Middle Age Sleep Problems? 9 Common Changes To Expect

Having trouble sleeping in your 40s, 50s and beyond? In this article we cover the characterization of related changes in sleep structure on both the macro and micro scale, and the differences between men and women when it comes to sleep and age – yes, there’s a difference.

Sleep is incredibly important for the human body as a whole and on a cellular level. The causes of alterations in the quantity and quality of sleep, and the consequences of these changes, are paramount to understanding how sleep impacts our overall wellness. E.g.,

What changes exacerbate aging and a more dysfunctional physiology?

What changes are caused by aging that are detrimental to your health?

In this article we cover the characterization of related changes in sleep structure on both the macro and micro scale, and the differences between men and women when it comes to sleep and age -- yes, there’s a difference.

First, let’s start with a baseline understanding of our sleep cycles.

The Difference Between REM and NREM

As you sleep, you move through a cycle of REM and non-REM (NREM) phases. REM stands for rapid eye movement, and is our deepest phase of sleeping. In REM our eyelids may flutter and our breath patterns may change -- however, there is no visual information sent to the brain. The ultimate goal is to reach REM, our deepest level of sleep, at least four times during our sleep period.

But before we achieve REM, there’s NREM. Although it would be wonderful to fall into REM right when we lay down and close our eyes, we follow a three-phase process that makes up NREM sleep:

  • N1 -- occurs right after we fall asleep, and usually lasts ~10 minutes.

  • N2 -- occurs after N1, the phase where your muscles relax and you begin slow-wave brain activity (see figure B). This phase usually lasts ~30-60 minutes.

  • N3 -- occurs after N2, and is a deep sleep phase where delta brain activity increases. If you’ve ever experienced or felt a twitch before falling asleep, you were likely in N3. This phase usually lasts ~20-40 minutes, right before falling into REM.

Common Sleep Cycle Changes That Happen As We Age

When you age your quality and quantity of sleep changes, you yourself can attest to this.

Figure A

Referencing the above, you can see the comparison of a 9-hour sleep cycle between younger adults <50, and older adults >50. Compared to the younger sample size, older adults experience a much more fragmented sleep schedule with prolonged periods of awakeness during the middle of the night.

Once you're into your 50’s your sleep architecture goes through radical changes. These changes are not universal and each individual will present different changes in their sleep architecture, if any at all.

9 Sleep Changes You’re Likely To Experience As You Age:

  1. Advanced sleep timing - sleep occurs between 6 p.m. and 9 p.m. with waking between the hours of 2 a.m. and 5 a.m.
  2. Longer sleep-onset latency - the longer it takes for sleep to occur, the longer it will take to reach the first REM sleep stage
  3. Shorter overall sleep duration - the sleep that does occur, happens in shorter than usual time spans
  4. Increased sleep fragmentation - sleep fragmentation is the total number of awakenings and transition to stage 1 sleep divided by the total sleep time, or those brief moments of wakefulness that occur when you're sleeping
  5. More fragile sleep - sleep that is easily disrupted or waking up because of every little bump in the night
  6. Reduced amount of deeper NREM sleep - the reduction of sleep in which your body begins to relax
  7. **Increased time spent in lighter NREM Stages 1 and 2 **- while sleeping you will spend more time in NREM stages 1 and 2
  8. Shorter and fewer NREM-REM sleep cycles - while sleeping, you will only experience a few cycles between non-REM and REM, compared to the standard amount for a healthy human body.
  9. Increased time spent awake throughout the night - sleep that is constantly disrupted by the classic tossing and turning.

Macro Sleep Changes in Adults

Age-related reduction of time in REM sleep is often more so linked to changes within your NREM sleep cycles or as symptoms of degenerative dementia, an age-related disease.

Additionally, the increase in naps during the day also increases as you age, with 10% of adults aged 55-64, and 25% of adults aged 75-84, reporting daytime naps. With roughly half of these two groups' naps being unplanned, which is consistent with the claim that 1 in 4 of older adults report that daytime sleepiness impairs their daytime plans on a regular basis, these daytime abnormalities may reflect the sleep issues that affect older adults (Foley et al., 2007).

Excessive daytime sleepiness and naps are not universal for old age, with some adults reporting diminished or less daytime sleepiness as well (Dijk et al., 2010). The one factor that appears to control whether or not an adult will be prone to daytime sleepiness or naps is the <u>presence of multiple conditions such as chronic pain, depression, sleep disorders, and frequent urination during the night.</u> (Foley et al.,2007, Vitiello, 2009)

The propensity of daytime sleepiness can be higher in an otherwise healthy older
adult than a younger adult in the evening despite the circadian alerting signal being at its peak in young adults (Münch et al., 2005). Thus, the discrepancies between daytime sleepiness in older adults appears to partially depend on the time of day and/or circadian preference of the individual adults being compared.

