BACKGROUND:
Veterans with post-traumatic stress disorder (PTSD) have higher risk of coronary heart disease (CHD) incidence and mortality. Psychological conditions may have an adverse effect on the autonomic nervous system, and may in part have genetic origins. Novel non-linear measures of heart rate variability (HRV), such as fractal dimension (FD) and power law slope have been associated with mortality and may signify autonomic dysfunction. We hypothesized that PTSD is associated with reduced FD and increased power law slope, suggesting higher mortality risk.
METHODS:
FD and power law slope were measured from 24-hour Holter recordings in 416 predominantly healthy middle-aged male twins from the Vietnam Era Twin Registry. Current (symptoms within the past month) and remitted (past history of) PTSD were measured using the Structured Clinical Interview for Psychiatry Disorders. Mixed-effect regression models were used to adjust for twin clustering and account for genetic/familial influences.
RESULTS:
The mean age was 56 ± 3 years, 35 had current PTSD, and 46 had remitted PTSD. In models that analyzed twins as individuals, current PTSD was significantly associated with 22% reduced FD and 18% increased power law slope. This association persisted for power law slope after adjustment for traditional risk factors, lifestyle factors, depression, and anti-depressant medication use (table). After controlling for genetic/familial factors by comparing twin brothers discordant for current PTSD within pairs (20 pairs), both measures remained significantly associated with current PTSD. Remitted PTSD did not influence HRV measures. No interaction by zygosity was found.
CONCLUSIONS:
Vietnam era veterans with PTSD have reduced FD and increased power law slope persisting after multivariable adjustment. This suggests that autonomic mechanisms, independent of genetic and familial effects, may contribute to increased CHD and mortality in veterans with PTSD.
Post traumatic stress symptoms and heart rate variability in Bihar flood survivors following yoga: a randomized controlled study
