Cardiovascular Diseases (CVDs), a group of disorders that affect the heart and/or blood vessels are the leading causes of deaths and disability-adjusted life-years (DALYs) globally. In 2017, CVDs were responsible for an estimated 17.8 million deaths, with more than 80% occurring in low- and middle-income countries (LMICs). LMICs are experiencing a higher burden of CVD deaths due to rapid urbanization, aging, and health and nutrition transitions. It is projected that by the year 2030, CVDs will cause more than 23.6 million deaths with stroke and coronary heart diseases being the main contributors if no appropriate measures are taken to alleviate the problem .
Tanzania, like other developing countries, is also facing a higher burden of CVDs. CVDs alone account for 13% of the total deaths caused by non-communicable diseases in Tanzania with adults aged 25–64 years being affected the most . Age-standardized mortality rates attributed to CVDs were reported to be higher among Tanzanian men compared to women (473 versus 382 per 10,000 population) .
Trends of CVD death rates in SSA, including Tanzania, are highly driven by lifestyle changes, characterized by low levels of physical activity, excessive alcohol consumption, tobacco use and unhealthy eating. Poor management of these factors has resulted in intermediate risk factors such as raised blood pressure, raised blood cholesterol, diabetes, overweight and obesity, that have direct linkage with CVDs. All these factors occur as a result of rapid urbanization, modernization, socio-economic status and increased advertisement of the Westernized food market .
Despite the rising prevalence of CVDs in Tanzania, knowledge about their risk factors and warning signs in the Tanzanian general population is generally low, especially among individuals from rural areas. However, even those with adequate knowledge of CVDs are subjected to the risk of developing them due to disparity between their health literacy and lifestyle choices .
5 Most Common Cardiovascular Diseases
- Heart Attack
A heart attack, also known as myocardial infarction, refers to death or permanent damage of an area of the heart muscle which occurs when it is cut off from the oxygen it needs to operate. It is a medical emergency which happens because the blood flow delivering that oxygen has been significantly reduced or stops entirely. This is due to atherosclerosis, or the slow buildup of plaque, which includes fat, cholesterol, and other substances, in the coronary arteries. Blood clots can then form around the plaque, which tend to slow or block the blood flow and cause a heart attack. A heart attack may be severe enough to cause death or it may be silent.
Stroke is considered a heart disease because the condition centers around blood flow. However, a stroke is due to problems with blood flow to the brain rather than the heart. Ischemic strokes account for 87 percent of all strokes and occur because of blockage in a blood vessel that delivers blood and oxygen to the brain. Without blood and oxygen, parts of the brain can suffer damage or die off if not treated quickly. Hemorrhagic strokes make up about 13% of stroke cases and occur when weakened blood vessels in the brain rupture or burst resulting in bleeding in the brain. When blood accumulates in the tissue around the rupture, it puts pressure on brain cells and damages them. Hemorrhagic strokes may have various causes such as a vascular malformation or abnormal growth of brain blood vessels.
- Heart Failure
Heart failure, also called congestive heart failure, refers to the heart not pumping blood as well as it should. It does not mean the heart has stopped beating entirely, as the name might suggest. The heart continues to pump blood, but not at a high enough rate for the body to continue to function. The fatigue and shortness of breath that can result from untreated heart failure can greatly interfere with everyday activities like walking or climbing stairs.
A heart arrhythmia is any abnormal rhythm of the heart: too slow, too fast, or at an irregular beat or tempo. Without proper rhythm, the heart doesn’t work as effectively. The heart may not be able to pump enough blood to deliver oxygen and nutrients to other organs.
- Heart Valve Complications
Like arrhythmias, heart valve complications can cover a variety of different abnormalities. Stenosis means the valves in the heart don’t open enough to allow blood to flow through normally. Regurgitation occurs when the heart valves do not close correctly, which enables blood to leak through. Like the arteries in your heart, the heart valves also need to operate properly to stave off life-changing complications .
Risk factors for CVDs fall into three broad categories: intermediate, modifiable/behavioural, and non-modifiable as illustrated in the schematic below .
Intermediate risk factors
Intermediate risk factors are health/medical conditions that appear as a result of uncontrolled behavioral risk factors. Key intermediate risk factors for CVDs include raised blood pressure (hypertension), diabetes, raised blood cholesterol, and overweight and obesity.
Uncontrolled blood pressure can result in more health complications, including CVDs such as myocardial infarction, aneurysms, and stroke and other heart diseases. According to the 2014 WHO country profile report for non-communicable diseases (NCDs), approximately 31.6% of men and 29.4% of women in Tanzania were hypertensive. Moreover, there is a rapid increase in prevalence of hypertension in Tanzania, with significant variation between rural and urban settings that is characterized by sedentary lifestyles, urbanization and aging population. Results from prospective observational study conducted at the Cardiovascular Center of Muhimbili National Hospital in Dar es Salaam showed that, 45% of the heart failure patients were hypertensive. Despite a higher prevalence of hypertension in different areas of Tanzania, many people are not aware of the related risk factors, with low rate of diagnosis and treatment .
