Effect of age on the heritability of sleep quality

Introduction: Poor sleep quality has important consequences for psychological well-being. The quality of sleep has an important genetic influence. Heritability estimates between 34 and 43% have been reported in middle-aged and... [ view full abstract ]

Introduction: Poor sleep quality has important consequences for psychological well-being. The quality of sleep has an important genetic influence. Heritability estimates between 34 and 43% have been reported in middle-aged and young adults, respectively. On the other hand, age has a fundamental influence on this phenotype. Sleep quality deteriorates markedly with age and most of the sleep problems usually increase their prevalence and intensity after adulthood. However, little is known about the variation in genetic influences on sleep quality due to age. Our objective is to analyze the role of age as a possible moderating factor of the heritability of sleep quality.

Method: Sample comprise 1912 subjects (55.9% female), aged 43-71 years (mean = 53.4), participating in the Murcia Twins Registry (644 monozygotic and 1268 dizygotic). Sleep quality was measured using the Pittsburgh Sleep Quality Index. Heritability estimation and moderation analysis were performed using structural equation models.

Results: Heritability of sleep quality in the total sample was estimated at 34% (95% CI: 24-43%), with a significant effect of genetic factors (AE model). No significant effect of shared environmental factors was observed. Age moderated the relative impact of genetic and environmental factors, such that the importance of non-shared environmental factors (E) was significantly reduced in older women. Consequently, heritability increased up to 85% in this age group. No similar effect was found in males. Discussion: Our results are consistent with previous studies that find a moderate genetic influence on sleep quality in the total sample. However, the relative importance of genetic factors appears to increase with age. These results provide new information on the evolution of the differences in sleep quality, between men and women, in adulthood.