0:00:00.083,0:00:03.851 Many of us like to start the day[br]with a cup of coffee 0:00:03.875,0:00:06.893 and perhaps end the day[br]with a glass of wine 0:00:06.917,0:00:09.143 or some other kind of alcoholic drink. 0:00:09.167,0:00:11.934 But it turns out[br]that these two substances, 0:00:11.958,0:00:16.768 alcohol and caffeine,[br]can have surprising impacts on our sleep. 0:00:16.792,0:00:19.331 [Sleeping with Science] 0:00:19.375,0:00:21.809 (Music) 0:00:21.833,0:00:24.101 Let's start with caffeine. 0:00:24.125,0:00:26.309 Caffeine is in a class of drugs 0:00:26.333,0:00:29.684 that we call the psychoactive stimulants. 0:00:29.708,0:00:33.101 And everyone knows that caffeine[br]can make them more alert. 0:00:33.125,0:00:35.143 It can wake them up. 0:00:35.167,0:00:37.434 But there are at least two additional, 0:00:37.458,0:00:39.684 hidden features of caffeine 0:00:39.708,0:00:42.434 that some people may not be aware of. 0:00:42.458,0:00:47.059 The first is the duration[br]of action of caffeine. 0:00:47.083,0:00:49.059 Caffeine, for the average adult, 0:00:49.083,0:00:51.559 will have what we call a half-life 0:00:51.583,0:00:53.851 of about five to six hours. 0:00:53.875,0:00:57.351 What that means is that[br]after about five to six hours 0:00:57.375,0:01:00.601 50 percent of that caffeine that you had 0:01:00.625,0:01:03.643 is still circulating in your system. 0:01:03.667,0:01:07.976 What that also means[br]is that caffeine has a quarter-life 0:01:08.000,0:01:10.976 of about 10 to 12 hours. 0:01:11.000,0:01:14.018 In other words, let's say[br]that you have a cup of coffee 0:01:14.042,0:01:16.393 at 2pm in the evening. 0:01:16.417,0:01:20.143 It could be that almost[br]a quarter of that caffeine 0:01:20.167,0:01:24.059 is still swilling around[br]in your brain at midnight. 0:01:24.083,0:01:27.643 And as a result, it can make[br]it harder for an individual 0:01:27.667,0:01:31.184 to fall asleep or even stay asleep soundly 0:01:31.208,0:01:32.684 throughout the night. 0:01:32.708,0:01:35.434 So that's the first feature of caffeine. 0:01:35.458,0:01:37.684 The second issue with caffeine 0:01:37.708,0:01:41.351 is that it can change[br]the quality of your sleep. 0:01:41.375,0:01:42.976 Now some people will tell me 0:01:43.000,0:01:44.809 that I'm one of those individuals 0:01:44.833,0:01:47.309 who can have an espresso with dinner, 0:01:47.333,0:01:50.559 and I fall asleep fine,[br]and I can stay asleep. 0:01:50.583,0:01:53.059 But even if that's true, it turns out 0:01:53.083,0:01:56.434 that caffeine can actually[br]decrease the amount 0:01:56.458,0:01:59.893 of deep, non-rapid eye movement[br]sleep that we have, 0:01:59.917,0:02:03.059 stages three and four of non-REM sleep. 0:02:03.083,0:02:06.018 That's that sort of[br]restorative deep sleep. 0:02:06.042,0:02:09.393 And as a consequence,[br]you can wake up the next morning, 0:02:09.417,0:02:11.101 and you don't feel refreshed, 0:02:11.125,0:02:13.809 you don't feel restored by your sleep. 0:02:13.833,0:02:15.434 But you don't remember waking up, 0:02:15.458,0:02:18.018 you don't remember[br]struggling to fall asleep, 0:02:18.042,0:02:20.226 so you don't make the connection, 0:02:20.250,0:02:23.018 but nevertheless[br]you may then find yourself 0:02:23.042,0:02:26.726 reaching for two cups of coffee[br]in the morning to wake up 0:02:26.750,0:02:28.309 rather than one. 0:02:28.333,0:02:33.143 So that's caffeine,[br]but now let's move on to alcohol, 0:02:33.167,0:02:35.059 because alcohol is perhaps one 0:02:35.083,0:02:39.143 of the most misunderstood[br]sleep aids out there. 