It is known that raised blood cholesterol is a common risk factor for CVDs, including ischemic heart diseases, stroke and heart failure. Prevalence of raised blood cholesterol is influenced by sedentary lifestyles and rapid urbanization. Furthermore, poor dietary diversification contributes to increased blood cholesterol. Lower intake of fruits and vegetables and higher intake of red meat have been linked to increased levels of blood cholesterol. Nearly 20% of males and 24% of females in Tanzania had high blood cholesterol >5 mmol/L according to WHO estimates in 2010. Kilimanjaro region have been reported with highest prevalence of raised cholesterol (17.4% of men and 19% of women) compared to other regions of Tanzania like Morogoro (5% of men and 6.7% of women) and Mara (4.8% of men and 6.9% of women) .
Diabetes is a prime risk factor for cardiovascular disease (CVD). Vascular disorders include retinopathy and nephropathy, peripheral vascular disease (PVD), stroke, and coronary artery disease (CAD). Diabetes also affects the heart muscle, causing both systolic and diastolic heart failure. According to 2017 International Diabetes Federation estimates, more than 1.7 million people living in Sub-Saharan region are diabetic and Tanzania has been mentioned as among the country with the highest prevalence of diabetes. Results from the 2012 national survey showed that more than 9% (8% of men and 10% of women) of adult population aged ≥25 years were diabetic. Higher prevalence of diabetes is highly driven by rapid urbanization, sedentary lifestyles, and nutrition transition, which tend to promote overweightness and obesity .
Lack of diabetes guidelines, screening tools, poor reporting system, inadequate drug therapy and lack of training among healthcare providers and beneficiaries have been found to be potential reasons as to why many dispensaries and healthcare centers fail to provide valuable diabetic care in Tanzania. All these lead to the increased diabetic complications including angina, myocardial infarction, stroke, peripheral artery disease, and congestive heart failure. Despite the growing trends of diabetes in Tanzania, still there is low rate of awareness on diabetes and its complications in the population .
Overweight and obesity are defined as a body mass index of ≥24.9 and ≥29.9 kg/m2, respectively. The likelihood of chronic diseases such as diabetes, hypertension, as well as CVDs including coronary artery disease and and stroke, increases with increased body mass index (BMI ≥24.9 kg/m2). Both socio-demographic characteristics and economic factors influence occurrence of overweight and obesity in the population. However, lack of enough statistics, together with socio-cultural beliefs, create greater challenges in understanding the trends of overweight and obesity as public health challenges in African countries, including Tanzania. Findings from multi-country cross-sectional study conducted in 2016 in four SSA countries showed higher prevalence of overweight and obesity of 46% in rural Uganda, 48% in peri-urban Uganda, 68% in urban Nigeria, 75% in urban Tanzania and 85% in urban South Africa. Prevalence of overweight and obesity are still increasing in Tanzania as reported in the STEPwise survey conducted in the country in 2012, which showed 26% of the adult population aged >25–64 years were overweight and obese, with women being more affected than men (37% of women versus 15% of men). Few studies conducted in the country, especially in urban Der es Salaam, showed higher prevalence of overweight and obesity among school-age children. For example, a study by Mpembeni and colleagues reported the prevalence of overweight and obesity of 15% (10.1% boys and 19.4% girls) among primary school children in Dar es Salaam, Tanzania .
Modifiable/behavioral risk factors are most common preventable risk factors that underlie the development of CVDs. These include unhealthy eating, tobacco use, excessive alcohol intake, and physical inactivity. Poor management and prevention of these risk factors leads to metabolic/physiological changes that accelerate the development of CVDs.
- Alcohol use
Alcohol consumption has been associated with increased risk of developing CVDs including atrial fibrillation (an abnormal cardiac rhythm), cardiomyopathy, acute myocardial infarction, hemorrhagic stroke, and ischemic stroke as it promotes raised blood cholesterol, high blood pressure, platelet coagulation and increased fibrinolysis. In 2012, prevalence of alcohol consumption among men and women in Tanzania were reported to range from 23–38% and 13–13%, respectively. Further results showed that 29.4% (38.3% men and 20.9% women) of the adult population were current alcohol users. Among them, 27.4% of men and 13.4% of women were binge drinkers. Moreover, 17.2% of adults aged 15–59 years were reported as current alcohol users in urban settings, and this was associated with socio-economic status of urban dwellers. Some of the chronic diseases such as hypertension, and diabetes are increasing in Tanzania due to the high number of alcohol drinkers. Higher prevalence of hypertension (50%) was reported among alcohol users compared to non-alcohol users (49.3%) in a study conducted in Mafia Island. Furthermore, alcohol consumption was related to increased CVD risk factors, such as diabetes (9.8%) hypertension (53.3%), overweight and obesity (73.3%) among study participants .
