For long, studies have continued to reveal one thing about the incidence of high blood pressure – the fact that the black community is more predisposed to contracting cardiovascular diseases at a rate much higher than their white … counterparts anywhere in the world. In this cover issue, Editor PharmaTimes, MORGAN NWANGUMA examines the question of high blood pressure and hypertension which are the causative factors leading to heart disease and stroke, and how this affects the black population.
According to Dr. Chris C. Amah, the Chief Medical Director of University of Nigeria Teaching Hospital (UNTH), Enugu, the black man or Africans in general suffer most from incidences of heart diseases simply because of the high rate of disease, infection, poverty as well as ignorance on the continent. Numerous studies have confirmed that blacks develop high blood pressure earlier in life, and with much higher blood pressure levels when compared to their white counterparts. Research also discovered that nearly 42% of Black men and more than 45% of Black women aged 20 and older have high blood pressure.
Furthermore, the CMD of UNTH, Enugu said that heart disease affects one or two per cent of the world’s population. While interacting with media reporters during a recent open heart surgery conducted for some 50 children and some adults with heart defects at the teaching Hospital, Dr. Amah said most of the children registered for the open heart surgery at the hospital had congenital heart disease, adding that ignorance and poverty were sometimes at the root cause of some of the problems in developing climes such as Nigeria.
In this regards he emphasised: “That is why we preach that if a woman is pregnant, she shouldn’t swallow all kinds of medicines because even before she knows she is pregnant, any harm would have happened. The heart begins to form from the fourth to sixth week of the pregnancy when the patient wouldn’t even know that she is pregnant, especially those of them that have primary or secondary infertility, and move from one hospital, traditional healer or church to the other, looking for solution.” Yet, there are intrinsic peculiarities which mark out the black man when we consider the issue of cardiovascular health, studies have shown.
Blacks & Heart Disease
Heart failure is a condition in which the heart is unable to adequately pump blood to the body, often resulting in difficulty breathing, fatigue and swelling of the abdomen and/or extremities. Sufferers are often unable to work, walk easily or perform simple daily tasks. From the look of things the black population appears to be more susceptible. Why?
Studies have often shown a strong link between heart disease and stroke; scientists have continued to research into why this two also disproportionately affect blacks. So many questions are being raised. Clyde W. Yancy, MD, is associate dean of clinical affairs and medical director for heart failure/transplantation at the University of Texas Southwestern Medical Centre; he says the inherent factors make blacks more vulnerable to all forms of cardiovascular ailments.
“What sets the stage for the more aggressive and higher incidence of heart disease in blacks is a very high incidence of high blood pressure,” Yancy says. “This predisposes blacks to more heart disease, kidney disease, stroke and heart failure.”
Meanwhile, clinical trials confirm that blacks and whites react in different ways towards high blood pressure therapies. For this reason, existing guidelines for treating patients recommend that physicians consider different drugs in treating patients depending on their race. True enough, Yancy says that a closer look at the data shows that race tends to be a marker for more complicated high blood pressure treatment.
“Data suggests that all therapies do equally well — but patients at higher risk need more intensive therapy,” he says. A similar situation exists for heart failure. A promising treatment for heart failure didn’t seem to be working — until researchers noticed that it worked much better for black patients than for white patients. A study of black patients confirmed this finding — and provided tantalising evidence that the drug will help patients of all races with certain disease characteristics.
Whether on the African continent or in relation to Africans (blacks) in the diasporas, research have time after time reported a higher prevalence of hypertension in blacks than in whites, a main reason for the higher incidence of cardiovascular disease in blacks. But going by the long list of presumed factors responsible for this higher prevalence puts experts at a quandary as to the real reasons for this phenomenon.
Causes and reasons for disparities
Biological differences in the mechanisms of blood pressure control or in the environment and habits of whites and blacks are among the potential causes, according to experts. Yancy says that apart from some unique cultural issues, “Genes definitely play a role; so does the environment in which people live, socioeconomic status — and, yes, racism.”
The higher prevalence of hypertension in blacks living in the United States instead of Africa demonstrates for example, that environmental and behavioural characteristics are the more likely reasons for the higher prevalence in blacks living in the United States. They could act directly or by triggering mechanisms of blood pressure increase that are dormant in blacks living in Africa, experts say.
Two renowned authorities and authors of best-selling clinical reference on hypertension, Kaplan and Victor listed 18 genotypes and intermediate phenotypes that were implicated with an increase of blood pressure in blacks. A higher sensitivity to alcohol could be added to that list. Some of these mechanisms, such as a higher renal retention of sodium by blacks, are attractive. The “slavery hypertension hypothesis” states that the higher prevalence of hypertension among blacks could have resulted from an enhanced ability to conserve salt by slaves, protecting them from fatal salt-depletive diseases during the stormy Atlantic passage, such as diarrhoea and vomiting.