This becomes further relevant given the advancement in circadian preference in older adults, wherein older adults shift to early bedtimes and early wake times. (Monk, 2005).

Micro Sleep Changes in Adults

In addition to larger macros sleep changes, there are just as significant changes within the
signature electrical oscillations of sleep. Signature electrical oscillations, which are measured with electroencephalography (EEG), are most prominent within NREM sleep and two of its fellow oscillations -- slow waves and sleep spindles-- which are the pattern of brain waves that occur during NREM sleep.

Figure B

One method of quantifying slow waves is through the measurement of spectral power in the 0.5-4.5 Hz range during NREMsleep or slow wave sleep, also known as slow wave activity (SWA).

SWA is tightly bound to the homeostatic drive to sleep following continued wakefulness -- the longer you're awake, the greater the pressure and desire to sleep is. Additionally, the amount of SWA will increase proportional to the time spent awake. Borbély, 1982.

Reductions in SWA are observed in middle-aged adults and become especially pervasive into our elder years.

It's important to note that age-related decreases in SWA are not evenly distributed with respect to head topography or sleep cycles throughout the night. Instead, maximal age-related decrements in absolute SWA are observed over the prefrontal cortex derivations and in the first NREM sleep cycles, with 75-80% reductions on average relative to young adults (Fig 1B).

For young adults, SWA is highest within the first NREM cycle of the night and then SWA decreases as the night progresses in successive NREM sleep cycles. This decrease in SWA reflects the homeostatic dissipation of sleep pressure as you sleep through the night; that is, the more tired you are, the more slow wave activity there will be. (Landolt and Borbély, 2001, Landolt et al., 1996).

Homeostatic Sleep Regulation Changes With Age

The process of homeostatic sleep regulation, including SWA, is also changed as a function of
aging. The exponential slope of SWA dissipation through the night is less in older adults when compared to those younger (Fig 2A). Landolt and Borbély, 2001 Landolt et al., 1996

Additionally, homeostatic increases in slow wave sleep time and SWA in response to staying awake to the point of sleep deprivation or selective slow wave sleep suppression are blunted within older adults compared to younger adults (Fig 2B).

Figure 2.jpeg

This finding has been interpreted as an impairment of the homeostatic regulation of SWA in older adults, with changes observed in the prefrontal cortex.

Underlying the changes in SWA is the expression of two NREM slow wave features -- the
amplitude of slow waves, and the density of slow waves, being significantly reduced within middle-aged adults. This reduction is further exacerbated as you age, with further reductions in amplitude and density. (Carrier et al., 2011, Dubé et al., 2015).

Note that these age-related fluctuations in amplitude and density are not uniform across the brain and that these age-related differences are more prevalent during the 1st and 2nd stages of NREM sleep cycles.

Additionally, the slope of the slow waves becomes increasingly shallower as you age. These changes suggest that aging may diminish and degrade the synchronized neuronal en masse firing that creates the sleep oscillations, via the disruption of the polarization needed to shape the slow waves (Beenhakker and Huguenard, 2009).

Another drastic change is the reduction of slow wave frequency to roughly 0.1 Hz in older adults. This reduction in frequency can also be observed throughout the brain as opposed to the area specific changes of amplitude and density.

Surprisingly, the reduction of slow wave frequency is not found within older adults with Beta-amyloid (Aβ) burden and adults with poor memory retention. This link possibly gives credence to using slow wave frequency as a new sleep biomarker in distinguishing normal aging versus abnormal aging within the context of Alzheimer's disease pathophysiology. Mander et al., 2016a, Carrier et al., 2011.

Sleep Spindle Regulation Changes As We Age

The sleep spindle, another definer of NREM sleep oscillation, goes through its own changes during your later life. The sleep spindles reflect the transient bursts of oscillatory activity in the 12-15 Hz range and are generated via corticothalamic networks interacting with the reticular nucleus of the thalamus.

Unsurprisingly, sleep spindle frequency is reduced in middle-aged and older adults when compared to young adults. This further increases throughout the night, with the largest age-related impairments being observed up to 50% in the final sleep cycles of the night, as opposed to the faster frequency spindles which are more predominant in young adults. (Carrier et al., 2011, De Gennaro and Ferrara, 2003, Mander et al., 2014, Martin et al., 2013, Steriade et al., 1987, Dijk et al., 1989, Landolt et al., 1996).

There are three age-related disruptions in sleep spindles that affect older adults.

