In this study, hypertension was significantly high among the rural population we studied and is emerging as a public health problem in rural areas. Female sex, older age, ever used alcohol, used much and too much amount of salt, inadequate sleep, and FHH were factors positively and significantly associated with hypertension.
Hypertension in Ethiopia is highly prevalent and accounted for more than half of CVD deaths(20). This study revealed that the overall prevalence of hypertension was 18.5% (95% CI: 16.3, 20.7%). This finding was in agreement with the systematic review and meta-analysis conducted in Ethiopia (18.45%)(29) and a study conducted in Arba Minch Health and Demographic Surveillance Site (17.5%)(56). It’s also similar with findings from other countries: Ombe, Cameroon (19.8%)(57), Davanagere, India (18.3%)(58), South India (18.3%)(59), Southern Rajasthan, India (18.67%)(60), and coastal Karnataka, India (18%)(61). The possible reason for the similarities might be the use of similar age category of the study participants.
On the other hand, our finding was higher than those studies conducted in Amhara regional state, Ethiopia(10%)(62), Humera and Mekelle (15.2%)(63), Southern Ethiopia (9.7%)(64), Gilgel Gibie (7.7%)(65), Nigeria (12.9%)(66), and Rural Uganda (14% and 14.6%)(67, 68). The possible reason for the higher prevalence of hypertension in this study might be the variation in time period between the current study and previous studies which where were conducted between 2008 and 2015. This indicates that hypertension is increasing at alarming rate overtime among the rural adult population in the country.
However, our finding was much lower than those of studies conducted among rural residents of Dabat district, Northwest Ethiopia (25.3%)(32), Mali (21.1%)(69), Nigeria (26.8%)(70), Cameroon (23.9% and 31.1%)(71, 72), and India (32.3%)(73). One possible reason might be the age difference in the study population where the median age of the study participants in those studies conducted in Dabat district, northwest Ethiopia (47 years) and Cameroon (53 years) were higher than this study (40 years). This may overestimate the prevalence of hypertension as evidenced by the older age groups showing higher prevalence(74, 75). The site of BP measurement (inter-arm difference) might also be the possible reason for the higher prevalence of hypertension in those of studies conducted in Mali(69) and Cameroon(72) where the BP were taken on the right arm of the study participants which might result in a difference in BP reading from the left arm as high as 10 mmHg. This is supported by some studies which showed a bias towards higher readings from the right arm than the left arm (76–78).
In this study, a significant association was observed between sex of the participant and hypertension. Females were two times more likely to have hypertension as compared to males. The possible reason might be due to the effect of hormone during menopause which makes the BP more sensitive to salt, which, in turn, lead to higher BP (79). This result was in line with the study conducted in Southern Rajasthan(60). However, studies conducted in urban setting of Ethiopia such as Gondar city(34), Mekelle town(80), Addis Ababa(41, 42, 81), Durame town (38), Hosanna town(36), and Jigjiga city(82) showed males were at risk for hypertension.
Age is a known modifiable risk factor for hypertension where the risk of developing HBP tends to increase as people age increases (83). This study showed that participants’ age was significantly associated with the risk of hypertension. Individuals aged 45-54 years, 55-64 years, and ≥65 years were 4.63, 14.40, and 19.37 times more likely to have hypertension as compared to the age group of 18-24 years, respectively. This was consistent with those studies conducted in Amhara regional state, Ethiopia(62), Dabat HDSS(84), Dabat district and Gondar city(32), Gondar City(33, 34), Northern Ethiopia(63), Addis Ababa(40, 42, 81), Tigray(80), Durame town(38), Wolega(85), Sidama Zone(64, 86), Hawassa University (35), Jimma town (87), Bedele town(88), Dire Dawa city(89), Arba Minch Health and Demographic Surveillance Site(56). Studies conducted in Uganda(68), Cameroon(57, 72), Southern Rajasthan(60), South India(59), India(73), China(90), and urban Varanasi(91) also showed that older age was associated with hypertension. This might be due to the fact that with increasing age, the vascular system becomes less elastic causing the blood vessels to become stiff and less compliant which in turn increases the BP(83).
