How a Nightcap Can Turn Snoring Into Something Worse

This early but influential study tested something directly rather than inferring it statistically: what happens to a person's breathing overnight if they drink beforehand? Seven patients, ranging from habitual snorers to those with diagnosed obstructive sleep apnoea, underwent overnight breathing studies both with and without alcohol beforehand. In the five patients who already had sleep apnoea, alcohol increased both the frequency and duration of breathing obstructions and worsened the drop in blood oxygen during the first hour of sleep. More strikingly, in two patients who were only chronic snorers with no prior apnoea, alcohol was enough to trigger genuine obstructive sleep apnoea that night.

The sample is tiny by modern standards, seven people, and the study is decades old, so it can't speak to how this varies by sex, age or degree of drinking. What it offers that population-level statistics can't is direct, same-night cause and effect: this wasn't just correlation, it was alcohol visibly worsening one person's breathing on the very night they drank it, which is exactly the mechanism the larger, more recent meta-analyses go on to confirm at scale.