Heart rate variability related to season of birth: A replication study

Abstract

Low heart rate variability (HRV) has strongly been associated with an increased risk for cardiovascular disease. With cardiovascular disease being the number one cause of global deaths, factors that influence its development are relevant to understand. Season of birth has been suggested as one of the factors influencing the development of HRV. The current study was set up to replicate the finding that men born in winter have higher HRV later in life compared to those born in other seasons. To this end, we studied a sample of 1,871 healthy participants from the Brain Resource International Database during rest and during task. Furthermore, sex and age differences and associations with personality traits and psychiatric symptoms were explored. We replicated the earlier finding that men born in winter have a lower ratio of low frequency (LF) power to high frequency (HF) power during rest compared to summer and fall, and, although less pronounced, higher HF compared to summer. A difference between summer and winter for LF/HF in men was internally replicated using data recorded during task. Additionally, for both sexes, LF/HF ratio increased with age, and LF and HF both decreased. In general, LF/HF was lower in women, but heart rate was higher. In men, low HRV was associated with depression and the personality trait openness. In conclusion, results from a large multicenter data set covering the entire lifespan demonstrate that HRV changes with age in both sexes and confirm that season of birth influences HRV later in life in men.

Keywords: aging; heart rate variability; season of birth; sex differences.

Figure 1

Heart rate variability plotted for different seasons of birth. Top: Variation in high frequency (HF [ln (ms²)]). Bottom: Variation in low frequency relative to high frequency (LF/HF [ln (ratio)]). Left: Original results from Huang et al. (2015). Middle and right: Results from the current study for the eyes open resting state and oddball performance conditions, respectively. Significance between each season (green) in relation to winter (blue) are indicated. Cohen's d' effect sizes are provided in the columns for the significant comparisons found in Huang et al. *p ≤ .05; ***p ≤ .001

Figure 2

HRV across the lifespan, separated for men (brown dots and line) and women (blue dots and line). Depicted HRV metrics are (a) meanRR interval, (b) LF, and (c) HF