Sleeping better doesn't mean functioning better the next day
It's an observation many people with insomnia have made: a treatment can improve sleep data, but the next day still feels hard. Fatigue, reduced concentration, irritability. The numbers improve, but daily life doesn't.
A 2026 study from researchers at the University of Maryland offers an explanation: we're measuring the effectiveness of insomnia treatments with the wrong indicators.
What the study found
Current insomnia treatments, whether cognitive behavioral therapy and sleep coaching or medication, are primarily evaluated on nighttime metrics: sleep onset latency, sleep efficiency, time awake during the night.
The Maryland researchers argue these indicators don't capture what actually matters for patients. The clinically meaningful goal of an insomnia treatment isn't to improve polysomnography numbers. It's to improve the person's daytime function: cognitive performance, emotional regulation, work effectiveness, and perceived quality of life.
A treatment that improves nighttime sleep without improving daytime function hasn't actually reached its objective.
What this changes for active people
For athletes and people who train regularly, this distinction is particularly relevant. Most wearables measure sleep duration and efficiency, and some provide recovery scores based on this data.
But if daytime function is the real indicator of recovery quality, then a high sleep score doesn't guarantee optimal recovery. And conversely: an imperfect sleep score can be compatible with good functional recovery.
Integrating daytime function into recovery assessment, beyond just nighttime metrics, changes how you should interpret your wearable data.
Practical daytime function assessment
Without standardized tools, self-assessment of daytime function uses a few simple indicators:
Concentration: can you work or train with normal attention in the morning? Do complex tasks require unusual effort?
Emotional regulation: are your emotional responses proportionate? Irritability and heightened reactivity are classic signals of incomplete recovery.
Physical energy: does physical effort in the first 30 minutes of a session feel normal, or does it take more effort to reach the same intensity?
These subjective indicators, combined with your wearable data, give a more complete picture of your actual recovery than nighttime sleep metrics alone.