> ## Content Index
> Fetch the complete content index at: https://www.autodidacts.io/llms.txt
> Use this file to discover other available public pages before exploring further.

# An unsolved question in sleep science
- URL: https://www.autodidacts.io/long-sleep-duration-and-mortality/
- Published: 2026-01-02T21:21:28.000Z
- Updated: 2026-01-03T01:49:20.000Z
- Description: Or, a display of my ignorance of sleep science
- Author: Curiositry
- Tags: 100DaysToOffload, Science, Sleep, Longevity

****Note:** this post is part of [#100DaysToOffload](https://100daystooffload.com/?ref=autodidacts.io), a challenge to publish 100 posts in 365 days. These posts are generally shorter and less polished than our normal posts; expect typos and unfiltered thoughts! [View more posts in this series.](https://www.autodidacts.io/tag/100daystooffload/)

  
After reading *Why We Sleep* by Matthew Walker, and Alexey Guzey’s essay *Matthew Walker’s “Why We Sleep” Is Riddled with Scientific and Factual Errors,* and feeling drawn to join in the fray with an essay titled, gloriously, *Alexey Guzey’s ‘Matthew Walker’s “Why We Sleep” Is Riddled with Scientific and Factual Errors’ Is Riddled with Scientific and Factual Errors* (except that it’s not), one debate still plagues the dinner table:

**Is it unhealthy to get *too much* sleep?** Presumably, *too much* would be 9hrs+, since many sources recommend 7–9hrs sleep for optimal health.

There are graphs showing *correlation* between long sleep and poor health:

![Sleep duration and all cause mortality](https://www.autodidacts.io/content/images/2025/12/sleep-duration-and-all-cause-mortality.jpg) 

Source: [https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.880276/full/](https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.880276/full/?ref=autodidacts.io)

And [this meta-analysis](https://pmc.ncbi.nlm.nih.gov/articles/PMC2864873/?ref=autodidacts.io) concludes **“Both short and long duration of sleep are significant predictors of death in prospective population studies.”**

(“Sleep duration was assessed by questionnaire and outcome through death certification.”)

But this could easily be confounding factors (sick people need more sleep).

I have never found an *interventional* sleep study of this topic, or one that finds *causation*.

Is this because:

1. **You can’t just tell healthy people to sleep for ten hours a night?** (Or, you can, but they won’t actually do it)?  
  - But maybe you could tell them to lie still and try to sleep, if you paid them well enough?
2. **It’s an ethics board thing:** nobody can do this study because if it *is* causation and not correlation, you would be hurting people by requiring them to oversleep.

If it’s the second, are there interventional studies of long sleep duration and all cause mortality in rats/mice? And would these generalize to humans?

I’d appreciate comments/emails from anyone who has found good research on this topic.