Heritability and mortality risk of insomnia-related symptoms: a genetic epidemiologic study in a population-based twin cohort.
Level 3 - non-randomized controlled study
Prospective cohort / twin follow-up study with registry linkage
PubMed 21731146 · doi:10.5665/SLEEP.1136
What was done
The authors analyzed 1990 survey data from the Finnish Twin Cohort (12,502 adults; 1,554 monozygotic and 2,991 dizygotic twin pairs). Self-reported insomnia-related symptoms (general insomnia, sleep onset difficulty, sleep latency, nocturnal awakenings, early morning awakenings, non-restorative sleep) were classified using latent class analysis. Heritability was assessed using quantitative genetic modeling. Mortality data were obtained from national registers through April 2009 (approximately 19 years of follow-up) with multivariable adjustment for smoking, BMI, depressive symptoms, sleep duration, sleep medication use, and sleep apnea symptoms.
What was found
Heritability of individual insomnia symptoms ranged from 34% (early morning awakening) to 45% (nocturnal awakening). Latent class analysis identified three groups: good sleepers (48%), average sleepers (40%), and poor sleepers (12%). The overall sleep cluster had a heritability of 46% (95% CI 41% to 50%). Compared to good sleepers, poor sleepers had higher all-cause mortality (excess mortality 55% in men and 51% in women) after adjusting for smoking, BMI, and depressive symptoms, which persisted after further adjustment for sleep length, sleep medications, and sleep apnea symptoms.
Why it matters
The findings demonstrate that phenotypic insomnia has a moderate genetic component and is an independent risk factor for long-term all-cause mortality.
Limits
Insomnia symptoms and covariates were measured via self-report at a single baseline survey rather than objective sleep measures (e.g., polysomnography or actigraphy). The abstract presents excess mortality percentages rather than hazard ratios or absolute mortality rates. The sample was restricted to a Finnish twin cohort, which may not generalize to other demographic or ethnic groups.
Cited by
- supports Between 28% and 45% of insomnia susceptibility is attributable to genetics.