Cognitive performance is rock bottom just after waking

Sleep deprivation is bad for performance, but being woken up is worse. In a laboratory experiment, adult volunteers performing a series of random adding tests scored lower in the three minutes after waking than they did at any time over the next 24 hours. One minute after waking, their scores were only 65% of their best, significantly worse than all other test scores during the experiment, including the test done after a whole night without sleep (P ≤ 0.01). After 20-60 minutes awake, the volunteers had bounced back to over 80% of their peak performance.

The experiment was small but carefully done. The nine healthy volunteers had no caffeine, alcohol, nicotine, or drugs (recreational or medicinal) for three weeks before the study. For the same period they logged a regular eight hours' sleep every night.

The results suggest that cognitive performance is worst just after waking, which has obvious implications for on-call doctors, truck drivers, soldiers, and others who are woken from sleep to do complex tasks more or less immediately.

Simple strategy for diagnosing pulmonary embolism looks safe

Diagnosing pulmonary embolism can be a complicated, multistage process. In an attempt to simplify it, Dutch doctors developed a new more straightforward approach. Firstly, decide whether pulmonary embolism is likely or unlikely using a simplified version of the Well's rule. If pulmonary embolism is unlikely, do a d-dimer test. If that's negative, withhold anticoagulants. For everyone else, go straight for computed tomography and rely on the results to make a treatment decision.

It seems to work. In a large trial of 3306 patients with suspected pulmonary embolism, treatment was withheld from 1028 who were classed as “unlikely” to have embolism and had a negative d-dimer test result. Over the next three months, only five of them (0.5%, 95% CI 0.2% to 1.1%) developed venous thromboembolism. Treatment was …