around the age of 40, they, it found striking 151 00:07:15,981 --> 00:07:17,241 differences between the two. 152 00:07:17,421 --> 00:07:22,521 So under blue light and enriched lighting conditions, children experience over 153 00:07:22,581 --> 00:07:25,281 80% reduction in melatonin levels. 154 00:07:25,551 --> 00:07:29,091 But adults showed much weaker responses to the same light. 155 00:07:29,601 --> 00:07:30,051 Chris Smith: That's it. 156 00:07:30,051 --> 00:07:32,331 And, um, there are several factors that explain this. 157 00:07:32,331 --> 00:07:36,681 So firstly, children have larger pupils than adults and, and that allows 158 00:07:36,681 --> 00:07:40,491 more light into the eye, but also their crystal eye lenses are clearer. 159 00:07:41,211 --> 00:07:44,811 Yeah, as we age and get a bit more jaded, our lens is naturally yellow, 160 00:07:44,901 --> 00:07:48,471 and this actually filters out some blue light, whereas children's lenses 161 00:07:48,561 --> 00:07:52,821 transmit a high proportion of blue light to those photosensitive cells. 162 00:07:53,181 --> 00:07:56,781 Matt Edmundson: So the very thing that gives kids those beautiful 163 00:07:56,841 --> 00:08:00,306 crystal clear eyes also makes them more vulnerable to the screen. 164 00:08:01,206 --> 00:08:02,226 Which is ironic, isn't it? 165 00:08:02,226 --> 00:08:06,006 Every parent trying to pry an iPad away at bedtime. 166 00:08:06,066 --> 00:08:09,246 Good news is you've now got scientific backing which your children will 167 00:08:09,246 --> 00:08:10,656 fully understand and agree with. 168 00:08:11,376 --> 00:08:11,446 Chris Smith: Yeah, yeah. 169 00:08:11,446 --> 00:08:11,911 Good luck with that. 170 00:08:12,191 --> 00:08:13,591 Jen Oliver: Yeah, no they won't. 171 00:08:14,616 --> 00:08:18,936 But children, they also naturally produce melatonin earlier in the evening. 172 00:08:19,561 --> 00:08:22,531 And in higher amounts than adults, which may make the suppressive 173 00:08:22,531 --> 00:08:23,881 effects more pronounced. 174 00:08:24,181 --> 00:08:28,561 And then the heightened sensitivity is particularly concerning given how 175 00:08:28,561 --> 00:08:30,931 common device use has become before bed. 176 00:08:31,531 --> 00:08:31,771 Chris Smith: Yeah. 177 00:08:31,771 --> 00:08:32,611 And at the other end of the. 178 00:08:33,156 --> 00:08:34,206 Kind of age spectrum. 179 00:08:34,236 --> 00:08:38,616 Older adults may be somewhat less vulnerable because of that lens, uh, 180 00:08:38,736 --> 00:08:39,966 yellowing that I mentioned earlier. 181 00:08:40,296 --> 00:08:43,506 But however, this reduced blue light transmission can actually contribute 182 00:08:43,506 --> 00:08:47,916 to weaker circadian rhythms and the sleep problems common in elderly people. 183 00:08:48,425 --> 00:08:50,945 Jen Oliver: It is worth noting that individual sensitivity 184 00:08:50,945 --> 00:08:52,265 varies quite a bit too. 185 00:08:52,445 --> 00:08:56,945 Some people seem to tolerate evening use with minimal sleep disruption, whereas 186 00:08:57,005 --> 00:09:01,925 others are highly sensitive and there's also genetic variations in clock genes 187 00:09:01,925 --> 00:09:06,785 and differences in melanopsin sensitivity, and they all contribute to this variation. 188 00:09:07,780 --> 00:09:08,560 Matt Edmundson: So some people think. 189 00:09:09,215 --> 00:09:13,295 Really can get away with scrolling before bed whilst others can't, 190 00:09:13,625 --> 00:09:15,695 which hardly seems fair to me. 191 00:09:15,695 --> 00:09:16,895 If I can't and 192 00:09:17,045 --> 00:09:18,035 Jen Oliver: life's not fair, 193 00:09:18,515 --> 00:09:19,145 Matt Edmundson: get over it 194 00:09:19,870 --> 00:09:22,535 Chris Smith: and, and research backs that unfairness. 195 00:09:22,655 --> 00:09:27,245 So research has shown that under identical like conditions, some people experience 196 00:09:27,245 --> 00:09:31,295 near complete melatonin suppression while others show minimal effects. 197 00:09:31,715 --> 00:09:35,075 So if you've noticed that evening screen use doesn't seem to affect 198 00:09:35,135 --> 00:09:37,445 your sleep, you may be less sensitive. 