FAMILIAL AGGREGATION OF HEART-RATE-VARIABILITY BASED ON SHORT RECORDINGS - THE KIBBUTZIM FAMILY STUDY

The objective of this study was to assess the familial aggregation of heart rate variability (HRV), a readily measurable noninvasive reflect ion of cardiac autonomic function. Familial correlations were analyzed in 451 kibbutz members aged 15-97 years belonging to SO kindreds. Fiv e-minute duration Holter recordings made during silent supine spontane ous breathing and metronomic breathing were analyzed in the time and f requency domains. The present analysis considers the familial correlat ions and the heritability estimates of two time-domain indices, the st andard deviation (SD) of the R-R interval (RR), reflecting total varia bility, and the root mean square of successive differences in RR inter vals (RMSSD), reflecting vagal (parasympathetic) tone. During free bre athing, age- and sex-adjusted correlations between parents and their c hildren (r = 0.24 for both indices) and between adult siblings above 3 0 years of age (r = 0.24 and r = 0.34 for SD and RMSSD, respectively) were statistically significant, whereas spouse correlations (r = 0.04, r = 0.02 for SD and RMSSD, respectively) and correlations in younger siblings (r = 0.22 and r = 0.01, respectively) were not. Significant h eritability estimates were demonstrated for the two indices (h(2) = 0. 41 for SD and h(2) = 0.39 for RMSSD). These findings suggest that fami lial aggregation of HRV characteristics is determined mostly by geneti c factors and less so by environmental factors and provide a basis for continuing the investigation into the underlying genetic influences o n HRV.