Study Summary
Sleep quality plays a crucial role in mental clarity and decision-making, particularly in high-demand professions such as financial trading. This study examined how daily alcohol and caffeine consumption, alone and in combination, affects sleep in a real-world sample of traders.
What They Did
Over six weeks, Song and Walker tracked 17 financial traders using daily digital surveys. Participants reported their intake of alcohol and caffeine, along with measures of sleep duration, quality, and number of night-time awakenings. The researchers analysed over 550 survey responses to identify patterns of sleep disturbance linked to these substances.
What They Found
Alcohol intake was associated with a measurable decline in subjective sleep quality, reducing it by an average of 3 points per glass on a 100-point scale. Although it did not reduce total sleep time, alcohol consumption tended to increase night-time awakenings and disrupt sleep continuity.
Caffeine had a different profile. It significantly reduced sleep duration, with each cup linked to about 10 minutes less sleep. However, it did not significantly affect how well participants felt they had slept, indicating a potential mismatch between actual and perceived sleep quality.
Surprisingly, when both substances were consumed on the same day, alcohol appeared to partially mask the negative effect of caffeine on sleep quantity. This suggests a compensatory pattern, where individuals may use alcohol in the evening to counteract the stimulating effects of caffeine taken earlier in the day.
Why It Matters
These findings provide ecological evidence that both alcohol and caffeine impair sleep in different ways, and that their combined use may obscure the user’s perception of poor sleep. This pattern could explain why professionals often use both substances in a cycle that undermines recovery, alertness, and long-term health.
My Clinical Insight
For professionals with high cognitive demands, such as traders, even low to moderate alcohol or caffeine use can interfere with restorative sleep. Alcohol may feel sedating, but its rebound effects disrupt sleep structure. Caffeine may reduce sleep time without making users feel more tired, creating a deceptive sense of resilience. Clinicians should help clients recognise these patterns and support behavioural changes that prioritise true sleep restoration.
Until sleep feels natural again, Dr Noaman
Reference:
Song F, Walker MP. (2023). Sleep, alcohol, and caffeine in financial traders. PLOS ONE,