Moderate to heavy alcohol drinking significantly increases the risk of developing hypertension (92). In this study, the likelihood of hypertension among participants who ever used alcohol was 3.25 times more likely as compared to those who never used alcohol. This was in agreement with those of studies conducted in Dabat HDSS(84), Dabat district and Gondar town(32), Gondar city(34), Addis Ababa(41), Jimma town(87), Wolega(85), Sidama Zone (64, 86), Bale Zone(93), and systematic review and meta-analysis conducted in Ethiopia(29). This finding was also in agreement with those of studies conducted in rural districts of Cameroon(57), Uganda(68), South India(59), and urban Varanasi(91) where individuals who used alcohol were found to be more hypertensive than who never used alcohol. One possible reason might be due to alcohol contains calories which may contribute to unwanted weight gain, a known risk factor for hypertension (94). Secondly, alcohol intake might increase BP by either inhibiting the endothelial nitric oxide syntheses or causing inflammatory injury to the endothelium which in turn decreases the vasodilators in the vascular endothelium(95). The third possible explanations for the association of excess alcohol intake with HBP include stimulation of the renin-angiotensin-aldosterone system, enhanced sympathetic activity, vasoconstriction, and elevated oxidative stress (95–97).
Excessive dietary salt intake is associated with an increased risk for hypertension which in turn a major risk factor for stroke and CVDs, and kidney diseases(44). This study revealed that those participants who used much and too much amount of salt were 2.37 and 3. 78 times more likely to have hypertension as compared to those who used the right amount of salt. Studies conducted in Durame town(38), South India(59), Korea(98), and a systematic review(99) supported this finding where those individuals who used much amount of salt were at risk for hypertension than their counterparts. The reason is explained by the pathophysiological effect of salt/sodium on blood volume; where increased salt consumption provokes water retention, increased blood volume; which in turn leads to a condition of high flow in arterial blood vessels. The other possible reason might be high intake of sodium might damage the endothelial function, changes in the structure and function of large elastic arteries, and modifies the sympathetic activity resulting peripheral vascular resistance and increases in BP(100).
A number of studies have reported that sleep duration might have an important role in the development of hypertension (101, 102). In this study, participants who slept <6 hours per 24 hour (with short sleep duration) were 2 times more likely to develop hypertension as compared to those who slept 6 or more hours over night. This was consistent with the Sleep Heart Health Study (SHHS)(55), study conducted in northeast China among adults aged 18-44 years(103), and meta-analysis(104–108). This might be due to the reason that short sleep durations or sleep deprivation might induce an over activity of the sympathetic nervous system which leads to HBP(109).
Family history of hypertension was found to be a significant factor associated with hypertension. In this study participants with FHH were 2.12 times more likely to have hypertension as compared to their counter parts. This finding was supported by studies conducted in Amhara regional state, Ethiopia(62), Gondar city (33), Dabat district and Gondar town(32), Addis Ababa(40), Sidama Zone(64), Jimma University Specialized Hospital, Southwest Ethiopia(110), Durame town (38), Assosa town(111), Jigjiga city(82), Cameroon(71), Uganda(68), South India(59), and Sri Lankan adults(112). One possible reason might be blood relatives tend to have many of the same genes that can predispose a person to hypertension, heart disease and stroke(113, 114).
This study assessed the magnitude of hypertension and its associated risk factors in rural districts of Northwest Ethiopia where there is limited data and the findings will be eye opening for health authorities, health workers, and researchers. It has used also a standardized tool developed by WHO. However, it was also limited by the tools applied such as assessment of behavioral risk factors using an interview technique which might be liable to recall bias. Furthermore, the study didn’t address the biochemical measurements such as blood lipid and blood glucose level, which are main risk factors for hypertension.