Yes. Nicotine lowers heart rate variability (HRV) whether it arrives in smoke or vapour. In 4,751 adults from the general population, each extra 10 grams of tobacco a day went with 9.8% lower SDNN SDNN The standard deviation of all NN intervals in a recording, in milliseconds. It measures overall variability, and its value depends strongly on how long the recording lasts. More about SDNN and 8.9% lower RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next, in milliseconds. It mainly reflects vagal activity. More about RMSSD on a 20-minute ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG (Murgia and colleagues, 2019). In a lab, a 30-minute session on a nicotine e-cigarette shifted HRV toward the sympathetic Sympathetic nervous system The "fight or flight" branch of the autonomic nervous system. It speeds up the heart and makes it pump harder, but it acts too slowly to drive beat-to-beat HRV. More about Sympathetic nervous system (“fight or flight”) side, while the same device without nicotine did nothing (Moheimani and colleagues, 2017).
What nicotine does to the heartbeat
Nicotine releases adrenaline and noradrenaline, the messengers of the sympathetic branch. The heart speeds up, the vessels tighten and the vagal brake that creates most beat-to-beat variation eases off. Short-term HRV measures such as RMSSD and high-frequency power HF power The variance of the heartbeat intervals that falls in the 0.15 to 0.40 Hz band, in ms²: the range of normal breathing. It mainly reflects vagal activity when breathing is 9 to 24 breaths a minute. More about HF power follow that brake, so they fall. A 2024 review of the factors that shape HRV lists harmful substances, including tobacco, among the external factors linked with lower values (Sammito and colleagues, 2024).
What the studies found
Smoking, dose by dose. The South Tyrol study recorded 20-minute ECGs in 4,751 adults and asked about current smoking, pack-years and grams a day. Among current smokers, HRV fell with intensity: 9.8% lower SDNN, 8.9% lower RMSSD, 20% lower total power Total power The sum of the power in every band of the spectrum, in ms²: the variance of the heartbeat intervals. For a 5-minute recording it is VLF + LF + HF; over 24 hours ULF is added. More about Total power and 19% lower high-frequency power for every 10 grams of tobacco a day, after accounting for heart conditions and medicines. In current smokers, each 5 pack-years of history took another 2% to 5% off. The LF/HF ratio LF/HF ratio LF power divided by HF power, with no unit. It was proposed as a gauge of balance between the sympathetic and parasympathetic systems, but research shows it cannot measure that reliably. More about LF/HF ratio did not move, which the authors read as both branches being affected rather than a simple imbalance.
Vaping, long term. At UCLA, 23 habitual e-cigarette users aged 21 to 45 who were not current smokers were enrolled alongside 19 non-users. After excluding people with blood signs of recent cigarette use or of vaping that day, the main comparison was 16 vapers against 18 non-users. The vapers had lower high-frequency HRV (46.5 against 57.8 normalised units Normalised units LF or HF power as a percentage of their sum (LF + HF), rather than in ms². The two always add up to 100, so they carry one piece of information between them. More about Normalised units ) and a higher LF/HF ratio (1.37 against 0.85), a pattern the authors called sympathetic predominance. It was present even with no detectable nicotine in the blood, so it was not just the last puff (Moheimani and colleagues, 2017, JAMA Cardiology). A cross-sectional comparison of 34 people cannot prove cause, and the study did not include tobacco smokers for comparison.
Vaping, right now. The same group then had 33 healthy non-smokers use, on different days, an e-cigarette with nicotine, one without, and a sham, for up to 30 minutes each, with HRV recorded before and after. Only the nicotine condition produced a clear shift: lower high-frequency power, higher low-frequency power LF power The variance of the heartbeat intervals that falls in the 0.04 to 0.15 Hz band, in ms²: rhythms repeating every 7 to 25 seconds. Once read as sympathetic activity, which is now disputed. More about LF power and a higher LF/HF ratio. The authors concluded the acute effect comes from the inhaled nicotine, not the other ingredients.
Quitting. In the South Tyrol study, past smokers had higher HRV than people who had never smoked, whatever their pack-years. The authors took that as smoking cessation being linked with higher HRV. The study could not say how fast the recovery happens. An older crossover study in 39 male smokers found higher 24-hour high-frequency power and pNN50 pNN50 The percentage of neighbouring NN intervals that differ by more than 50 milliseconds. It tracks fast, vagally driven changes, like RMSSD, but as a share rather than a size. More about pNN50 after one week without cigarettes than after a week of usual smoking (Minami and colleagues, 1999).
How to read your own data
- Tag nicotine, including late use. A vape or cigarette in the evening may show in the first hours of sleep. Compare those nights with your usual range using the method in building your HRV baseline.
- Keep the morning routine fixed. If you take a short morning reading, take it before the first cigarette or vape every day, or the readings will not be comparable.
- Expect a slow rise after quitting. Watch the 7-day average over the first month or two rather than any single morning. Sleep, mood and appetite change too in the first weeks, and they move the number as well.
- Remember the other habits. Smoking often travels with coffee and alcohol; each has its own effect.
For the lever-by-lever evidence on raising HRV, see how to increase HRV.
When to talk to a doctor
If you want to stop smoking or vaping, a doctor or pharmacist can offer support and medicines that raise your chances. Talk to a doctor about any chest pain, breathlessness, palpitations or an irregular pulse, whatever your HRV shows. HRV cannot diagnose anything, and this page is not medical advice.