Abstract
Background: Hypertension is the leading risk factor for death and disability globally. Its prevalence is increasing worldwide especially in low and middle income countries. It is considered a silent killer because it has no specific symptoms and thus can go unnoticed for many years, only presenting for the first time with serious complications. The situation of undiagnosed hypertension in Sudan has not been fully investigated before. Objective: To determine the prevalence of undiagnosed hypertension in the rural communities of River Nile State (RNS), Sudan and to assess the associated risk factors. Methods: A cross-sectional community-based study, in which 1099 volunteer adult participants from the rural communities in RNS, not known to be hypertensive, were included. Blood pressure was measured as well as anthropometric measurements. The WHO stepwise approach for non-communicable diseases surveillance was used for data collection. A p value below 0.05 was considered statistically significant. Results: There were 461 males (41.9%) and 683 females (58.1%). The male to female ratio was 1:1.4. The age range was 18–90 years, with a mean age of 39.6 (STD ± 15.9). The prevalence of undiagnosed hypertension was 38.2%, with a prevalence of 36.7% among males and 39.3% among females. There were significant associations between undiagnosed hypertension and increasing age, obesity, illiteracy and diabetes mellitus (p < 0.05). Conclusion: This study uncovers a hidden epidemic of a silent killer in the rural communities of RNS. Urgent interventions are required to address this serious health epidemic.
Introduction
Worldwide, hypertension is the number one cause of death and is ranked number four in disability adjusted life years (DALY).Citation1 It constitutes a public health epidemicCitation2–4 with an increasing global prevalence, especially in low and middle income countries.Citation3
In sub-Saharan Africa, the burden of hypertension has been increasing continuously,Citation5,Citation6 with prevalence varying widely between 15% and 70%.Citation7
In Sudan, the prevalence of hypertension is rising.Citation8–10 The increasing prevalence of hypertension is attributed to population growth, ageing, unhealthy diets, lack of physical exercise, obesity and increasing life stresses.Citation2
As it has a silent nature, early identification of subjects with undiagnosed hypertension may prevent or reduce progression of many of its serious complications, including stroke, ischemic heart disease, congestive cardiac failure, sudden cardiac death, peripheral vascular disease and renal insufficiency.Citation2,Citation11–13 The aim of this study was to determine the prevalence of undiagnosed hypertension in a rural community in River Nile State (RNS), and to identify some of the risk factors associated with the development of hypertension.
Patients and methods
Study design
A descriptive cross-sectional community-based study was conducted as a house-to-house survey in May 2013.
Settings
RNS lies in north Sudan, bordering the capital city Khartoum and extending to the northern border with Egypt, with an area of 124,000 m2. The total state population is about 1,250,000, with residents of different ethnic backgrounds, albeit with a predominance of the Ja'alin tribes; the majority is farmers living in rural areas. There are six cities and about 350 villages in RNS, with similar demographic characteristics.
Study population, sampling technique and sample size
A multi-stage cluster selection technique was used, for villages in RNS and for participants. Thirty-five villages were randomly selected from the different localities proportional to the number of villages in each locality. Then, in the selected villages, all eligible adults who volunteered to participate were surveyed in a house-to-house basis. The total number of participants was 1099. The estimated population of the selected villages is about 100,000.
Exclusion criteria
Individuals previously diagnosed as having hypertension or currently taking anti-hypertension medications, those below 18 years and pregnant women were excluded.
Data collection
The World Health Organization (WHO) stepwise approach for non-communicable diseases surveillance was used for data collection. The approach had three steps: a questionnaire to gather demographic and behavioral information, physical measurements, including anthropometric measurements and blood pressure and biochemical tests.Citation14
Each participant was questioned for demographic data, past medical history, risk factors and family history of hypertension. Data were collected through an interviewer administered pre-tested questionnaire.
