Dispassionate types that we are, The Economist tends not to dwell on matters of the heart (although the caveman’s guide to romance in last week’s Culture section was a welcome Valentine’s Day tonic). But when the topic is physiological we’re on firmer ground. “Heart-rate variability” (HRV), the subject of a recent Well Informed column, is a health indicator gaining lots of attention. Smart watches and fitness trackers can measure how regularly spaced your heartbeats are, giving in effect an “accumulated stress” score. But, as our column explains, this on its own doesn’t tell you much. Without careful interpretation, obsessing over HRV might just add to your stress levels.

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