199 00:09:37,745 --> 00:09:38,795 But if you're struggling to sleep. 200 00:09:38,855 --> 00:09:43,145 And, and actually get off to sleep in that, that onset limiting evening 201 00:09:43,145 --> 00:09:44,645 blue light is definitely worth trying. 202 00:09:45,365 --> 00:09:45,605 Matt Edmundson: Mm. Okay. 203 00:09:45,605 --> 00:09:49,775 So what about then guys, the blue light blocking glasses. 204 00:09:49,775 --> 00:09:50,765 I see them everywhere. 205 00:09:51,005 --> 00:09:52,685 Do they actually work? 206 00:09:52,685 --> 00:09:53,465 Should I buy them? 207 00:09:53,675 --> 00:09:54,845 Chris Smith: Yeah, it's an interesting one. 208 00:09:54,845 --> 00:09:59,135 And the research here shows mixed results, but actually on the promising side. 209 00:09:59,135 --> 00:10:02,135 So there's certain studies of involving people with insomnia 210 00:10:02,135 --> 00:10:06,695 have found that wearing am tinted lenses for two hours before bedtime. 211 00:10:07,595 --> 00:10:10,925 Did lead to improvements in sleep quality and duration compared to clear lenses. 212 00:10:11,255 --> 00:10:13,385 Jen Oliver: And the key word there is amber tinted. 213 00:10:13,385 --> 00:10:17,525 So blue light blocking glasses vary enormously in their effectiveness. 214 00:10:17,615 --> 00:10:22,265 Some clear blue blockers filter only about 10 to 30% of blue light, 215 00:10:22,535 --> 00:10:27,965 whereas amber or orange lenses can actually block 90% or more. 216 00:10:28,175 --> 00:10:31,565 The darker tins that block more light tend to show more 217 00:10:31,565 --> 00:10:33,215 consistent benefits in the studies. 218 00:10:34,340 --> 00:10:37,010 Matt Edmundson: Well, I've got some amber tinted ski goggles I could wear to bed. 219 00:10:37,010 --> 00:10:38,270 That might, that might be worth it. 220 00:10:38,420 --> 00:10:38,750 Jen Oliver: Yeah. 221 00:10:38,750 --> 00:10:42,110 I wanna see a photo that, yeah, reading your book with your 222 00:10:42,110 --> 00:10:43,730 ski goggles on or watching 223 00:10:43,850 --> 00:10:44,000 Matt Edmundson: Yep. 224 00:10:44,000 --> 00:10:44,020 Doing that. 225 00:10:44,185 --> 00:10:45,155 Jen Oliver: Looking at your phone. 226 00:10:45,595 --> 00:10:46,760 Chris Smith: I don't want, I don't wanna see a photo. 227 00:10:49,910 --> 00:10:53,180 Um, but you know, for those who can't avoid like evening screen 228 00:10:53,180 --> 00:10:57,260 use, uh, am tin glasses used two to three hours before bed may help. 229 00:10:57,260 --> 00:11:01,130 So it's definitely worth a, a go, but it's not a complete solution 230 00:11:01,130 --> 00:11:03,140 because it's the stimulating content. 231 00:11:03,455 --> 00:11:03,965 Itself. 232 00:11:03,995 --> 00:11:08,585 You know, scrolling social media, catch up on work, emails, watching exciting 233 00:11:08,585 --> 00:11:12,575 shows or boring shows, they all activate our brains regardless of wavelength. 234 00:11:13,025 --> 00:11:13,550 So they all contribute. 235 00:11:14,435 --> 00:11:15,185 Matt Edmundson: Which is fair enough. 236 00:11:15,305 --> 00:11:15,995 Yeah, I get that. 237 00:11:16,445 --> 00:11:19,655 So what about, um, night mode then on phones? 238 00:11:20,255 --> 00:11:21,905 Jen Oliver: Well, research is interesting. 239 00:11:21,905 --> 00:11:26,375 There was a study in 2024 that suggested that overall screen 240 00:11:26,375 --> 00:11:31,355 brightness might matter as much as, or more than the color of light. 241 00:11:31,505 --> 00:11:34,985 So night mode combined with reduced brightness appears more 242 00:11:34,985 --> 00:11:36,670 effective than either alone. 243 00:11:37,170 --> 00:11:38,135 Matt Edmundson: That's interesting, isn't it? 244 00:11:38,135 --> 00:11:42,725 So turning on the night mode, but keeping the brightness like at maximum. 245 00:11:43,235 --> 00:11:45,125 Seems to be like self-defeating, isn't it? 246 00:11:45,125 --> 00:11:48,605 Mm. So, Chris, practical recommendations, you've bound to 247 00:11:48,605 --> 00:11:49,775 have got some, but what are they? 248 00:11:50,135 --> 00:11:51,005 Chris Smith: Yeah, A few things. 