Anthropometric measurements
Anthropometric measurements were taken using standardized technique and calibrated equipment. Body mass index (BMI) was calculated using the following formula: weight in kilograms divided by height in meters squared. BMI was defined according to the following categories: < 18.5 kg/m2 underweight, 18.5–24.9 kg/m2 normal, 25–29.9 kg/m2 overweight and >30 kg/m2 obese.Citation15
Blood glucose measurement
Capillary blood was obtained through a finger prick technique, after sterilization by alcohol. Random blood samples were tested for glucose level using a Glucometer (Accu-Check Active®, Roche Diagnostic, Mannheim, Germany). Diagnosis of diabetes was based on the American Diabetes Association 2003 criteria.Citation16 An individual with a random blood sugar (RBS) ≥ 200 mg/dL (11.1 mmol/L) was considered diabetic. Fasting blood glucose (FBS) tests were done at 8:00 am, with 8–10 h overnight fasting for those who had RBS of 170 mg/dL (9.4 mmol/L) or more. Any individual with FBS ≥126 mg/dL (7 mmol/L) or more was considered diabetic. Individuals with RBS between 170 and 199 mg/dL (9.4–11 mmol/L) or FBS between 110 and 125 mg/dL (6.1–6.9 mmol/L) were considered as cases of impaired glucose tolerance (IGT).
Blood pressure measurement
Blood pressure was measured with the patient in the sitting position using a calibrated portable mercury sphygmomanometer, with appropriate cuff size. The average of three readings was recorded, with each taken after five minutes rest. Blood pressure levels were classified according to the criteria of the seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure.Citation17
Normal blood pressure = a systolic blood pressure less than 120 mmHg and a diastolic blood pressure less than 80.
Prehypertension = a systolic blood pressure between 120 and 139 mmHg and a diastolic blood pressure between 80 and 89.
Stage 1 hypertension systolic blood pressure between 140--159 and diastolic blood pressure 90--99. Stage 2 hypertension is more than or equal to 160/100.
Quality assurance
House-to-house data collection was performed by trained field workers. The field study team was composed of medical students, laboratory technicians and physicians. All were trained by the principle investigator for three days on the study procedures.
Statistical analysis
The data generated were coded, validated and analyzed using the program Statistical Package for Social Science (SPSS) version 20 (IBM Statistics, Chicago, IL). A Pearson Chi squared test was used to test for significance between proportions. p Value below 0.05 was considered statistically significant. The main variables analyzed were age, sex, BMI, blood pressure, blood glucose level and a family history of hypertension.
Ethical approval
Verbal consent was obtained from each participant prior to enrollment. The following information was given during data collection to ensure participants had the information needed to make informed consent: the participation was optional, there would be no penalty for refusal, a complete description of the aims of the study, potential benefits and risks and assurance of confidentiality of any information given. Any other additional information requested by participants was provided during data collection. Individuals found to have high blood pressure, high blood glucose or any other medical condition were referred with their permission to a physician for further evaluation. All information obtained was kept confidential. All patients who attended the physicians' clinic at the time of study were offered investigations and medications free of charge to ensure that participants did not acquire additional financial burdens. An ethical clearance of the research was obtained from the Ethical Committee of the Faculty of Medicine, Nile Valley University.
Results
Sociodemographic variables
In this study of 1099 individuals, 461 (41.9%) were males and 683 (58.1%) were females, for a male to female ratio of 1:1.4. The age of the study participants ranges from 18 to above 90 years, with a mean age of 39.6(±15.9) years. Overall, a larger proportion of the study participants were below 45 years of age. An education profile of the participants showed that most have a primary educational level.
Regarding BMI, a higher number of participants have a normal weight; 504 (46.4%).
About one-third of participants, 387 (35.2%) have a family history of hypertension, while 103 (9.4%) have diabetes mellitus. General characteristics of the study population are presented in .
Table 1. Demographic characteristics of the study population, RNS, Sudan 2013 (n = 1099).
Prevalence of undiagnosed hypertension and its relation to sociodemographic and risk factors
Overall prevalence of undiagnosed hypertension is 38.2%. Females were found to have a slightly higher prevalence than males (39.3%, 36.7% respectively) (p less than 0.01).
There is an increasing trend in the prevalence of undiagnosed hypertension with age: the lowest undiagnosed hypertension prevalence was detected among those 18–25 years of age, and the highest prevalence was recorded for participants above 65 years.
Regarding educational status, a higher prevalence rate was observed in subjects who are illiterate. Regarding occupational types, the highest prevalence rate was recorded in retired individuals, followed by farmers.
