Sleep Extension: Are More Sleep Hours Always Better?

We’ve all heard that sleep is vital for our well-being, but can you get too much sleep? And can too much sleep lead to negative health effects?

Conventional wisdom might suggest that the more sleep we get, the better we feel. But this isn’t what most large population studies of sleep duration find.

Long sleep durations are often associated with the worst health outcomes (e.g. Kripke et al., 2002). The problem is, these studies are not clear on whether the long sleep is a cause of the poor health, or whether poor health causes the long sleep.

So could it be that more sleep and time in bed actually leads to negative heealth outcomes?

Well, that’s the intriguing findings of a pilot study that explored this question.

The Myth of "More Sleep is Better"

Before we jump into the nitty-gritty of the study, let's address a common belief: the idea that more sleep is always better.

While it's true that not getting enough sleep (less than 6 hours) is associated with increasing health risks, getting too much sleep (8.5 hours or more) isn't necessarily a ticket to better health either.

In fact, studies have consistently found a U-shaped relationship between sleep duration and mortality - suggesting that both ends of the spectrum, too short and too long, can be problematic for your health and wellbeing (Kripke et al., 2002; Patel et al., 2004).

But why is long sleep associated with poor health? Could it be poor health triggering long sleep?

A Closer Look at the Sleep Extension Study

In an effort to shed light on this topic, Reynold et al. (2014) conducted a pilot study to investigate the effects of extending time in bed (TIB) on various health parameters.

The study was designed as a randomized controlled trial, involving 14 healthy adults (10 females, mean age 31.79±10.94 years). Participants had to be between 18-55 years old, report average sleep durations of 6-9 hours, and have no sleep complaints. Key exclusion criteria included shift work, significant health issues, and obesity (BMI >30).

The study protocol included a one-week baseline period followed by randomization into two groups:
- one group experiencing a TIB extension (adding 3 hours to their baseline sleep) and
- another group maintaining their usual sleep schedule.

Data collection involved wrist actigraphy, sleep diaries, mood assessments, inflammation markers and other physical parameters.

The Surprising Effects of Extended Sleep

So, what happened when participants spent extra time in bed?

The results are surprising.

Participants in the TIB extension group saw an increase in total sleep time by approximately 120 minutes.

However, this did not translate to a better mood or improved health outcomes. On the contrary, the extension group reported:

1. Increased Depression Levels: Participants who spent more time in bed showed increased depression scores, with the effect being five times stronger than in the control group.

2. Increased Anxiety Levels: Anxiety scores rose in the sleep extension group, leading to a 1.5x effect size difference to those maintaining their normal schedule.

3. Increased Inflammation Response: Perhaps most striking was the discovery that a key marker of inflammation (Interleukin-6) doubled in participants extending their sleep. This finding aligns with previous research by Patel et al. (2009) showing connections between long sleep duration and increased inflammation.

4. Decreased Sleep Quality: Despite spending more time in bed, participants reported feeling sleepier and experienced worse overall sleep quality. This suggests that more time in bed doesn't necessarily translate to feeling more rested.

Interestingly, participants in the TIB extension group struggled to meet the 3hrs extra time in bed and instead only managed around 2hrs 7mins.

Health Connections: The Bigger Picture

These findings add to a growing body of evidence linking excessive sleep with various health concerns.

Previous research has connected long sleep duration to:

• Increased risk of depression (Patel et al., 2006)

• Cognitive problems (Ferrie et al., 2011)

• Higher rates of cardiovascular disease and diabetes (Ayas et al., 2003)

• Greater risk of obesity (Taheri et al., 2004)

Why Extended Sleep Might Be Harmful

But why does spending more time in bed have such negative effects?

The study suggests several possible mechanisms.

• First, increased TIB often leads to more sedentary behavior, which has its own health risks (Ford et al., 2005) (although the authors of the study noted that the extension group actually increased exercise relative to the control group).

• Second, long sleep durations can result in reduced physical activity levels during the day, potentially leading to lethargy and decreased energy (Patel et al., 2012) contributing to the poorer mental health.

