Abstract
Objectives
Food insecurity (FI) is prevalent among low-income adults and is related to increased stress. Heart rate variability (HRV) is associated with adverse health and a known indicator for stress vulnerability. However, the relationship between FI and HRV is unclear. Our study aims to study the associations between FI and ultra-short-term HRV (5 minutes) at daily basis.
Methods
A total of 22 healthy low-income adults were recruited in fall 2019 and 18 were followed up in winter 2020. Data on FI and HRV were collected over a 3-week-long wave in each surveyed month (2nd – 4th week). Daily FI was assessed using the adapted USDA adult module on the provided smartphones. Each day, a 5-minute heart rate was recorded using the Polar H7 sensor, yielding a number of HRV metrics in two domains. SDNN, Rmssd, and pNN50 are time-domain metrics quantifying the amount of variability in interbeat interval (the higher the ‘better’). LF/HF Ratio is a frequency-domain metrics estimating the distribution of power into frequency bands (the lower the ‘better’). The Time Varying Effect Models were used to estimate the association between daily FI and ultra-short-term HRV metrics as a function of study day.
Results
A total of 606 person-days (response rate = 72.1%) of data in FI and HRV was collected. In fall, higher FI score was significantly associated with lower lnRmssd at day 19 (b = −0.13) and 20 (b = −0.12), lower Pnn50 at day 20 (b = −0.13), and higher LF/HF ratio from day 1 to 5 (b ranges 0.29–0.88). In winter, higher FI score was related to lower lnRmssd at day 18 (b = −0.24) and 19 (b = −0.27), lower Pnn50 from day 17 to 19 (b ranges −10.99 to −7.79), and higher LF/HF ratio from day 9 to 11 (b ranges 0.78–1.22) and day 18 to 20 (b ranges 1.17–2.40).
Conclusions
Across the 2 months spanning two seasons, our pilot study found that daily FI was significantly and consistently associated with suboptimal time-domain HRV metrics in the last few days of the study months. Results for the frequency-domain also support a time-varying impact of FI on HRV. The preliminary results support a potential more profound impact of FI on stress vulnerability, particularly by the end of the months.
Funding Sources
The National Center for Advancing Translational Sciences, National Institutes of Health (UL1TR002014) and the Broadhurst Career Development Professorship for the Study of Health Promotion and Disease Prevention.
Shape-shift contagion in emerging markets equities: evidence from frequency- and time-domain analysis