With regard to BMI, increasing prevalence of undiagnosed hypertension was observed with increasing weight. Participants with diabetes were observed to have a prevalence of undiagnosed hypertension of 57.3%. Associations between undiagnosed hypertension and risk factors are shown in .
Table 2. Relation between undiagnosed hypertension and risk factors, RNS, Sudan 2013 (n = 1099).
Discussion
The prevalence of undiagnosed hypertension in this study is 38.2%. This is comparable to a prevalence of 39.6% found in a similar study conducted in rural areas of Northern state, Sudan,Citation10 in the US (39.4%),Citation18 and interestingly, similar to that previously recorded among Nuba and Coptic ethnic groups inhabiting RNS.Citation19 This prevalence is higher than the rates recorded in India (22.2%)Citation20 and lower than those found in Ghana (83%).Citation21
The high prevalence of undiagnosed hypertension in this study could be attributed to a variety of factors, including but not limited to: increasing urbanization, dietary changes, increasing life stress and possibly to some genetic factors.
With regard to the sex distribution of undiagnosed hypertension, females show a slightly higher rate of undiagnosed hypertension than males, this is similar to the result disclosed by some authors.Citation9,Citation22 Male predominance, however, is reported in many studies.Citation23–25 It is likely that the slight difference observed in this study could be due to lower participation among males, in addition, it might be due to the presence of coexisting risk factors in females.
Different studies have reported that the prevalence of hypertension increases with age. In the current study also an increasing trend in the prevalence of undiagnosed hypertension with age was observed. This finding is consistent with most study findings on the prevalence of hypertension in populations.Citation9,Citation21,Citation23
The study found a higher prevalence of undiagnosed hypertension in illiterates and subjects with low educational levels. This finding is consistent with what has been observed by many authors.Citation24,Citation26 Some studies, however, have reported the opposite – that higher educational level was associated with hypertension.Citation27 In general, a low educational level could be associated with lack of patient awareness and reduced health-seeking behavior. A significant association was found between BMI and undiagnosed hypertension. This finding is consistent with what has been documented by many other studies.Citation21,Citation27
The current study does not find a significant association between undiagnosed hypertension and a family history of hypertension. On the contrary, significant and positive association between family history of hypertension and hypertension occurrence was reported in other studies.Citation9,Citation10,Citation20 The lack of association in this study might be attributable to participants' ignorance of the hypertension status of their parents and families.
Consistent with the findings of many studies,Citation28–30 our study revealed a significant association between diabetes and hypertension. This suggests either shared genetic or environmental factors in the etiology.Citation29,Citation30 This implies that screening for hypertension needs to be targeted at diabetic patients.
This study is not without limitations. The cross-sectional design may not allow for generalization of the results to the whole population; in addition, the role of diet and physical activity on the prevalence of undiagnosed hypertension was not investigated, owing to the complexities involved in measuring such parameters. The interval of blood pressure measurement, i.e., five minutes apart, is another limitation. However, in such surveys it is impractical to find the same individuals for blood pressure measurement if the interval between measurements is too long.
Despite these limitations, this study is novel and is the first one to uncover the situation of hypertension in RNS. Based on these findings, we anticipate that the prevalence of hypertension will increase in RNS over the coming years, since all the identified predisposing risk factors are becoming more and more common.
In conclusion, this study identified 38.2% prevalence of undiagnosed hypertension among the rural population of RNS. It should be noted that this result is alarming. In addition, it indicates that there might be a large number of people who have hypertension but are not aware of it. Moreover, it was observed that undiagnosed hypertension existed in all age groups, indicating vulnerability of the whole population, not just a specific segment.
Targeting the prevention of the modifiable risk factors might reduce the prevalence of undiagnosed hypertension. Additionally, regular screening for hypertension in individuals above 35 years, those with high BMI and/or those with a history of diabetes, will bring more unknown cases to medical attention. In addition, this study recommends further large-scale community-based studies to formulate guidelines and also calls for the creation of a public health policy designed to reduce the potentially devastating outcomes of undiagnosed hypertension.
Declaration of interest
All authors declare no conflict of interest.
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