Sleep optimization

What sleep optimisation can achieve

Sleep optimisation is not a standardised protocol with guaranteed results. A sensible approach is to consider the amount and regularity of sleep first, and then to address identified disruptive factors such as caffeine, alcohol, light and specific aids.

Amount and regularity of sleep

For healthy adults, there is a joint recommendation from the American Academy of Sleep Medicine and the Sleep Research Society regarding the amount of sleep required. It is based on a modified RAND consensus procedure and is therefore an expert recommendation, not a direct intervention study. A general target range of 7 to 9 hours is therefore not supported by evidence.

A literature review involving a formal expert consensus assessed 63 full-text publications. The panel concluded that consistent times for falling asleep and waking up are important for health, safety and performance. No universal time or permissible range of variation was specified.

The consensus paper considers catching up on sleep at weekends or on days off following insufficient sleep during the week to be potentially beneficial. Regularity is therefore a guideline, but not a rigid rule without context. It does not follow from this that catching up on sleep reverses all the consequences of reduced sleep, nor is there an optimal duration for catching up on sleep.

Which disruptive factors were directly investigated

Caffeine: Consider both the timing and the dose

In a randomised, placebo-controlled trial, 400 mg of caffeine disrupted sleep when taken at bedtime and 3 or 6 hours beforehand. Sleep disturbance was greater than with placebo at all three time points, in each case with p < 0.05. The authors considered the reduction in total sleep time following intake 6 hours before bedtime to be significant.

Only a single fixed dose was investigated. The study did not examine either a dose-response relationship or individual caffeine metabolism. It therefore does not provide evidence for either a general half-life of 5 to 6 hours or a universal 8-hour exclusion window.

Alcohol: falling asleep more quickly is no indication of better sleep

A systematic review and meta-analysis of 27 studies involving healthy adults found dose-dependent changes in sleep architecture. Even at doses as low as approximately 0.50 g/kg, alcohol delayed the onset of REM sleep – a phase of sleep characterised by rapid eye movements – and shortened its duration. The effect on REM sleep increased with rising doses. At high doses of 0.85 g/kg and above, the latency to sleep and the latency to reach N3 – the deepest stage of non-REM sleep – were shortened. No clear effect could be determined for total sleep time, sleep efficiency or wake time after falling asleep.

A shorter sleep latency is therefore not evidence of better or more restful sleep. The findings describe acute, dose-dependent effects under varied conditions and do not support a blanket assertion that alcohol generally disrupts deep sleep and REM sleep.

Light and the sleeping environment

A meta-analysis of 12 studies on blue light filter interventions found a Hedges’ g value of 0.31 for sleep efficiency, with a 95 per cent confidence interval of –0.05 to 0.66, based on 7 studies. For total sleep time, the value was 0.32 with a 95% confidence interval of 0.01 to 0.63 based on 6 studies. For the self-reported Pittsburgh Sleep Quality Index, it was -1.25 with a 95% confidence interval of -2.39 to -0.11 across 3 studies. The confidence interval for sleep efficiency includes the zero value and does not support a clear overall effect. Hedges’ g is a standardised effect size. Higher sleep efficiency and longer total sleep time are favourable outcome measures, whilst a lower score on the Pittsburgh Sleep Quality Index is favourable. The three estimates should therefore not be interpreted as a single ranking.

Furthermore, filter glasses are not the same as spending less time in front of a screen, dimming the screen in the evening or being exposed to natural light in the morning. There is a lack of direct, controlled human-based evidence to support a fixed ‘1- to 2-hour rule’ for reducing screen time, exposure to natural daylight in the morning, a bedroom temperature of around 18 °C, as well as complete darkness and minimisation of noise.

Melatonin and other aids

A meta-analysis of 26 double-blind, randomised trials involving 1,689 participants examined people with insomnia and healthy volunteers. Melatonin reduced the time taken to fall asleep and increased total sleep time.

Dose-response modelling showed a gradual reduction in sleep latency and an increase in total sleep time, up to a model maximum at 4 mg per day. Taking the supplement approximately 3 hours before the desired bedtime was modelled as potentially beneficial. These values are model estimates and do not constitute general self-medication advice. Long-term safety and adverse effects have not been adequately assessed. There are no suitable human studies available for magnesium, L-theanine and glycine with clear sleep-related endpoints and sufficient safety data.

What can be deduced regarding recovery and strength training

A randomised crossover study involving 13 healthy young adults, comprising 7 men and 6 women, compared a night of complete sleep deprivation with a night of normal sleep. On the following day, there was no difference between the two conditions in the markers of muscle protein breakdown that were examined.

This is a mechanistic negative finding. It does not rule out other acute reactions and does not prove either the absence of all catabolic processes or chronic muscle loss. The study lasted one night, did not measure muscle mass or strength over a longer period, and did not involve a specific strength training population. Long-term effects on muscle mass, strength, training performance or recovery are therefore not demonstrated.

An evidence-based sequence for clinical practice

1. First, check how much sleep you are getting and how regular your sleep pattern is: There is no evidence to support a specific average number of hours; similar times for going to bed and getting up provide a reasonable guide. If you have not had enough sleep, catching up on sleep on days off can be helpful.
2. Assess caffeine intake based on dose and timing: Even 400 mg can disrupt sleep if taken as late as 6 hours before going to bed. This does not imply a general half-life or exclusion window applicable to everyone.
3. Do not regard alcohol as a reliable aid to falling asleep: Faster onset of sleep may be associated with dose-dependent changes in sleep architecture.
4. Classify light filters and the environment as individual tests: The filter data is inconsistent. There is a lack of direct, isolated data on the effectiveness of specific rules relating to screen use, temperature, darkness and noise.
5. Treating melatonin on a case-by-case basis: The meta-analysis provides model estimates, but no general dosage guidelines and no adequate long-term assessment for strength athletes.
6. Do not equate acute sleep deprivation with chronic muscle loss: The finding of no significant changes in protein breakdown markers does not provide any answers regarding long-term training or body composition.

Limitations of the statement

The available research mainly involves healthy adults, heterogeneous populations or acute exposures. There is a lack of long-term studies on adults who undertake resistance training that directly link sleep optimisation to muscle mass, strength, training performance or recovery. Furthermore, chronotype, baseline sleep, age, gender, energy availability, caffeine metabolism, training intensity and individual response have only been partially investigated. Sleep optimisation can therefore be understood as a limited, context-dependent practice, rather than a precise, universal checklist.

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