Bryan Johnson's pre-sleep practice.

Bryan Johnson is the tech founder who decided to spend the back half of his life trying not to age. He runs an elaborate longevity protocol (dozens of supplements, hours of measurement, a diet most people would call grim), and he publishes the lot. We're not endorsing the whole programme; large parts of it are unreplicated, expensive, and built around a sample size of one. What's interesting is the small practice he sticks to every night before bed.

He does ten minutes of 4:6 breathing. In through the nose for four seconds, out for six. Here is how he describes it in his evening routine:

HRV measures the variability between heartbeats. A higher HRV reflects a more resilient nervous system.

I do 10 min of 4:6 breathing before bed. That's breathing in through the nose for 4 seconds and out for 6. It activates your parasympathetic nervous system, elevating your HRV and calming you for sleep.

HRV, or heart-rate variability, is the variation in the time between consecutive heartbeats. Higher variability generally means a more adaptable autonomic nervous system, one that can shift between alert and at-rest states without getting stuck. Slow breathing is one of the few levers that move it on demand, mostly through the vagus nerve, which carries the parasympathetic signal that slows the heart on each exhale. If you want the longer explainer, the journal entry on HRV and breath goes deeper.

The reason a longer exhale matters is mechanical. The vagus nerve fires harder during exhalation; the heart slows; blood pressure dips; the parasympathetic branch gets its turn at the wheel. A short inhale and a long exhale shifts the balance of the breath cycle toward that calming half. Paul Lehrer and others have shown that four to six breaths per minute lifts HRV reliably in healthy adults. 4:6 lands at six breaths a minute, right at the top of that band. Bryan's claim that this elevates HRV and calms you for sleep is consistent with the research, though the literature itself uses softer language than “elevates”: the effects are real, they are also modest, and they accumulate with practice rather than appearing in a single session.

When is 4:6 worth reaching for. Before sleep is the obvious one: the parasympathetic shift is what you want as you wind down. After a long day, when the body is still wired but the work is done. In the gap between a hard meeting and whatever is next. The asymmetric rhythm feels different from 5:5 coherent or 6:6 resonant; both of those land in roughly the same HRV band, but the longer exhale in 4:6 reads as actively releasing rather than evenly oscillating. Some people find it easier as a wind-down precisely for that reason.

Ten minutes is what Bryan does. One or two minutes is enough to start. If you want to try ten minutes of 4:6 now, the player will run it for you, eyes open, no setup. Or pick a shorter length and see how it lands.