Background: The analysis of the fluctuations of the successive R-R intervals, called heart rate variability (HRV), is an indirect and non-invasive marker of the modulation of the sympathetic and parasympathetic nervous systems on the heart. The reliability of the HRV indexes is subject to compliance with specific standards including the evaluation framework. However, no standard specifically defines the temperature conditions of the assessment room. The aim of this investigation lies in the accessibility of this tool in sub-Saharan Africa because costs required to control the temperature of assessment room.

Purpose: Evaluate the influence of the temperature conditions of assessment room on linear indexes of heart rate variability.

Methods: This is a prospective cross-sectional analytical and descriptive study. 80 healthy male volunteers were divided into 2 groups; "Young" (n = 40, 28.2 ± 5.45 years, 21.92 ± 2.59 kg/m²) and "Adults" (n = 40, 48.85 ± 5.23 years, 25.55 ± 2.96 kg/m²). The time intervals between consecutive heartbeats have been registered, in supine position, for 15 min using a Polar heart rate monitor, model RS800CX (Polar Electro Co. Ltd. Kempele, Finland) during two recording conditions: controlled temperature (between 22 and 24 °C) and ambient temperature (between 30 and 32°C). The comparison of different HRV indexes obtained was performed with ANOVA two ways, because the data showed a normal distribution after performing the Kolmogorov-Smirnov test.

Results: The volunteers in the "Young" group exhibited the highest values ​​of the SDNN (Standard deviation of  NN intervals, p = 0.01), RMSSD (Root mean square of successive RR interval differences; p <0.001), pNN50 (Percentage of successive RR intervals that differ by more than 50 ms, p <0.001) and HF nu (Relative power of the high-frequency band (0.15–0.4 Hz) in normal units, p = 0.002), while "Adults" volunteers have the highest values ​​for the LF nu (Relative power of the low-frequency band (0.04–0.15 Hz) in normal units, p = 0.002). The evaluation of the effects of temperature conditions on linear indices of HRV of the volunteers showed that in both groups, the values ​​of all the linear indices of HRV were similar between the two assessment conditions.

Conclusion: The results confirm that aging reduces the values of the linear indices of HRV. The main result of this study is that the variation of the temperature of evaluation room did not modify these indices.

Implications: These findings suggest that the measurement of HRV indexes in the time and frequency domains could be done in sub-Saharan Africa without control of the temperature of assessment room. This means greater applicability of this method, given the socio-economic conditions of the region.

Keywords: Sub-Saharan Africa; Heart rate variability; Room temperature.

Funding acknowledgements: None

Ethics approval: Did this work require ethics approval? : YES. The University Clinic of Physical Medicine and Rehabilitation of CNHU-HKM of Cotonou where this study took place approved it.