Contributed by Elias Malek, PhD
The effects of alcohol have become a hot topic lately, as we are starting to understand better and recognize just how much it disrupts sleep. However, most studies treat all types of alcohol (beer, wine, liquor, etc) under one umbrella, simply comparing “drinking nights” to “non-drinking nights.” That leaves an important question unanswered: does drinking different types of alcohol affect sleep and cardiovascular recovery differently? Our insights reveal that all types of alcoholic drinks harm cardiovascular recovery compared to no drinks, although some cause slightly more harm than others.
To understand the impact of the type of alcohol on sleep and cardiovascular recovery, over 170 Eight Sleep members completed daily surveys about whether they drank the previous night, and if so, what type of alcohol they drank and how much. We then linked their survey data to their Pod’s sleep and cardiovascular recovery metrics (e.g., heart rate and heart rate variability). We analyzed over 2,600 nights and found surprising insights about which types of alcohol impact overnight recovery the most.
Key Takeaways
- All alcohol types (compared to non-drinking nights) placed measurable strain on the heart by raising sleeping heart rate (HR) and lowering sleeping heart rate variability (HRV), in a dose-response manner.
- For each standard drink, mixed drinks and liquor had the largest impact on cardiovascular recovery: on average, a single mixed drink increased HR by 2.0% and single shot of liquor lowered HRV by 3.8%.
- For each standard drink, beer had the mildest impact on cardiovascular recovery. However, HR still increased by 1.2% and HRV decreased by 1.6% compared to non-drinking nights, on average.
We analyzed how different alcohol types affect sleep and cardiovascular recovery
We analyzed how different alcohol types affect sleep and cardiovascular recovery in 179 members across 2,600 nights
For 14 days, Eight Sleep members (21+) completed a short morning survey about whether they drank alcohol last night, and if so, which type(s) of alcohol they drank (beer, wine, straight liquor, and/or mixed drinks), how many standard drinks of each type they consumed (see Figure 1), and how long before bed they had their final alcoholic drink. When members drank more than one type of alcohol in a night (e.g., beer and wine), we labeled that night as “2+ types” of alcohol. This allowed us to see whether mixing alcohol types had a larger effect on sleep and cardiovascular recovery. We paired these surveys with biometric data from the Pod: HR, HRV, sleep stages (light, deep, REM), total sleep time, and wake after sleep onset (WASO).
Figure 1. Representation of one standard drink. Members were shown this image to help them determine what one standard drink was for different alcohol types. The chart served as a quick visual reference for volume and glass type, allowing members to easily estimate their drink count based on typical serving sizes without needing to calculate specific alcohol content. Image from: https://alcohol.indianapolis.iu.edu/calculators/alcohol-serving-size.html
Drinking any type of alcohol impairs cardiovascular recovery compared to not drinking
Our analysis revealed a clear pattern: drinking any type of alcohol puts a significant strain on the heart during sleep. On nights when members drank any type of alcohol, sleeping HR increased by at least 1.2%, on average, and HRV decreased by at least 1.6%, on average. Certain types of alcohol were associated with more strain on cardiovascular recovery than others when compared to non-drinking nights. For each standard drink, mixed drinks produced a notably higher increase in HR (+2.0% on average) compared to beer (+1.2% on average; see Figure 2).
Figure 2. Percent change in sleeping HR by alcohol type, per standard drink. The plot shows how different types of alcohol affect HR, compared to no drinks. The y-axis shows the average percent change in HR relative to no drinks. Error bars show standard errors. The x-axis represents the different alcohol types, including No drinks. One standard drink of any alcohol type caused a statistically significant increase in HR compared to no drinks (P<0.05). Asterisks (*) indicate a statistically significant difference compared to beer (P<0.05)
Heart rate variability (HRV) measures the variation in time between heartbeats, and higher is typically better. When HRV drops, it signals your body is under more stress and working harder to recover. When looking at HRV, liquor and wine had more than double the negative effects (-3.8 and -3.6% on average, respectively) compared to beer (-1.6% on average; see Figure 3).
