Age-related reductions in heart rate variability do not worsen during exposure to humid compared to dry heat: A secondary analysis. Issue 4 (2nd October 2019)

• Record Type: Journal Article
• Authors: Carrillo, Andres E.; Flouris, Andreas D.; Herry, Christophe L.; Notley, Sean R.; Macartney, Michael J.; Seely, Andrew J.E.; Wright Beatty, Heather E.; Kenny, Glen P.
• Is Part Of: Temperature. Volume 6:Issue 4(2019)
• Page Start: 341
• Page End: 345
• Publication Date: 2019-10-02
• Subjects: Aging -- autonomic nervous system -- parasympathetic nervous system -- sympathetic nervous system -- relative humidity -- heat stress; Thermobiology -- Periodicals; Thermotherapy -- Periodicals; Body temperature -- Regulation -- Periodicals; Body temperature -- Regulation; Thermobiology; Thermotherapy; Periodicals; 571.46
• DOI: 10.1080/23328940.2019.1684791
• Languages: English
• ISSNs: 2332-8940

Abstract

ABSTRACT: We conducted a secondary analysis to investigate whether age-related attenuations in heart rate variability (HRV) worsen during exposure to moderate, dry (36.5°C, 20% RH) or humid (36.5°C, 60% RH) heat conditions that resulted in greater body heat storage among older compared to young participants, and during humid compared to dry heat, regardless of age. Six HRV indices [heart rate (HR), coefficient of variation (CoV), detrended fluctuation analysis: α1, low frequency power, high frequency power, and low/high frequency ratio] were assessed in 10 young (21 ± 3 y) and 9 older (65 ± 5 y) adults for 15-min prior to (baseline), and at the end of a 120-min exposure to dry and humid heat while seated at rest. Our results demonstrated a condition (dry and humid) x time (baseline and end) interaction effect on HR (p = 0.047) such that HR gradually increased during humid heat exposure yet remained similar during dry heat exposure across groups. We also found an age-related attenuation in CoV at baseline for both the dry (young: 0.097 ± 0.023%; older: 0.054 ± 0.016%) and humid (young: 0.093 ± 0.034%; older: 0.056 ± 0.014%) heat conditions (p < 0.02). Those age-related attenuations in CoV, however, were not magnified throughout the exposure nor different between conditions (p > 0.05). While older adults stored more heat during a brief 120-min exposure to dry heat compared to their young counterparts, this was not paralleled by further age-related impairments in HRV even when body heat storage and cardiovascular strain were exacerbated by exposure to humid heat.