Sleep disruption and next-morning task impairment did not track together in a small controlled intranasal-methamphetamine study. The result does not establish that disrupted sleep is harmless; it shows that different outcomes require separate measurement.
Perez and colleagues studied 11 non-treatment-seeking methamphetamine users in a residential, double-blind, within-participant experiment. Separate blocks involved intranasal placebo or methamphetamine at 12, 25 or 50 mg per 70 kg. Dosing occurred in the morning, with lights out that evening and residual effects assessed the next morning.
Investigators collected subjective sleep reports, movement-based sleep estimates, plasma methamphetamine, cardiovascular measures, mood ratings and psychomotor performance. The single-dose design did not reproduce repeated dosing over a prolonged binge.
The 25- and 50-mg doses disrupted subjective sleep measures. Significant objective sleep disruption occurred at the largest dose. At 50 mg, participants reported nearly five fewer hours of sleep, whereas actigraphy suggested approximately two fewer hours.
Objective sleep data were available for only six of the 11 participants. That smaller denominator limits the comparison and prevents treating actigraphy as a complete account of every participant’s sleep.
The largest dose increased next-day physiological measures, and some mood measures were affected. The study did not detect negative residual effects on the early next-day performance tests. Those null findings belong alongside the sleep and physiological findings, rather than replacing them.
Performance on a selected morning test battery does not represent every demanding activity, sustained driving or later-day fatigue. A small experiment can also miss effects that a larger or more challenging protocol might detect.
The paper supports distinguishing perceived sleep loss, movement-based sleep estimates, physiological persistence and measured task performance. A detectable plasma drug concentration is another separate endpoint. None of these can be exchanged automatically for a finding about an individual driver’s ability.
Related reading: What a controlled driving study can establish.