The T1D Sleep-Blood Sugar Feedback Loop
Bad sleep makes your blood sugar harder to manage. Worse blood sugar disrupts your sleep. Worse sleep makes your blood sugar worse. You've been running a feedback loop, without knowing it. This is the episode where things click. Neil...
The episode, word for word
I have some slightly annoying news.
The thing you thought mattered the most about sleep? The number of hours?
It's not the number.
Or, more accurately, it's not JUST the number. The number matters. But it's not the whole story. The part that matters more is something you've probably been ignoring entirely.
My name is Neil Greathouse, and this is Your Best T1D Year.
All right. I want to start with a study. 2023. Seventy-six adults with type 1 diabetes. Researchers had them wear a CGM and a sleep tracker simultaneously for one week. And then they looked at the relationship between sleep and time in range.
Here's what they found.
Sleep duration, total hours of sleep, was not independently associated with time in range.
I know. I'll give you a second.
So the thing we've been told forever, get your eight hours, get eight hours, eight hours is the number, eight hours, that's the goal, it turns out that in T1D specifically, hours alone don't tell the whole story. Six people who each got seven hours of sleep got seven very different results, depending on something else entirely.
OK. So what was actually associated with time in range?
Bedtime consistency.
Not duration. Timing.
Every extra hour of variability in bedtime, meaning the difference between when you went to bed on your best night versus your latest night, was associated with roughly ten percent less time in range. Ten percent. Per hour of variability.
Let me make that specific. If you go to bed at 10pm on Monday, 11pm on Tuesday, 10:30 on Wednesday, and 1am on Thursday... your CGM noticed. It was taking notes. It had opinions. It kept them to itself until your A1C appointment but it absolutely noticed.
You know how Michael Jordan, when he would describe a game where someone had a good game against him, would just quietly file it away? He'd be interviewed afterward, completely calm, very measured, and somewhere behind his eyes there was a locked room full of receipts? That's your CGM. That's literally what your CGM is doing with your inconsistent bedtimes.
Your CGM does not know it's Saturday. Your body does not know it's Saturday. Your cortisol does not know it's Saturday. Your insulin sensitivity does not know it's Saturday. Only your social calendar knows it's Saturday, and your social calendar is not in charge of your A1C.
OK. So this is either very validating or very annoying, depending on your situation.
If you've been sleeping the "right" number of hours but your overnight numbers still feel off, this might be why. It's not just how much you sleep. It's when.
And before I get to the challenge: I am not telling you to never stay up late. I am not telling you that one late night is going to tank your time in range. I'm telling you that consistent bedtimes are, according to the research, more associated with better glucose management than total hours. Which means if I had to give you one thing to work on, just one, it's going to bed within about an hour of the same time each night, including weekends.
I know. I know. Weekends. We'll talk.
For now: the data is the data. Same time, seven nights a week, is more valuable than eight hours at scattered times.
What time did you go to bed last night? The night before? Were they within an hour of each other?
This week, I want you to try to get within a sixty-minute window of the same bedtime, three nights in a row. Not all seven. Three. Pick the three nights that are most realistic for you.
Write the times down. That's it.
I want to say something to the person who's been genuinely trying. Getting the hours. Doing the thing. And still not seeing what they expected.
You weren't missing effort. You were missing information.
Same time. Same window. That's the piece.
You're not doing a bad job. You're doing a difficult job and you keep showing up anyway. That matters. I'm proud of you.
Type 1 diabetes is relentless, but managing it doesn't have to be. New episodes every Monday, Wednesday, and Friday. You're not doing a bad job, you're doing a difficult job. Nobody remembers easy.
This is the script as read on the mic, lightly tidied for reading. Education, not medical advice. Talk to your care team before you change anything about your insulin.