What Is a Good HRV for a 40 Year Old?

Reference resting HRV (RMSSD) for men and women aged 40 to 49, how to read a wearable reading against it, and what the evidence says a high or low number means at this age.

For a woman in her early 40s, the median resting HRV is 33.9 ms, falling to 29.2 ms by her late 40s. For a man the median is 29.0 ms in the early 40s and 26.0 ms in the late 40s. Those are medians of RMSSD from 10-second resting ECGs in 84,772 healthy Dutch adults, and the spread around them is wide: the normal range for healthy women aged 40 to 44 runs from 9.7 to 123.7 ms. So a reading well under the median is common in people with nothing wrong, and no single number marks "good". The more useful comparison is your own trend. A ring or watch reading is also not directly comparable with this table, because it is taken overnight and, on Apple Watch, uses a different HRV formula altogether.

Median HRV for your 40s, by sex

The reference set is split into five-year groups, so the 40s have two rows. Read your sex and your half of the decade.

How fast HRV falls through the 40s

The drop inside this one decade is steep. The women's median goes from 37.9 ms at 35 to 39, to 33.9 at 40 to 44, to 29.2 at 45 to 49. The men's goes from 32.8 to 29.0 to 26.0. A woman who records 35 ms at 38 and still 35 ms at 48 moves from below the median for her age to above it without anything changing in her body.

Women run higher than men through most of adult life in this dataset: on average 5.02 ms higher at the median between 20 and 45, narrowing to 2.53 ms between 45 and 59, with no sex difference reported above 60 (European Journal of Preventive Cardiology, 2020). The 40s are where that gap starts to close.

One more reading note. The mean HRV for women aged 40 to 44 was 41.0 ms against a median of 33.9, because a minority of very high readings pull the average up. An "average HRV for a 45 year old" quoted from a mean will look higher than what the typical person actually records. KnowYourPrime's HRV desk rates the age decline itself as Established, and HRV by age has every age group from 13 upward.

Why your ring or watch will not match this table

The reference values come from a 10-second ECG taken at rest during the day. Consumer devices measure something else. Fitbit and Pixel Watch calculate RMSSD over your longest sleep period, according to Google's own documentation. Oura shows an average HRV across the night from five-minute samples, according to Oura's documentation. Apple Watch reports SDNN, a different HRV calculation on a different scale, as Apple's HealthKit documentation shows, so an Apple figure cannot be read against an RMSSD table at all.

Time of day alone changes the number. In data from 8,203,261 Fitbit users, HRV showed strong variation across the day, so a night-time average and a daytime ECG are not the same measurement (The Lancet Digital Health, 2020). That study was funded by Fitbit.

Device accuracy then varies by brand. Against an overnight ECG in 13 adults across 536 nights, Oura Gen 4 had a mean absolute percentage error of 5.96 percent, Whoop 4.0 8.17 percent, Garmin Fenix 6 10.52 percent and Polar Grit X Pro 16.32 percent (Physiological Reports, 2025). Our desk rates consumer wearable HRV accuracy as Uncertain. Wrist and ring HRV versus ECG goes into the detail.

What explains the difference between you and another 45 year old

Less than most HRV advice implies. In 149,205 Lifelines participants, age and sex together explained 17.4 percent of the differences in RMSSD between people. Physical activity, alcohol and smoking showed some associations, but adding all lifestyle and psychosocial factors explained less than an extra half a percent, and stress, social well-being and neuroticism showed no association at all (Heart Rhythm, 2018).

That is a statement about differences between people, not about your own number over time. Within one person, HRV does respond: our desk rates the effect of alcohol as Established and scaling with how much is drunk (how long alcohol lowers HRV), and rates regular exercise training raising HRV as Established, with most of that trial evidence from people with a heart condition (how often to exercise for HRV). GLP-1 drugs such as Ozempic raise resting heart rate and lower HRV in trials in people with type 2 diabetes, which our desk also rates Established (Ozempic and HRV).

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