Column · sleep leading indicator
A lagging indicator tells you what already happened. A leading indicator changes what you do tonight. Sleep sits in the second category because its effect on the following day is immediate and large.
Decision quality, patience, appetite regulation, and the willingness to do difficult things. In practice, a short night does not only make you tired; it makes you choose the easier option repeatedly.
Because it feels like a symptom rather than a cause. People record it when it is bad and stop when it improves, which destroys the series exactly when it becomes useful.
Hours slept, and one word for quality, recorded every day. Thirty days of that is more informative than any single test, because it shows the relationship between the number and the days that followed it.
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