This condition would bring on hypertension when they and their descendants consumed the much higher sodium content in American compared with African foods. But this hypothesis is still difficult to prove or disprove. Looking at Yancy’s statement relating to the role of genes and the environment, research experts tend to generally agree that therein lies the answer to this enigma. The association between genetic traits and renal outcomes has been reported in black Americans versus white Americans. Kao et al and Kopp et al reported an association between a genetic variation of the MYH9 region on chromosome 22 with focal segmental glomerulosclerosis, a condition previously attributed to “hypertensive nephrosclerosis” and found much more frequently in black patients with end-stage renal disease than in whites with end-stage renal disease.
The dietary angle and the environment
Also, there is the strict dietary angle to all this. In terms of dietary behaviour especially, it tends to be even a more crucial factor. Looking at the resultant effects of differential dietary habits, excess adiposity emerges as a natural candidate to explain the higher prevalence of hypertension in blacks, who have a 51% greater prevalence of obesity than whites. Nevertheless, excess of adiposity does not fully account for the higher prevalence of hypertension in blacks. This also is evident from the report of the American National Health and Nutrition Examination Survey (NHANES) III. Drawing inference from it Okosun et al showed clearly that the population-attributable fraction of hypertension attributed to abdominal obesity was 24.9% in black men and 15.9% in black women.
The risk of black ethnicity for hypertension persisted after adjustment for abdominal obesity and other confounders: the odds ratios in black men were 1.80 (95% CI: 1.54 to 2.11) and in black women 2.70 (95% CI: 2.07 to 3.28). There is no conclusive evidence that other nutritional factors could explain the higher prevalence of hypertension in blacks. Yet there does not seem to be any conclusive evidence that nutrition has a major hand here. Looking at the NHANES report 2003–2006, nutrients were identified by just one 24-hour dietary recall.
In a recent study carried out among Americans and published in the New England Journal of Medicine, the signs showed that the blacks in the community suffer heart failure at a rate that is 20 times above their white counterparts, CNN reported. The study found that the heart failure rates for African-Americans in their 30s and 40s are the same as rates among white patients in their 50s and 60s. Findings by the researchers as well discovered that one in 100 black men and women could develop heart failure before age 50.
Victims of heart failure are usually not able to work, walk normally or carry out simple daily routine. Sharing her experiences, Dr. Kirsten Bibbins-Domingo — an internist and the study’s lead researcher — doctors who care for large populations of black patients, observes that those patients suffer from heart failure at a rate higher than the white patients with whom they live. She said to CNN, “However, this study is the first to highlight just exactly how high those rates are.”
Bibbins-Domingo and her team found that the risk factors for heart failure were already present when patients were in their 20s, thereby raising the likelihood they would have heart failure two decades later. The primary explanation behind the disparity across race lines is high blood pressure, heart experts say. “The burden of hypertension is extraordinary. It is a statement of fact that the incidence of high blood pressure is higher in African-Americans than non-African-Americans,” explains Dr. Clyde Yancy, cardiologist and spokesman for the American Heart Association.
There appears to be several possible reasons blacks experience high blood pressure at such young ages. According to Yancy, who wrote an editorial on this topic published alongside the study, family history plays a major role because hypertension tends to run in families. But environment is also key, he says, adding that specifically, the high incidence of obesity, especially among black women, raises the risk of having high blood pressure.
“Some communities (of African-Americans) have as many as 40 percent of women who are obese,” he points out. Stress and the high incidence of diabetes are additional confounding factors. In one of such studies, failure was diagnosed in 27 test subjects; all but one, were black. Whereas heart failure is most commonly known as a disease of the elderly, most of the study participants with heart failure were in their 30s and 40s.
Yancy underscores the life-threatening significance of these findings. “Once you have heart failure, the outcomes change dramatically,” he says. “If someone is diagnosed with heart failure at age 30, then even if we’re talking about a 10-year life expectancy, they would be dead by age 40.”
What we can do
Doctors and scientists refer to the research findings as an obvious warning signal that blacks must therefore be screened early enough, more regularly and with greater sensitivity for high blood pressure. Yet, while making sure of the above it must not be lost on us that there still remains the fact that critical barriers to accessing medical care and the crisis of dealing with fake and adulterated medicines remain with us especially here in Africa. Thus the body of pharmacists – the Pharmaceutical Society of Nigeria (PSN) in unison with the National Agency for Food and Drug Administration and Control (NAFDAC) must effectively join forces to arrest the situation.
It becomes pertinent then that the maxim, ‘prevention is better than cure’ be sounded more loudly. Also, it will be foolhardy for anyone to want to rely on medical care alone in order to live above cardiovascular diseases. As such, whether one is diagnosed with any form of cardiovascular disease or not, beyond your doctor’s orders, you will do well to embark on specific lifestyle changes.
These are likely to involve proper lifestyle intervention measures like taking to exercise; ensure that your weight is controlled to a normal range, as well as consuming less salt in your foods. And of course, if already acquired conditions refuse to go away, experts advise that you can make use of your medications to bring your blood pressure under control. In the first place Yancy says, “We must do whatever we can to prevent heart failure from developing.” The reason for this he adds is simply “Because the best treatment for heart failure is to never allow it to happen in the first place.”