COVID-19 can worsen the clinical and functional condition of individuals with chronic diseases such as type 2 diabetes (DM2). There is a lack of knowledge regarding the long-term autonomic and functional impairments of individuals with T2DM affected by COVID-19.

To assess whether individuals with DM2 affected by COVID-19 for one year or more have reduced heart rate variability (HRV) and functional capacity compared to those without a history of this disease.

This cross-sectional case-control study. The sample consisted of individuals with DM 2, with a history of COVID-19 (DMCoV Group), and without a history of COVID-19 (DM Group). All participants had their level of physical activity assessed using the International Physical Activity Questionnaire (short version). Heart rate (HR) and the following HRV measurements were evaluated at rest: standard deviation of normal R-R intervals (iNN) (SDNN); root mean square differences between successive iNN (RMSSD); percentage of successive iNN with difference >50ms (pNN50); low (LF) and high frequency (HF) spectral components in absolute (ms²) and normalized (u.n) units. Functional capacity was evaluated based on the distance covered in the Incremental Shuttle Walking Test (ISWT) in meters. Data distribution was assessed using the Shapiro-Wilk test. Variables with normal distribution are expressed as mean ± standard deviation and the others as median [interquartile range]. Categorical variables were compared using the chi-square test, and numerical variables using the unpaired t-test or the Mann-Whitney test. For all tests, a significance level of 5% was adopted.

Twenty-three individuals of both sexes participated in the study, nine from the DMCov group and fourteen from the DM group (61.78±10.39 years vs. 55.29±9.69 years, P=0.142; 33.3% women vs. 50% women, P=0.669). There was no significant difference in the level of physical activity between the DMCov and DM groups (P=0.235): very active (33.3% vs. 35.7%), active (22.2% vs. 50.0%), irregularly active (22.2% vs. 14.2%) and sedentary (22.2% vs. 0.0%). HR (71.9±10.5 bpm vs. 72.6±11.5 bpm; P=0.876), HRV measurements (SDNN(ms): 39.0±20.8 vs. 25.7± 13.5; P=0.076. RMSSD(ms): 20.7[9.3-57.8] vs. 13.2[9.1-26.7]; P=0.403. pNN50(%): 2 ,2[0.5-27.0] vs. 0.4[0.0-2.7]; P=0.159. LF(ms²): 346.0[65.0-614.0] vs. 199 ,0[29.5-343.5]; P=0.277. HF(ms²): 125.0[26.5-705.0] vs. 82.0[26.8-253.8]; P= 0.439 LF(un): 64.2±16.8 vs. 59.4±17.4 P=0.518 HF(un): 35.6±16.8 vs. 40.2±16.7; P=0.528) and functional capacity (272.5±112.7 meters vs. 373.9±105.6 meters; P=0.051) showed no significant difference when comparing the groups DMCov and DM.

COVID-19 did not impair long-term cardiac autonomic modulation in individuals with T2DM. On the other hand, the fact that individuals with a history of COVID-19 walked an average of a hundred meters less on the ISWT compared to those without this history suggests impairment of functional capacity caused by COVID-19.

The findings of this study are preliminary and point to the need for future investigations involving a larger sample size and including other measures of modulation and cardiac autonomic function to confirm the results found.