Fu and Jones found that short sleepers require far less sleep every night and experience no typical adverse health effects, like issues with memory. Later research showed that these short sleepers were also apparently benefiting from the situation, i.e. most short sleepers exhibit optimistic, outgoing, and type A personalities. Fu and Jones published research thinking less about baseline sleep requirements for everyone, and more about individual sleep rhythm. Some people develop significant health problems when deprived of seven to eight hours of sleep per night, others thrive on no more than four or five — and even feel unwell if they get more than that.
Researchers used gene sequencing and a technique known as linkage analysis, which helps scientists pinpoint the exact chromosomal location of mutations associated with a particular trait, to comb through the family’s genome. Their efforts uncovered a single-letter mutation in a gene known as ADRB1 that, like the mutation in DEC2, was associated with natural short sleep.
The cell-based experiments revealed that the mutant form of the beta-1 adrenergic receptor – the protein encoded by the ADRB1 gene, which plays a role in a variety of essential biological processes – degrades more rapidly than the non-mutant version, suggesting that it might also function differently. Using a technique known as optogenetics, in which cells are modified so they can be activated by light, the researchers focused light on neurons in the pons to stimulate those in which ADRB1 was expressed. Triggering these neurons immediately roused sleeping mice – specifically, those that were experiencing non-REM sleep, the sleep phase during which these neurons are not normally active – demonstrating that these neurons promote wakefulness.