Interindividual variability in static apnoea performance is partly explained by genetic factors

A large interindividual variability exists in maximal apnoea duration and the physiological adjustments that occur during apnoea. Although a few genes have been found to be associated with some of the cardiovascular responses during apnoea, the extent to which genetic and environmental factors contribute to individual differences in apnoea performance has not been studied. Accordingly, 12 monozygotic and 10 dizygotic twin pairs (n = 44) performed a series of five maximal apnoeas with the face immersed in cold water to determine the heritability estimates for apnoea duration and the accompanying haemodynamic adjustments. Heritability estimates were derived and showed that genetic factors explain a substantial portion of the interindividual differences in maximal apnoea duration (82%) and in the mean arterial pressure (74%) and diastolic pressure (73%) responses to apnoea. Additionally, genetic influences accounted for 77% of the variability in forced vital capacity. Nonetheless, the heritability estimates for heart rate, systolic pressure, stroke volume, cardiac output and total peripheral resistance could not be calculated, since the statistical assumptions required to estimate genetic variance were not met. Overall, it appears that a large portion of the variability observed in maximal static apnoea duration and the arterial pressure response can be explained by genetic differences. It should be emphasised that heritability estimates reflect the proportion of the variance for a trait and do not imply biological determinism. The significant heritability observed for apnoea duration likely reflects contributions from multiple genetically influenced physiological systems but might also be influenced by unmeasured shared environmental factors.