A.M. Adeoye1, O. Adebayo2, M. Nwosu, A. Adebiyi1, M.O. Owolabi 1, B.O. Tayo3, B.L. Salako1,
A. Ogunniyi1, and R.S. Cooper3
1. Department of Medicine, University of Ibadan, Ibadan, Nigeria.
2. Department of Medicine, University College Hospital, Ibadan
3. Dept. of Public Health Sciences, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
Background: Studies differ on which anthropometric measure of adiposity shows good correlation with cardiovascular diseases. In this study, we evaluated the effects of common epidemiological measures of adiposity as a correlate of elevated blood pressure in an African population.
Methodology:The study was carried out between June 2009 and December 2011 at the medical out-patient department of a tertiary healthcare center in Nigeria. Correlation analysis was used to assess the relationship between blood pressure and body mass index (BMI), waist to height ratio (WHtR), and waist circumference (WC).
Results: A total of 1,416 Hypertensives comprising 1090 (77%) adult females recruited over two and half years. Women were significantly older (49.2±8.1 vs. 48.0±10.0 years, p=0.039) and shorter (1.6±6.3 vs 1.7±6.8 meters, p<0.0001) when compared with men. Blood pressure parameters were comparable between women and men. Approximately 1 out of 5 participants had good blood pressure control with no gender difference. Anthropometric measurements showed that 446 (32%) were overweight, 404 (29%) obese and 40 (3%) were morbidly obese. Compared with their male counterparts, females were significantly more likely to be obese (P<0.0001). Similarly, 51.6% of the subjects had abdominal obesity, with female preponderance (P<0.0001). Likewise, a greater proportion of women had substantially higher measured waist circumference risk. Compared with other measures of adiposity, body mass index correlated best with diastolic blood pressure in both gender (P< 0.05).
Conclusion: This study adds to the evidence that obesity is a major cardiovascular risk factor. BMI, as a measure of adiposity, was found to correlate best with blood pressure. These findings support other observations in other populations that BMI rather than waist to height ratio (WHtR), and waist circumference (WC) is a better correlate of hypertension.
The rising trend of increasing adiposity has been a great challenge globally. It has also been increasingly observed that the burden of obesity among Africans is on the increase which is attributable to the epidemiologic transition. In addition, increased adiposity plays major role in all-cause mortality.1 There are abundant evidences that increased adiposity/differential fat distributions are associated with disorders like hypertension, diabetes, and cardiovascular disease.2,3 Body Mass Index (BMI), particularly from about 22kg/m2, although more marked at overweight and obesity level, is associated with the development of hypertension and diabetes mellitus which are major independent risk factors for cardiovascular morbidity and mortality.4,5
BMI, waist-to-hip ratio (WHpR), waist circumference (WC), and waist -to-height ratio (WHtR) are the commonly used epidemiology measures of adiposity.6,7 Other standard direct measurements of viscera and abdominal fat using imaging techniques are not readily available in developing countries and more so, may not be cost effective for large epidemiology studies. BMI is a simple and widely used clinical measure but it is widely believed not to be an optimal indicator of health risk.8 Furthermore, its correlation with adiposity is not consistent across ethnic and racial populations.
Comparing BMI with dual energy xray absorptiometry (DXA), an example of direct measurement of total body fat, the variance for adiposity measurement is very small suggesting reliability of BMI as measure of body fat distributions.9 BMI is more related to body size estimate while WHpR is relevant in differential assessment of fat distribution. Interestingly, WC, WHpR, and WHtR have possibly more predictive power for body adiposity than BMI. 2,10 Waist circumference is an effective and arguably the best inexpensive epidemiologic marker for visceral obesity.11,12 It is also an early predictor of cardiovascular risk development but metabolic risks differed between people of similar WC with different heights.13 Measurement of WC is a practical method which has been shown to be a better predictor of intra-abdominal adipose tissue than BMI and thus provides a measure of fat distribution that cannot be obtained by measuring BMI.14 However, this may not adequately explain the aetiology of hypertension among the obese/overweight.
From the foregoing, despite the availability of several studies that investigated the relationship between measures of adiposity and blood pressure, there is no consensus on which anthropometric measure of adiposity correlate best with blood pressure. Some recent large epidemiological studies may have demonstrated the superiority of WC by showing positive correlations with elevated blood pressure in certain populations.15,16 There is wide variation in the strength of BMI and BP relationship among different population.17 Furthermore it appears that WHtR is better in measuring obesity but it is yet to be determined whether it correlates better than WC with hypertension among Nigeria population.18 In this cross-sectional survey, we assessed which of the measures of adiposity correlates best with blood pressure among Nigerian hypertensives and which can serve as a marker for early identification of individuals at risk and targeted for prevention.
One thousand four hundred and sixteen (1,416) hypertensive patients comprising 1090 (77%) adult female patients were recruited over two and half years (between June 2009 and December 2011). They were enrolled at the medical outpatient department of a tertiary healthcare center in Nigeria.
Inclusion and exclusion criteria
Adult participants aged 18 years and above of both genders that were hypertensive were enrolled into the study. Those that declined participation in the study were excluded.