Gene predicts sleepy performance

Variants of a circadian-rhythm gene predict how well people perform mental tasks when deprived of sleep, according to researchers at the University of Surrey in England.

Earlier studies established that the gene, period3, influences whether an individual is a morning person or a night person. The new work shows that the gene also affects attention span, reaction time, and short-term memory in sleep-deprived people.

Period3 comes in two variants, short and long, and each person carries two copies of the gene. Derk-Jan Dijk and his colleagues studied 24 people carrying either two long versions or two short versions.

After 40 sleepless hours, study participants with the long variant displayed slower reaction times and had more trouble recalling strings of digits than did subjects with the short variant. Performance drop-offs peaked in the early morning—the same time that shift workers and truck drivers report losing concentration, say the researchers.

When finally permitted to sleep, volunteers with the long variant nodded off within an average of 8 minutes, while those with the short variant took 18 minutes to reach dreamland. The long-variant subjects also spent more time in deep sleep, leading the researchers to speculate that these volunteers’ higher “sleep propensity” explains their inferior mental performance when tired.

The research appears in the April 3 Current Biology.

From the Nature Index

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