Alcohol vs resting heart rate during sleep

On 6 nights after I drank, my resting heart rate was about 2.5 beats per minute faster while I slept than on 6 nights I didn't. I recorded and analyzed the data on the SquareOne app. Results were strong on a permutation test: out of 36 possible head-to-head pairings of a drinking night against a sober night, the drinking night came out higher more than 90% of the time.

Introduction

I had seen my Oura ring "readiness" score go down after even one glass of wine at dinner the previous night. That score is calculated using resting heart rate as one of the inputs, so I hypothesized that measuring RHR directly would show an effect. I ran the prospective experiment on RHR, with randomization, to see whether alcohol causally affects RHR and this is not just a spurious correlation.

Methods

For 14 days, an algorithm assigned each day as "on" (1–2 drinks) or "off" (no alcohol) and I typically had a glass of wine or an ounce of whiskey. Some nights I had a whiskey and a glass of beer.

The order of days was randomly shuffled rather than strictly alternating:

• On: days 1, 4, 5, 7, 10, 12, 14
• Off: days 2, 3, 6, 8, 9, 11, 13

My Oura ring recorded resting heart rate overnight, and each night's reading was credited to the day before it. I didn't log exact drink sizes or timing.

The analysis came from SquareOne's statistics service: mean difference between arms, a bootstrap confidence interval (5,000 resamples), a permutation test that shuffles the on/off labels 10,000 times to see how often chance alone produces a gap this big, and a standard t-test.

Results

Difference: +2.5 bpm on drinking nights (95% CI 1.1 to 3.8). The interval stays well clear of zero.

How likely is this by chance? Shuffling the labels produced a gap this large about 2% of the time (permutation p = 0.02). The t-test agrees (t = 3.4, p = 0.007).

Effect size: Cohen's d of about 2. That's big, mostly because my sleeping heart rate is very steady night to night, so a 2.5 bpm bump stands out clearly against the noise.

Adherence: I went off-plan on day 9 (had a drink on an "off" day instead of abstaining), and forgot to wear my ring on one of the "on" days, leaving six nights in each arm. So 13 of 14 days completed as assigned (93%) but we have 12 effectiv