0:02:39.167,0:02:42.559 In fact, it's anything but a sleep aid. 0:02:42.583,0:02:44.893 And it can be problematic for your sleep 0:02:44.917,0:02:47.226 in at least three different ways. 0:02:47.250,0:02:49.684 First, alcohol is in a class of drugs 0:02:49.708,0:02:52.184 that we call the sedatives. 0:02:52.208,0:02:55.059 But sedation is not sleep. 0:02:55.083,0:02:57.309 And studies teach us that those two things 0:02:57.333,0:02:59.309 are really quite different. 0:02:59.333,0:03:00.934 Sedation is a case 0:03:00.958,0:03:04.393 where we're simply[br]switching off the firing 0:03:04.417,0:03:07.809 of the brain cells,[br]particularly in the cortex. 0:03:07.833,0:03:10.476 And that's not natural sleep. 0:03:10.500,0:03:13.434 In fact, during deep[br]non-rapid eye movement sleep, 0:03:13.458,0:03:17.976 for example, the brain has[br]this remarkable coordination 0:03:18.000,0:03:20.684 of hundreds of thousands of cells 0:03:20.708,0:03:23.018 that all of a sudden fire together, 0:03:23.042,0:03:24.476 and then they all go silent, 0:03:24.500,0:03:27.434 and then they all fire together,[br]and then they go silent, 0:03:27.458,0:03:30.434 producing these big, powerful brainwaves 0:03:30.458,0:03:32.768 of deep non-REM sleep. 0:03:32.792,0:03:34.393 And so that's the first way 0:03:34.417,0:03:36.809 in which alcohol can be problematic. 0:03:36.833,0:03:40.268 We're mistaking sedation for deep sleep. 0:03:40.292,0:03:42.518 The second problem with alcohol 0:03:42.542,0:03:45.643 is that it can actually[br]fragment your sleep. 0:03:45.667,0:03:49.643 Alcohol can actually trigger[br]and activate during sleep 0:03:49.667,0:03:52.309 what we call the fight or flight branch 0:03:52.333,0:03:53.893 of the nervous system, 0:03:53.917,0:03:56.559 which will therefore[br]wake you up more frequently 0:03:56.583,0:03:58.184 throughout the night. 0:03:58.208,0:04:00.476 And alcohol can even increase the amount 0:04:00.500,0:04:04.184 of alerting chemicals[br]that are released by the brain, 0:04:04.208,0:04:06.934 once again fragmenting your sleep. 0:04:06.958,0:04:11.018 The third and final issue[br]with alcohol and sleep 0:04:11.042,0:04:13.393 is that alcohol can actually block 0:04:13.417,0:04:16.768 your rapid eye movement sleep,[br]or your dream sleep. 0:04:16.792,0:04:19.476 And as we'll learn in subsequent episodes, 0:04:19.500,0:04:22.393 REM sleep, or rapid eye[br]movement sleep, dream sleep, 0:04:22.417,0:04:24.559 provides a collection of benefits, 0:04:24.583,0:04:26.726 things such as your emotional 0:04:26.750,0:04:30.101 and mental health, even creativity. 0:04:30.125,0:04:33.851 Now I'm not here[br]to tell anyone how to live. 0:04:33.875,0:04:35.851 I don't want to be puritanical. 0:04:35.875,0:04:37.559 I'm just a scientist. 0:04:37.583,0:04:40.393 What I want to try and do is provide you 0:04:40.417,0:04:43.101 with the information[br]about the relationship 0:04:43.125,0:04:46.226 between caffeine and alcohol on your sleep 0:04:46.250,0:04:49.309 so then you can make an informed choice 0:04:49.333,0:04:52.059 as to how best you want to live your life 0:04:52.083,0:04:54.833 when you're trying to[br]prioritize your sleep health.