Figure 3. Percent change in sleeping HRV by alcohol type, per standard drink. The plot shows how different types of alcohol affect HRV, compared to no drinks. The y-axis shows the average percent change in HRV relative to no drinks. Error bars show standard errors. The x-axis represents the different alcohol types, including No drinks. One standard drink of any alcohol type caused a statistically significant decrease in HRV compared to no drinks (P<0.05). Asterisks (*) indicate a statistically significant difference compared to beer (P<0.05)
Mixing alcohol types disrupts HRV more than drinking beer alone
When members drank two or more types of alcohol in one night, HRV was significantly lower than when drinking beer alone (-3.0% vs. -1.6%; see Figure 3), but comparable to other single alcohol types. Drinking more than one alcohol type did not impact HR significantly more than drinking a single type of alcohol (+1.6% increased HR; see Figure 2).
Sleep quality after drinking can be saved when sleeping on the Pod
Up to four standard drinks of any alcohol type harm cardiovascular recovery, but not objective or perceived sleep quality when sleeping on the Pod
Across the 14 days, members contributed both drinking and non-drinking nights (about 7 of each on average, with 1.5 drinks on average per drinking night). We saw that on average, as expected, cardiovascular recovery was worse on drinking nights: sleeping HR increased by 3.8% (from 57.7 to 59.9 bpm), and HRV decreased by 10% (from 43.9 to 39.5 ms).
We found a clear dose-response relationship between the number of alcoholic drinks consumed in one night and cardiovascular recovery that night. While one drink increased sleeping HR by 1.4%, the effect compounded: two drinks increased HR by 3.3%, three drinks by 4.3%, and four drinks by 6.9%, on average (see Figure 4). HRV followed the same trend, with HRV decreasing by 3.4% after one drink, 8% after two drinks, 8.6% after three drinks, and 15.3% after four drinks, on average. Interestingly, REM sleep, deep sleep, light sleep, TST, and WASO remained unchanged between drinking and non-drinking nights. This differs from previous research, which shows that REM sleep tends to decrease gradually with each alcoholic drink consumed. Our data indicate that sleep stages and quality remain unchanged even as your heart works harder in the background.
Figure 4. Dose-response relationship between alcohol consumption and cardiovascular recovery. The dots show the average percent change in HR and HRV relative to non-drinking nights across alcohol quantities (0-4 standard drinks), and error bars represent the standard errors. The y-axis shows the average percent change in HR/HRV compared to non-drinking nights. The x-axis represents the number of standard drinks consumed. Asterisks (*) indicate a statistically significant difference compared to 0 drinks (P<0.05).
Notably, members did not perceive a difference in mood or sleep quality between drinking and non-drinking nights, even at higher consumption levels. Members reported no change in mood, hangover symptoms, perceived sleep quality, or feeling refreshed. Even with a significantly decreased cardiovascular recovery (up to 7% higher HR and 15% lower HRV after four drinks), perceived sleep and recovery appeared unaffected.
Since our study only included Eight Sleep members, the Pod’s active temperature regulation may play a role in limiting the negative effects of alcohol. Research indicates that maintaining an optimal body temperature during sleep enhances overall sleep quality. Since the Pod helps maintain your body’s optimal overnight temperature, it may also help maintain normal sleep quality despite alcohol intake.
How to drink alcohol with recovery in mind
If you want to protect your overnight cardiovascular recovery, the data suggests a clear hierarchy:
- Don’t drink at all: The data are clear that the best cardiovascular recovery happens on non-drinking nights.
- Choose wisely: If you do drink, beer will likely be the least disruptive to HR and HRV (regardless of what time you drank), making it the safest bet for protecting recovery.
- Use your Pod: Overnight temperature regulation helps stabilize your sleep even after drinking alcohol (see our recent study here).
Bottom line: While you can’t “sleep off” the cardiovascular stress of alcohol, if you are going to drink alcohol, choosing options like beer can help minimize the impact. Ultimately, skipping alcohol entirely is still the best choice for your cardiovascular recovery.
