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Caffeine and Sleep: Garmin Fenix 3 Sleep Tracking

by Daniel Puddick
Man Taking A Caffeine Nap At His Desk With Coffee In Hand

After listening to a Stuff You Should Know podcast, I thought I would try a change in my caffeine habits. 

For sleep tracking, I currently use a Garmin Fenix 3. The Garmin Fenix 3 is a sports watch and activity tracker that does everything you need and more. From dedicated triathlon training to running, step counting, and of course for this test sleep tracking. A recent update from Garmin means you do not need to tell the watch when you go to sleep. It knows! 

What's required for this test?

Garmin Fenix 3

Garmin Fenix 3

Less Coffee

And a lot less coffee

Caffeine Before Sleep

It takes a regular coffee or tea drinker to know just how tough it is to cut back on the caffeine intake. I thought it would be hard but it was surprisingly easy for me. So why the test? On the podcast, they reminded me that caffeine has a half-life of 6 hours, which means that after 6 hours you still have 50% of the effect in your system. So if you have a caffeinated drink at 3pm and one at 5pm then this is essentially the same as having a full coffee at around 10pm. You may fall asleep with no problems, but your deep sleep will be affected. 

From Garmin you get a breakdown of deep and light sleep. Plus awake time, so in theory seeing if a 2 week test will make any difference will be fairly easy to measure. 

Is Caffeine Affecting Your Sleep?

From my reading on the NHS and various other reputable sites, caffeine may affect your sleep, but not for everyone as everyone's body treats caffeine differently. My results from Garmin in the two weeks leading up to the test were as follows:

Date Deep Sleep Light Sleep % of Deep Sleep
1/5/2016 2:40:00 5:08:00 34.19%
1/6/2016 3:03:00 4:17:00 41.59%
1/7/2016 2:33:00 4:43:00 35.09%
1/8/2016 3:28:00 4:16:00 44.83%
1/9/2016 3:19:00 3:32:00 48.42%
1/10/2016 4:22:00 6:12:00 41.32%
1/11/2016 2:33:00 5:21:00 32.28%
1/12/2016 2:44:00 5:32:00 33.06%
1/13/2016 2:39:00 5:36:00 32.12%
1/14/2016 2:26:00 5:20:00 31.33%
1/15/2016 2:05:00 5:57:00 25.93%
1/16/2016 3:34:00 5:14:00 40.53%
1/17/2016 2:38:00 5:26:00 32.64%
1/18/2016 2:59:00 4:31:00 39.78%
1/19/2016 2:37:00 4:39:00 36.01%

The test kicked off with the following rules. Going from 10+ cups of tea and coffee per day up until about 5pm to just one in the morning first thing. No other caffeine. Without other people to compare my stats to, I am just looking for a blame why my deep sleep is just a little over half (but very broken up through the night). 

So bring on two weeks of sleep tracking with just one cup in the morning.

Date Deep Sleep Light Sleep % of Deep Sleep
1/20/2016 2:30:00 4:51:00 34.01%
1/21/2016 3:35:00 4:42:00 43.26%
1/22/2016 2:41:00 5:46:00 31.76%
1/23/2016 3:02:00 4:45:00 38.97%
1/24/2016 2:31:00 5:10:00 32.75%
1/25/2016 2:10:00 3:39:00 37.25%
1/26/2016 2:47:00 5:14:00 34.72%
1/27/2016 2:26:00 4:50:00 33.49%
1/28/2016 4:12:00 3:47:00 52.61%
1/29/2016 2:10:00 5:01:00 30.16%
1/30/2016 3:14:00 3:50:00 45.75%
1/31/2016 2:51:00 6:19:00 31.09%
2/1/2016 2:05:00 5:28:00 27.59%
2/2/2016 2:11:00 4:01:00 35.22%

Conclusion.... No change at all! Well at least for me there is no change. 36% of my sleep is deep sleep (according to my trusted Garmin Fenix 3)

Sleep Data from the Garmin Fenix 3

From the Garmin Fenix 3 via your phone or their Garmin Connect online account you let the watch know your typical sleep times (most of us have some sort of routine) and the watch will record your sleep.

Sleep Movement Garmin Fenix 3

The graph above is the movement during sleep. Garmin will interpret this data into deep and light sleep and that looks like the following.

Garmin Fenix 3 Light and Deep Sleep Comparison

Typically activity trackers that monitor your sleep will flag up just how little sleep you have. Read up on sleep and how much you should get. Then you will realise it is important and the deep sleep is what counts. In the chart above deep sleep is represented by the dark navy bars and the light sleep the light blue. Pink is awake time.

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