Background: While heritability has been shown for daytime sleepiness, the heritability of daytime capillary oxygen saturation (SpO(2)) has not been described in detail. Our aim was to estimate the role of genes and environmental factors--both shared and unshared--in the variation of daytime SpO(2).
Methods: A total of 193 adult healthy twin pairs (138 monozygotic, 55 dizygotic) were recruited in Hungary and in the United States [age = 43.6 ± 15.6 years (mean ± SD)]. SpO(2) was measured by pulse oximetry. Univariate quantitative genetic modeling was performed to decompose the phenotypic variance of the considered parameter into heritability (A), shared (C), and unshared (E) environmental effects.
Results: SpO(2) twin correlation in monozygotic twins was stronger than in dizygotic twins (0.30 and -0.15, respectively, p < 0.05). Age-, sex-, country-, and body mass index-adjusted genetic effects accounted for 26 % (95 % CI 10, 45 %) of the variance of SpO(2), and the unshared environmental component explained the remaining 74 % (95 % CI 59, 89 %). No shared environmental influence on SpO(2) was detected. The heritability of SpO(2) was not different between smokers and nonsmokers.
Conclusion: In summary, individual differences in daytime SpO(2) are explained by genetic and unshared environmental effects. The strong unshared environmental influence highlights the role of prevention of known environmental risk factors.