  1. Reduction in spectral power in the frequency range of sleep spindles generated with the number of sleep spindles declines significantly as you age into your later years.
  2. Secondly, the unique features of the spindle waveform are similarly affected as we age and appears to contribute to the overall reduction in the signal power that's connected to sleep spindles-- decrease in the duration, peak, and mean amplitude when you compare older adults to younger adults.
  3. Lastly, while the previous changes are temporally specific to different regions of the brain throughout the night, there is maximal impairments in spindle density and amplitude that are occurring over your frontal lobe when you compare an older adults to a younger. (Fig 1B). De Gennaro and Ferrara, 2003, Mander et al., 2014, Martin et al., 2013.

It's also good to note that age-related reductions in sleep spindles can be readily seen even when the sleep stage in which they wake up doesn't have any changes itself.

A good example would be when your stage 2 NREM sleep doesn't change in duration, but the sleep spindles within stage 2 NREM are reduced. Additionally, make note that the characteristic reduction in total NREM sleep is directly related with the selective loss of stages 3 and 4 of NREM sleep.

Thus, even when older adults get the same amount of NREM sleep time, important differences in the density and frequency of SWA can be seen. Therefore, the measurement of NREM sleep stage duration alone cannot capture all of the information with regards to the age-related differences in slow wave expression (De Gennaro and Ferrara, 2003, Fogel et al., 2016, 2016b, Martin et al., 2013, Feinberg and Carlson, 1968, Carrier et al., 2011, Dubé et al., 2015).

These findings provide evidence for a model in which age-related changes in macro-levels
sleep architecture can, and are more often than not, mechanistically distinct from the micro-level changes in sleep oscillations.

The Role of Gender on Aging and Sleep Patterns

While the differences between younger and older adult sleep changes is reliably distinct, the degree in which these older adults suffer sleep disruption varied wildly.

This large inter-individual variability means that age is not the sole determining factor of sleep disruption in older adults. Other factors that interact with the aging process must then determine whether older adults will suffer from age-related decline in both sleep quantity and quality.

Gender has a huge factor on your physiological functions throughout your life. It is a key factor that determines levels of sleep disruption with older men suffering from a greater disruption in NREM sleep when compared to women of the same age.

A comprehensive study further demonstrates that increasing age is reliably associated with the same detrimental effects previously described:

  • Decreased slow wave time
  • Reduced sleep efficiency
  • Increased NREM stage 1 sleep time
  • Increased times of waking up during the middle of the night
  • Decreased in REM sleep time

Figure 3.jpeg

Men over the age of 70 have a 50% reduction in their slow wave sleep compared to men under the age of 55, while still having an increase in NREM stages 1 and 2.

In women, there are no significant reductions in slow wave sleep nor increases in NREM sleep times when you compare older and younger demographics.

Comparatively, men over the age of 70 have more than a 3-fold deficit in slow wave sleep time compared with women of the same age group.

Further meta-analyses have also shown gender-specific differences in slow wave sleep time in older aged adults. While seemingly subject to differences in slow wave sleep time, both men and women showed moderate reductions in REM sleep time, suggesting a gender-independent deterioration of this sleep stage (Redline et al., 2004, Ohayon et al., 2004).

NREM changes are what we should be mindful of.

Sleep Deprivation & Aging

Gender also causes age-associated changes in slow wave sleep homeostasis, with older men
showing significantly less homeostatic slow wave sleep rebound during recovery sleep following sleep deprivation than women of the same age.

When you compare basic sleep stages, both older men and women show very similar homeostatic rebounds in REM sleep during post-deprivation nights. Thus gender-dependent and gender-independent effects emerge in older age, which further suggests that some homeostatic mechanisms remain functionally equivalent in both older men and women, like REM sleep, and some are shown to be strongly gender-dependent, like slow wave sleep. (Reynolds et al., 1986)

Now, when or what age this stratifying gender-dependent effect takes hold is still unclear, with both men and women in their 20’s showing no signs of NREM sleep differences.

Although, there is evidence that points to these differences emerging in your mid-30’s with the measurement of SWA.

Men in their mid-30’s have been shown to have a divergence which can be seen in the EEG spectral measure of SWA, which is roughly 50% lower in men in their mid-30’s when compared to their 20’s. The same comparison in women is shown to be only about 25% lower in women in their mid-30’s when compared to their 20’s. Further evidence on if and when these gender-dependent changes occur is sparse and lacking. (Ehlers and Kupfer, 1997, Van Cauter et al., 2000).

Sleep is incredibly important. We spend a large portion of our lives sleeping and understanding the biological impacts on both a macro and micro level is pivotal in further improving your health and expected shifts in sleep behavior as you age.

Furthermore, it's been shown that gender does play a role in determining your level of sleep disruption as you age. So the next time you’re tossing and turning in bed while your partner is sound asleep, maybe you’ll point back to this data and realize... ah, the perks of our aging experience!

With this evidence it's clear to see that how you sleep is how you age.

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