Reduced physiological complexity in robust elderly adults with the APOE ε4 allele

Background: It is unclear whether the loss of physiological complexity during the aging process is due to genetic variations. The APOE gene has been studied extensively in regard to its relationship with aging-associated medical illness. We hypothesize that diminished physiological complexity, as measured by heart rate variability, is influenced by polymorphisms in the APOE allele among elderly individuals. Methodology/Principal Findings: A total of 102 robust, non-demented, elderly subjects with normal functions of daily activities participated in this study (97 males and 5 females, aged 79.2±4.4 years, range 72-92 years). Among these individuals, the following two APOE genotypes were represented: 4̇non-carriers (n = 87, 85.3%) and 4̇carriers (n = 15, 14.7%). Multi-scale entropy (MSE), an analysis used in quantifying complexity for nonlinear time series, was employed to analyze heart-rate dynamics. Reduced physiological complexity, as measured by MSE, was significantly associated with the presence of the APOE 4̇allele in healthy elderly subjects, as compared to APOE 4̇allele non-carriers (24.6±5.5 versus 28.9±5.2, F = 9.429, p = 0.003, respectively). Conclusions/Significance: This finding suggests a role for the APOE gene in the diminished physiological complexity seen in elderly populations.