• Third, extending TIB can cause sleep fragmentation, which negatively impacts sleep quality, bodily inflammation, and overall health (Benkirane et al., 2022; Patel et al., 2009)

Practical Implications: Focusing On Sleep Quality And Finding Your Optimal Sleep Duration

This study challenges the assumption that extending sleep duration is universally beneficial and highlights the importance of personalized sleep recommendations.

But the takeaway from this study is not that more sleep is bad per se, instead it’s that there is likely to be an optimal sleep duration for each individual.

For better health, instead of simply trying to sleep longer, it may be more beneficial to focus on the quality of sleep and finding a personal sweet spot for sleep duration (think of it like your personal sleep “Goldilocks” zone - not too long, not too short, just right). For most people over 30 years of age, this should be no more than 7.5hrs -8hrs time in bed. Younger adults in their 20s may be between 8-9hrs.

Limitations and Future Directions

It's important to note that this study had its limitations, including a small sample size that limited the ability to detect statistically significant effects, and the extreme degree of TIB extension that participants struggled to maintain. Also, it wasn’t possible to separate the effects of increased sleep and increased time in bed so it isn’t clear if either or both could contribute to the effects. The researchers suggest that future studies should involve larger samples and more moderate sleep extension protocols and varying time in bed without extending sleep, to verify these findings.

Clinical Comment: Rethinking How We Think About Sleep

The study by Reynold et al. (2014) provides valuable insights into the effects of sleep extension, challenging the notion that more sleep is always better.

In the clinic we are always having to point out to people that sleep quality and consistency is more important than sheer quantity and that excessive sleep can have its downsides.

In particular, this study is especially important for those experiencing sleep problems as in our clinical experience, the first thing they do is extend their time in bed in the hope they’ll get more sleep. Yet this study suggests that this strategy may actually create more problems in terms of feeling worse, and could actually fragment sleep more, perpetuating the sleep problems further.

The study was published in the Journal of Sleep Research, (Reynold et al., 2014)

References

Ayas, N. T., White, D. P., Al-Delaimy, W. K., Manson, J. E., Stampfer, M. J., Speizer, F. E., & Hu, F. B. (2003). A prospective study of self-reported sleep duration and incident diabetes in women. Diabetes Care, 26(2), 380-384.

Benkirane, O., Delwiche, B., Mairesse, O., & Peigneux, P. (2022). Impact of sleep fragmentation on cognition and fatigue. International Journal of Environmental Research and Public Health, 19(23), 15485.

Ferrie, J. E., Shipley, M. J., Akbaraly, T. N., Marmot, M. G., Kivimäki, M., & Singh-Manoux, A. (2011). Change in sleep duration and cognitive function: findings from the Whitehall II Study. Sleep, 34(5), 565-573.

Ford, D. E., & Kamerow, D. B. (2005). Epidemiologic study of sleep disturbances and psychiatric disorders: An opportunity for prevention? JAMA, 262(11), 1479-1484. https://doi.org/10.1001/jama.262.11.1479

Kripke, D. F., Garfinkel, L., Wingard, D. L., Klauber, M. R., & Marler, M. R. (2002). Mortality associated with sleep duration and insomnia. Archives of General Psychiatry, 59(2), 131-136. https://doi.org/10.1001/archpsyc.59.2.131

Patel, S. R., Malhotra, A., Gottlieb, D. J., White, D. P., & Hu, F. B. (2006). Correlates of long sleep duration. Sleep, 29(7), 881-889. https://doi.org/10.1093/sleep/29.7.881

Patel, S. R., Zhu, X., Storfer-Isser, A., Mehra, R., Jenny, N. S., Tracy, R., & Redline, S. (2009). Sleep duration and biomarkers of inflammation. Sleep, 32(2), 200-204. https://doi.org/10.1093/sleep/32.2.200

Reynold, A. M., Bowles, E. R., Saxena, A., Fayad, R., & Youngstedt, S. D. (2014). Negative effects of time in bed extension: A pilot study. Journal of Sleep Research, 23(6), 657-666. https://doi.org/10.1111/jsr.12172

Taheri, S., Lin, L., Austin, D., Young, T., & Mignot, E. (2004). Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Medicine, 1(3), e62. https://doi.org/10.1371/journal.pmed.0010062