Article - The effects of time-restricted eating on sleep, cognitive decline, and Alzheimer's disease.

Expert Review

Reviewer: Kirsty Baxter

10th Mar 2023

Conflict of interest

None

Take home message

To highlight the potential benefits of time-restricted eating (TRE) as a potential preventative approach to delay the onset and progression of neurodegenerative disease such as AD

Evidence category

C: Non-randomized trials, observational studies, narrative reviews

Summary review

The authors highlight Alzheimer's disease (AD) is the most prevalent neurodegenerative disease affecting over 50 million aging people worldwide. While no cure is known for AD, this review proposes lifestyle interventions such as time-restricted eating (TRE) as a potential approach to delay the onset and progression of a neurodegenerative disease and could hint at autophagic mechanisms
TRE involves strategically limiting the eating window to 8- to 12-h with fasting—drinking only water and calorie-free coffee/tea—for 12 to 16 h within a 24-h cycle.

Objectives

To investigate the effects of TRE on sleep and cognitive decline in healthy individuals

Results

Nine RCTs with varied length between one and sixteen weeks were examined
A 5-week randomised controlled trial (RCT) showed no significant change in sleep quality between early TRE (fasting between 6 a.m.–3 p.m.), mid-day TRE (11 a.m.–8 p. m.) and control (ad lib intake) in 82 healthy subjects without obesity but the sleep quality improvement was greater in early TRE group (PSQI:Δ=−1.08±1.78vs.Δ=−0.22±2.19andΔ=−0.36±1.73, respectively).
Sleep quality using the myCircadianClock app reported significant improvement in sleep quality (23 %) following a 12-week single arm intervention of 10-h TRE.
Following a 16-week TRE intervention sleep duration was reported to be improved from a subjective score of 6 at base line to 8 after 36 weeks in eight overweight and obese subjects; however, the study used a subjective self-assessment survey for measuring sleep duration.
The Pittsburgh Sleep Quality Index (PSQI) was carried out to assess sleep quality and disturbances in six trials but no trial reported significant improvement in sleep quality using the PSQI survey with TRE

Conclusion

Authors highlight TRE as promising for its potential to reduce the markers of aging and neurodegenerative disease.

Clinical practice applications

To inform practitioners of the potential benefits of TRE that involves limiting the eating window to 8- to 12-h with fasting—drinking only water and calorie-free coffee/tea—for 12 to 16 h within a 24-h cycle.
TRE may improve regulation of circadian rhythm and autophagy through aligning food intake with circadian rhythm, which coordinates metabolism and physiological functions including glucose, insulin sensitivity, lipid levels, energy expenditure, inflammation, sleep and cognitive function.
TRE activates a metabolic switch which occurs 12–36 h after fasting is initiated and free fatty acids are released into the blood.
TRE improved sleep quality and sleep duration, where a longer fasting period in TRE approach (≥12 h fasting) was associated with significantly higher sleep duration.

Considerations for future research

The potential benefits of TRE in neurodegenerative diseases such as AD should be further investigated clinically.
The optimal time to initiate fasting needs to be identified in future trials.
The potential benefits of TRE in neurodegenerative diseases such as AD in the context of sleep should be further investigated.

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Abstract

According to the United Nations, by 2050, one in six individuals will be over age 65 globally, and one in four people would be aged 65 and older in western countries. The unprecedented growth of the aging population is associated with increased age-related disorders like Alzheimer's disease (AD) and Mild cognitive impairment (MCI). To date, no cure is known for AD, thus lifestyle interventions including calorie restriction (CR) and time-restricted eating (TRE) are proposed as potential approach to delay the onset and progression of the disease. Sleep disturbances are common in people with MCI and AD. Moreover, accumulating data indicates that pro-inflammatory cytokines including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-10 increase in individuals with AD and MCI versus healthy subjects. Thus, the purpose of the present review is to describe the potential effects of TRE on sleep, cognition decline, and neuroinflammatory markers in humans. Preliminary evidence suggests that TRE may produce neuroprotective effects on cognition and reduce neuroinflammatory markers related to AD in humans. To date, no studies investigated the effects of TRE on sleep disturbances and patients with AD. Thereby, the impact of TRE on cognition in individuals with cognitive decline and AD needs to be investigated further in randomized controlled trials (RCTs).

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