By Lucy Piper, Senior medwireNews Reporter
Researchers have quantified the contribution genetics makes to sleep quality variation in a twin study of middle-aged men.
They found that additive genetic effects explained 34% of the variability in individual sleep quality, while 66% was attributed to individual-specific environmental factors.
Common environmental factors made no contribution, however, report the researchers, led by Brinda Rana (University of California, San Diego, USA).
“Understanding the etiology of sleep disorders has significant public health implications,” they comment in the Journal of Sleep Research. “Examining the extent to which genes and the environment impact the development of sleep disorders may help to inform treatment approaches.”
The team carried out a classical twin study, involving 1218 men, aged an average of 55 years, who were participating in the Vietnam Era Twin Study of Aging.
The average Pittsburgh Sleep Quality Index (PSQI) score for the group was 5.6, with scores ranging from 0 to 20 on a scale of 0 to 21. Forty percent of the participants were classified as having poor sleep, based on a global PSQI score above 5.
In addition to explaining 34% of global PSQI score variability, heritability made a similar contribution to six of the seven individual components of the PSQI, with estimates ranging from 23% for sleep disturbance to 34% for sleep latency.
The only exception was use of sleep medication, to which heritability made no contribution. Rather, common environmental factors accounted for 31% of variance and unique environmental factors the remaining 69%.
Rana and team suggest that the next steps should be to “identify specific environmental factors and specific genes that influence sleep quality and disorders in order to focus prevention and intervention strategies.”
They note that different sets of genes may contribute to sleep quality during different periods of life, and it is possible that the impact of the environment may be dependent on specific genes.
“If this were the case, genes may play a larger role than is suggested in the present study,” they say.
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