249 00:11:51,185 --> 00:11:54,125 I think dimming your screens and, and using warmer color 250 00:11:54,125 --> 00:11:55,145 settings in the evening. 251 00:11:55,595 --> 00:11:56,255 Worth a try. 252 00:11:56,465 --> 00:12:00,905 Considering am tinted glasses, if you must use, uh, devices before bed, 253 00:12:01,265 --> 00:12:06,275 and ideally establishing a consistent time, say two hours before sleep when 254 00:12:06,275 --> 00:12:08,285 you set devices aside altogether. 255 00:12:09,305 --> 00:12:11,165 Jen Oliver: So one thing we should address. 256 00:12:11,255 --> 00:12:16,595 Um, is the persistent myth that blue light from screens damages your 257 00:12:16,595 --> 00:12:20,795 eyes And it's important to note that current evidence doesn't support this, 258 00:12:20,855 --> 00:12:21,695 Matt Edmundson: which is interesting, isn't it? 259 00:12:21,695 --> 00:12:24,425 'cause I, there's a lot of marketing hype out there and I know we're, 260 00:12:24,425 --> 00:12:27,845 we're, you know, we are always down on marketing hype, but there is a lot of 261 00:12:27,845 --> 00:12:30,965 marketing hype out there about protecting your eyes from the harmful blue. 262 00:12:31,660 --> 00:12:33,820 Chris Smith: Yeah, you can get blue light treatment so it can get blue 263 00:12:33,820 --> 00:12:35,320 light well, protection from blue light. 264 00:12:35,320 --> 00:12:37,840 So it's a, it's a complete kind of hypocrisy. 265 00:12:38,170 --> 00:12:42,850 And the confusion comes from laboratory studies using extremely high intensity 266 00:12:42,850 --> 00:12:45,130 blue light on isolated cells. 267 00:12:45,430 --> 00:12:49,930 But the thing is, screens emit far less blue light than natural sunlight does. 268 00:12:50,290 --> 00:12:53,020 The sun delivers up to 1000 times more blue light. 269 00:12:53,540 --> 00:12:56,000 Than you'd get from your electronic device. 270 00:12:56,060 --> 00:13:00,620 So if a screen blue light was genuinely harmful to our retinas, outdoor 271 00:13:00,620 --> 00:13:02,360 sunlight would be catastrophic. 272 00:13:02,750 --> 00:13:02,930 Yeah. 273 00:13:02,930 --> 00:13:04,820 Our eyes, of course, can handle daylight fine. 274 00:13:05,443 --> 00:13:08,983 Jen Oliver: In the American Academy of Ophthalmology, they stated that there's 275 00:13:08,983 --> 00:13:13,513 insufficient evidence that blue light from devices damages eyes, what screens 276 00:13:13,513 --> 00:13:19,513 do, cause its digital eye strain, dry eyes, fatigue, headaches, but that's 277 00:13:19,513 --> 00:13:23,623 from prolonged screen use and reduce blinking, not the blue light itself. 278 00:13:24,133 --> 00:13:25,063 Matt Edmundson: That's interesting, Jen. 279 00:13:25,063 --> 00:13:27,403 So any more recommendations, Chris? 280 00:13:27,973 --> 00:13:30,043 Chris Smith: Yeah, so there are some simple environmental 281 00:13:30,043 --> 00:13:31,183 changes that can help too. 282 00:13:31,213 --> 00:13:35,353 So, switching to warm colored, dim lighting in the evening or bulbs 283 00:13:35,353 --> 00:13:37,243 with, uh, lower color temperatures. 284 00:13:37,738 --> 00:13:41,188 That reduces blue light exposure without requiring glasses or screen changes. 285 00:13:41,428 --> 00:13:43,978 Jen Oliver: Yeah, and don't over overlook the power of getting 286 00:13:43,978 --> 00:13:45,208 bright light during the day. 287 00:13:45,418 --> 00:13:48,748 So getting outside for natural daylight, especially in the morning, that 288 00:13:48,748 --> 00:13:52,438 actually strengthens your circadian rhythms, and so it might reduce your 289 00:13:52,438 --> 00:13:54,628 sensitivity to evening light disruption. 290 00:13:54,838 --> 00:13:57,178 It's not just about avoiding blue light at night. 291 00:13:57,178 --> 00:13:59,428 It's about getting enough at the right times. 292 00:13:59,728 --> 00:14:03,778 Matt Edmundson: So morning sunlight then is my friend, if I understand it. 293 00:14:04,108 --> 00:14:07,198 But late night phone scrolling is perhaps a frenemy. 294 00:14:08,428 --> 00:14:09,568 I just like that word frenemy. 