🛌 Just one week of poor sleep can decrease testosterone by 15%

The majority of the daily testosterone release in men occurs during sleep. In older men especially, morning testosterone levels are closely linked to total sleep duration.

It’s already well-established that sleep fragmentation and obstructive sleep apnoea can lower testosterone.

But new research has revealed something even more striking: after just one week of a slightly altered sleep routine (reducing total sleep time from 8 to 5 hours), testosterone levels in healthy male volunteers dropped by 15%.

This decline was most noticeable between 2 p.m. and 10 p.m., a time when energy and focus are typically needed most.

To put this into perspective, normal aging causes testosterone to decline by about 1–2% per year. That means this one-week drop is equivalent to 10–15 years of natural aging.

Interestingly, no changes were observed in stress hormone levels. However, symptoms of low testosterone—such as fatigue, reduced libido, poor concentration, and increased sleepiness—can all be triggered by sleep deprivation alone.

🥊 Summary

While the occasional bad night is inevitable, consistently prioritising sleep is essential. Sleep isn’t a luxury, but a biological necessity for maintaining healthy testosterone levels.

☕ How does caffeine affect the brain during sleep?

We all know caffeine helps us stay awake. But what happens when it’s still in your system after you fall asleep?

A recent study using AI and EEG (electroencephalography) explored how caffeine affects the brain during sleep. Forty adults took caffeine capsules three hours and then one hour before bedtime. The results were eye-opening.

Caffeine increased the complexity of brain signals during sleep, especially during the non-REM (NREM) phase, which is crucial for memory consolidation and cognitive recovery. In simple terms, caffeine keeps the brain in a more alert, reactive state, even while asleep.

While this heightened brain activity is helpful during the day, it can interfere with the brain’s ability to fully relax and recover at night. This disruption may explain why caffeine can impair memory processing and reduce the quality of rest.

Interestingly, younger adults (ages 20–27) showed a stronger response to caffeine. This is likely due to their higher density of adenosine receptors: the molecules that build up during the day to promote sleepiness. As we age, these receptors decline, which may explain why caffeine has a milder effect on older individuals.

🥊 Summary

In short, caffeine shifts the brain toward wakefulness, even during deep sleep, and younger brains may be more vulnerable to its effects.

🏃‍♂️Sleep loss = performance loss. How missing sleep impacts your game

It’s no surprise that sleep deprivation affects athletic performance. But just how much?

A recent study explored the short-term effects of different types of sleep deprivation on exercise performance and perceived fatigue in athletes and healthy non-athletes aged 15–40. The sleep conditions included:

• Total sleep deprivation: No sleep for 24+ hours

• Partial deprivation – Early wake: Waking ~3 hours earlier than usual (e.g., 3:00 AM)

• Partial deprivation – Late bedtime: Delaying sleep by ~3–4 hours (e.g., going to bed at 3:00 AM)

Compared to a normal 7–9 hour sleep routine, all forms of sleep loss led to measurable declines:

• Skill-based movements: Accuracy dropped by 20–30%, especially after late bedtimes

• Endurance: Significantly reduced—non-athletes lost the equivalent of 1–2 miles of running capacity after just one sleepless night

• Explosive power: Fell by 5–10%, particularly with early wake-ups

• Speed: Slowed down most when sleep was cut short in the morning

• Strength: Dropped by 3–5%, again worse with early wake-ups

• Perceived effort: Workouts felt twice as hard, especially in the afternoon and after partial sleep loss

Both total and partial sleep deprivation, especially waking too early, can meaningfully impair performance, particularly during afternoon sessions when fatigue and circadian dips hit hardest.

🥊 Summary

While the study had limitations (short-term protocols, lab settings, and underrepresentation of females), the message is clear: sleep is a performance enhancer you can’t afford to skip.