- Unhealthy diets
Diet plays an essential role in the etiology and pathophysiology of different CVDs. Diet and nutrition have been recognized as major contributors atherosclerotic plaque formation and development of CVDs, including coronary heart disease and stroke. Unhealthy diet is linked to other CVD risk factors such as high blood pressure, elevated blood cholesterol, diabetes, overweight and obesity. According to a subnational STEP survey conducted by WHO in 2012, only 9.2% of individuals aged 25–64 years in Tanzania consumed at least less than 5 servings of fruits or vegetables on average per day. A study conducted in peri-urban Tanzania revealed the association between use of palm oil as cooking oil, inadequate consumption of fruits and vegetables and high intake of meat with increased blood cholesterol. Higher prevalence of hypertension in urban areas, especially among women, has been related to higher consumption of meat and coconut oils. Moreover, higher consumption of protein-rich foods, particularly meat, milk and blood with an inadequate intake of fruits and vegetables were associated with increased risk of hypertension among Maasai living in Simanjiro district. Higher consumption of highly processed foods, dietary salt with low levels of physical activity, and low knowledge of dietary choices were associated with increased prevalence of hypertension in different settings of Tanzania .
- Physical inactivity
People who do not engage in regular exercise or physical activity are more likely to have hypertension, high blood cholesterol and be overweight or obese. In Tanzania, low levels of physical activity have been associated with increased body weight, diabetes, unfavorable lipid patterns and other CVD risk factors in rural and urban settings. Urban settings represent lower levels of physical activity compared to rural areas, which might be due to sedentary lifestyles adopted by urban dwellers as opposed to manual activities performed by rural dwellers. Therefore, the urban population in Tanzania faces a higher incidence of overweight, obesity, and elevated blood cholesterol levels than the rural population. A prospective cohort study conducted in Tanzania showed that migration from rural to urban areas reduced the level of physical activity by 52.9% (79.4% to 26.5%) in men and 21.9% (37.8% to 15.6%) in women .
- Tobacco use
Smoking is a major contributor of CVDs as it can potentially cause atherosclerosis and raise blood pressure. Currently, there is no much information concerning the use of tobacco in Tanzania, however, few studies have documented higher incidence of tobacco use among men and women. In 2018, the prevalence of smoking in Tanzania was 13.30%, a 0.8% decline from 2016 . This refers to the percentage of men and women aged 15 and over who currently smoke any form of tobacco product including including cigarettes, cigars, and pipes, and excluding smokeless tobacco on a daily or non-daily basis. The rates are age-standardized. Additionally, the prevalence of hypertension was observed to be higher (52%) among smokers compared to non-smoker (26.1%) in a study conducted in Dar es Salaam .
Non-modifiable risk factors
Non-modifiable risk factors are factors that cannot be changed which include age, sex, race or ethnicity, and family history. The more of these risk factors you have, the greater your chance of developing CVDs.
- Increasing Age. The majority of people who die of coronary heart disease are 65 or older. While heart attacks can strike people of both sexes in old age, women are at greater risk of dying (within a few weeks).
- Male gender. Men have a greater risk of heart attack than women do, and men have attacks earlier in life. Even after women reach the age of menopause, when women’s death rate from heart disease increases, women’s risk for heart attack is less than that for men.
- Heredity (including race/ethnicity). Children of parents with heart disease are more likely to develop heart disease themselves. African-Americans have more severe high blood pressure than Caucasians, and a higher risk of heart disease. Most people with a significant family history of heart disease have one or more other risk factors. Just as you can’t control your age, sex and race, you can’t control your family history. So, it’s even more important to treat and control any other modifiable risk factors you have .
Tanzania is experiencing rapid growth of modifiable and intermediate risk factors that accelerate CVD mortality and morbidity rates. In both rural and urban settings, cardiovascular risk factors such as tobacco use, excessive alcohol consumption, unhealthy diet, hypertension, diabetes, hyperlipidemia (high level of cholesterol or triglycerides in blood), overweight, and obesity, are documented to be higher. Increased urbanization, lifestyle changes, lack of awareness and rural to urban movement have been found to increase CVD risk factors in Tanzania. Despite the identification of modifiable risk factors for CVDs, there is still limited information on physical inactivity and eating habits among the Tanzanian population that needs to be addressed .