Indian Asians have poorer cardiovascular autonomic function than Europeans: this is due to greater hyperglycaemia and may contribute to their greater risk of heart disease.
OBJECTIVE
A high prevalence of diabetes contributes to excess CHD in Indian Asians, but the underlying mechanisms are unclear. Heart rate, heart rate variability (HRV) and baroreflex sensitivity (BRS) are measures of cardiac autonomic function that are disturbed by hyperglycaemia and predict CHD. We compared these measures in Indian Asians and Europeans, and sought explanations for the observed differences.


METHODS
A representative sample of 149 Europeans and 151 Indian Asians was recruited from primary care, 66% of them men (aged 35-75 years), 34% women (aged 55-75 years). Heart rate, HRV, BRS and cardio-metabolic profiles were measured over four successive 5 min periods with continuous ECG and blood pressure monitoring.


RESULTS
Indian Asians were hyperglycaemic compared with Europeans (HbA(1c) (mean +/- SD) 6.5 +/- 1.2% vs 5.9 +/- 1.0%, p = 0.001). They had shorter mean RR intervals ((mean +/- SE) 969 +/- 13 vs 1,022 +/- 12 ms, p = 0.002), lower total RR interval power ((geometric mean, 95% CI) 925 [796-1075] vs 1,224 [1,064-1,422] ms(2), p = 0.008) and lower BRS ((mean +/- SE) 5.7 +/- 1.0 vs 6.6 +/- 1.0 ms/mmHg, p = 0.01). All measures of cardiac autonomic dysfunction were significantly associated with hyperglycaemia (mean RR interval vs HbA(1c) r = -0.22; p < 0.001). Ethnic differences in cardiac autonomic function persisted after adjustment for age, blood pressure and medication (mean RR interval 973 vs 1,021 ms, p = 0.004), but were attenuated or abolished by adjusting for HbA(1c) (979 vs 1,014 ms, p = 0.06) or other markers of hyperglycaemia.


CONCLUSIONS
Indian Asians from the general population have impaired cardiovascular autonomic function compared with Europeans. This is due to greater hyperglycaemia in Indian Asians and may determine their increased CHD risk.
Bathula
R
R
National Heart and Lung Institute, Imperial College Academic Health Sciences Centre, 59-61 North Wharf Road, London W2 1PG, UK.
Hughes
A D
AD
Panerai
R
R
Potter
J
J
Thom
S A McG
SA
Francis
D P
DP
Shore
A C
AC
Kooner
J
J
Chaturvedi
N
N
D000328:Adult; D000368:Aged; D044466:Asian People; D001341:Autonomic Nervous System / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001786:Blood Glucose; D001794:Blood Pressure / Q000502:physiology*; D016009:Chi-Square Distribution; D004562:Electrocardiography; D005260:Female; D006331:Heart Diseases / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012307:Risk Factors; D011795:Surveys and Questionnaires; D044465:White People
D001786:Blood Glucose