Body mass index is likely to be an inconsistent measure of obesity in Māori and Pacific patients, according to a study by University of Otago researchers. Specifically, researchers from HeartOtago - a group of cardiovascular researchers and clinicians located at the University and Dunedin Hospital - looked at epicardial adipose tissue (EAT), a special form of fat surrounding the heart which has been linked to increased risk of heart attacks and disturbances in heart rhythm. Their aim was to investigate the correlation between EAT and BMI in different ethnic groups in New Zealand.
In their study, ‘Correlation Between Epicardial Adipose Tissue and Body Mass Index in New Zealand Ethnic Populations’, published in the New Zealand Medical Journal, they used echocardiography (ultrasound of the heart) to measure EAT in patients scheduled for open cardiac surgery. They compared the association between BMI as a measure of obesity and EAT in New Zealand Europeans and in Māori and Pacific people.
"Our results showed that using BMI as a measure of obesity is unlikely to be accurate in Māori and Pacific patients as a way to predict EAT,” said lead researcher, Dr Sean Coffey. "The use of BMI as an indicator for cardiovascular disease risk among Māori and Pacific people may be misleading and contribute to the disparate outcomes among these populations.”
The study included 205 individuals undergoing open heart surgery, 164 New Zealand Europeans (NZE) and 41 Māori/Pacific participants. The EAT was measured using 2D echocardiography.
The mean (SD) age of the study group was 67.9 (10.1) years, 69.1 (9.5) for NZE and 63.5 (11.4) for Māori/Pacific. BMI was 29.6 (5.5) for NZE and 31.8 (6.2) for Māori/Pacific. EAT thickness was 6.2 (2.2) mm and 6.0 (1.8) mm for NZE and Māori/Pacific, respectively. Using univariate linear regression, BMI showed moderate correlation with EAT in NZE (p<0.001); however, there was no significant correlation between BMI and EAT in Māori/Pacific patients (p=0.17). Using multivariate analysis, BMI remained a significant predictor of EAT thickness in NZE (p<0.001).
"The same level of BMI can carry different connotations of risk in different ethnic groups, with BMI likely being an inconsistent measure of obesity in Māori and Pacific patients,” explained Coffey, who added that the findings also build on previously reported differences in body composition between Māori and Pacific people in New Zealand and New Zealand Europeans.