Dados do Trabalho

Título

Heart rate reactivity to acute mental stress is blunted in individuals who sleep less than seven hours.

Introdução

Inadequate sleep and stress both have negative impact on health, increasing the risk for negative outcomes such as cardiovascular disease, diabetes and depression. Moreover, the effects of a decrease in sleep time on physiological responses to acute stress still unclear.

Objetivo

To evaluate heart rate reactivity (HRR) after an acute mental stress in individuals who sleep less or more than seven hours.

Métodos

All procedures in this study were approved by the Research Ethics Committee – UESC (CAAE: 94666418.0.0000.5526). A total of 28 undergraduate students (N=10 female) visited the Laboratory of Exercise Psychophysiology (LAPFISIO – UESC) between 08:00am and 11:00am. Volunteers completed seated rest for 15 minutes to measure baseline heart rate (HRBASE) (Polar RS800CX). Then, acute mental stress was induced by serial arithmetic addition test, where, after a period, the speed of numerical presentation increased. The numbers were presented on an audio recording and the volunteer responded verbally. Heart rate was measured again immediately after the acute mental stress (HRSTRESS). HRR was defined as HRSTRESS minus HRBASE. Volunteers then received a self-reported sleep diary to fill and return after seven days. Finally, the volunteers were divided in two groups: Group ≥ 7 = Individuals who slept more than 7 hours (n = 16, 20.7 ± 1.8 years, 65.2 ± 9.4 kg and 169 ± 7 cm) and Group < 7 = Individuals who slept less than seven hours (n = 12, 23 ± 4.4 years, 68.1 ± 15.1 kg and 170.5 ± 7 cm).

Resultados

Independent t-test showed a statistical significant difference (P < 0.001) in total sleep time in Group ≥ 7 (8.1 ± 0.8 hours) compared with Group < 7 (6.17 ± 0.7 hours). In addition, the t-test showed a significant difference (P = 0.02) in HRR in Group ≥ 7 (9.8 ± 6.6 bpm) compared with Group < 7 (1.3 ± 6.1 bpm). Lastly, a significant negative correlation (P = 0.01) was found between the HRR and total sleep time (r = - 0.72) only in the Group < 7.

Conclusões

We conclude that a reduction in total sleep time is associated with a decrease in HRR after acute mental stress in sleep-restricted individuals. Furthermore, it could increase cardiovascular risk due to changes in sympathetic nervous system activity.

Palavras-chave

Sleep, stress and hear rate reactivity