Cardiovascular autonomic function tests in an African population

BACKGROUND: Diabetes mellitus is becoming increasingly common in sub-Saharan Africa. Autonomic dysfunction contributes to morbidity and mortality in diabetic patients. Data on autonomic dysfunction in the African population is scarce, and no reference values for standardized autonomic function tests are available. The aim of this study was to establish cut off values for five easy-to-use cardiovascular autonomic function tests that may be suitable for resource-poor settings. METHODS: We recruited 276 healthy African individuals, 156 men and 120 women, aged > 20 years. Participants were tested for (1) resting heart rate (HR), (2) HR variation in response to deep breathing, (3) HR response to standing, and (4) postural changes in systolic and diastolic blood pressure (SBP and DBP). Respective cut-off values were calculated according to the 95th or 5th percentile. RESULTS: Taking an association of the autonomic test results with gender and age into consideration, we defined the following cut-off values: resting HR (bpm) ≥ 89 for men and ≥ 97 for women; HR (bpm) in response to deep breathing ≤ 13, ≤ 11, ≤ 9, ≤ 8, and ≤ 7 for age groups 20–29, 30–39, 40–49, 50–59, and 60+ years, respectively; HR (bpm) in response to standing ≤ 14 for 20–29 years, and ≤ 11 for 30+ years; postural decreases in SBP ≥ 17 mmHg for all age groups; and postural decreases in DBP (mmHg) ≥ 2 for men and ≥ 5 for women. CONCLUSION: The test battery revealed cut-off values different from those measured in Caucasians. Further studies are recommended a) to assess whether these cut off values are generally applicable, and b) to establish population specific reference values for Africans.