295 00:14:09,568 --> 00:14:10,138 Had to get it in. 296 00:14:11,308 --> 00:14:13,288 Chris Smith: That's, it's a bit too Gen Z for me. 297 00:14:15,088 --> 00:14:15,488 Jen Oliver: We're done with the kids 298 00:14:15,488 --> 00:14:15,773 Matt Edmundson: Z or Gen Z. 299 00:14:15,773 --> 00:14:16,053 Jen Oliver: It's okay. 300 00:14:16,133 --> 00:14:16,253 Matt Edmundson: I 301 00:14:16,253 --> 00:14:16,453 dunno, 302 00:14:16,453 --> 00:14:16,473 Chris Smith: I dunno 303 00:14:17,458 --> 00:14:18,598 which generation we're in these days. 304 00:14:19,228 --> 00:14:20,518 Alpha, beta, I, I dunno. 305 00:14:20,518 --> 00:14:22,588 Um, but no, you, you're right. 306 00:14:22,588 --> 00:14:25,558 I mean the real concern here with blue, blue light is. 307 00:14:26,473 --> 00:14:29,623 The, uh, circadian disruption rather than eye damage itself. 308 00:14:29,893 --> 00:14:32,473 And this connects to everything else we've discussed on this podcast. 309 00:14:32,473 --> 00:14:37,303 So sleep quality affects cognitive function, mood, metabolism, 310 00:14:37,453 --> 00:14:38,983 immune function, everything. 311 00:14:39,523 --> 00:14:42,553 Jen Oliver: And the circadian system also influences when we 312 00:14:42,553 --> 00:14:46,093 feel hungry, when we have energy, and when hormones are released. 313 00:14:46,093 --> 00:14:50,023 So disrupting it with mistimed light exposure can have ripple 314 00:14:50,023 --> 00:14:51,943 effects throughout your biology. 315 00:14:53,068 --> 00:14:54,043 Chris Smith: The good news. 316 00:14:54,553 --> 00:14:57,013 If there is some good news is that blue light exposure during 317 00:14:57,013 --> 00:14:58,693 the day is actually beneficial. 318 00:14:58,963 --> 00:15:02,233 It promotes alertness and it helps reinforce strong circadian rhythms. 319 00:15:02,233 --> 00:15:06,193 As Jen was saying, it's specifically the evening exposure that causes these 320 00:15:06,193 --> 00:15:07,243 problems that we're talking about. 321 00:15:07,933 --> 00:15:10,813 Matt Edmundson: Yeah, and listening to you guys talk, I'm realizing maybe just 322 00:15:10,813 --> 00:15:15,013 five more minutes of scrolling might be costing me more than I thought. 323 00:15:15,013 --> 00:15:19,903 So not just lost sleep, but lower quality of sleep when I do finally drop off. 324 00:15:20,683 --> 00:15:23,563 Jen Oliver: So why does blue light affect sleep? 325 00:15:24,268 --> 00:15:27,568 Chris Smith: Blue light affects sleep because specialized cells in your 326 00:15:27,568 --> 00:15:31,768 retina containing melanopsin are highly sensitive to blue wavelengths. 327 00:15:32,128 --> 00:15:36,118 When these cells detect blue light, they signal to your brain's master clock 328 00:15:36,118 --> 00:15:39,748 that it's daytime, which suppresses melatonin production and delays your 329 00:15:39,748 --> 00:15:41,818 body's natural wind down process. 330 00:15:42,778 --> 00:15:47,638 Matt Edmundson: So every time I check my phone at 11:00 PM my brain genuinely 331 00:15:47,638 --> 00:15:49,738 thinks I've glimpsed the sunrise. 332 00:15:49,768 --> 00:15:53,638 And I wonder, I can't sleep after a scrolling session. 333 00:15:54,328 --> 00:15:58,138 Jen Oliver: Now you know why dimming your screens using warmer light settings 334 00:15:58,168 --> 00:16:02,698 and ideally putting devices away a couple of hours before bed can make 335 00:16:02,698 --> 00:16:04,738 such a difference to sleep quality. 336 00:16:05,038 --> 00:16:09,118 Your circadian system simply can't tell the difference between 337 00:16:09,118 --> 00:16:10,978 your phone and the morning sun. 338 00:16:11,848 --> 00:16:13,078 That's it for this week. 339 00:16:13,138 --> 00:16:15,328 Make sure you hit that subscribe button. 340 00:16:15,508 --> 00:16:19,438 We're unpacking the science behind everyday questions each week. 341 00:16:19,768 --> 00:16:22,318 Tell us in the comments what you'd like us to explore. 342 00:16:22,708 --> 00:16:26,038 Thanks for geeking out with us, but for now, that's it from me. 343 00:16:26,548 --> 00:16:27,388 Matt Edmundson: That's it from me, 344 00:16:27,583 --> 00:16:28,648 Chris Smith: and that's it from me. 345 00:16:29,288 --> 00:16:29,968 Jen Oliver: Bye for now.