Algeria has been the focus of extensive national and international research on evaluating the burden of NCD risk factors in the context of the epidemiological transition study and its impact on health systems in North Africa. In a 2014 WHO report on Algeria, NCDs were associated to 77% of death causes, with CVD accounting for the majority (41%) .
Prehypertension and hypertension are the most frequent cardiovascular disorders worldwide, and they are increasingly regarded as one of the most serious public health issues, particularly in developing nations .
This study was conducted on a representative sample of 6765 adults using data from the Algerian STEPwise survey 2016–2017 to assess and determine the prevalence of prehypertension and hypertension as well as the risk factors in Algeria.
The results showed that prevalence of prehypertension was high in the Algerian population, with a rate of 36.2%, affecting more males than females (43.2% vs 30.8%). As a result, preventive measures should be adopted with patients who have been diagnosed as prehypertensive, such as monitoring their blood pressure more closely, because a considerable proportion of them are at risk of developing hypertension .
Being an under-studied disease in Maghreb countries, prehypertension had a prevalence of 36.2%, which is identical to that found in a cross-sectional survey conducted in Algiers recently which estimated the rate of prehypertension at 36.7% (49.5% in men, against 31.4% in women) .
The findings of that study also corresponded to the rate of the adult population in north-east China (36.0%)  and the adult population of Brazil (36.1%) . However, it was lower than the rate of Bangladesh’s population aged 25 to 45 years (41.8%) , and still slightly higher than the adult population of southern Iran (33.7%)  and Taiwanese adults (34%) .
Furthermore, the results indicated that the overall prevalence of hypertension in our study was 31.6%, of which 13.0% were newly detected at the time of the study evaluation; i.e., a rate of 41.1% of Algerian participants living with undiagnosed hypertension. The latter may have a higher risk of complications, which would then be too late to avoid.
In comparison to national and regional studies, this proportion of hypertension is consistent with that found in most Algerian populations, which ranges from 30 to 40% [13, 15,16,17]. It is higher than in some previous studies. The STEPSwise survey in Algeria in 2003 found a BP rate of 26 ± 2.6% . A level of 24.9% was also found in a TAHINA research conducted in 2005 . However, it was still significantly lower than the North African multicenter study conducted in 2013 with a very high hypertension’s proportion of about 45.4% , as well as the “Africa / Middle East Cardiovascular Epidemiological” study conducted in 2018 with an estimated hypertension rate of 39.5% for the subgroup “Algeria” .
In addition, the prevalence of hypertension in this study was comparable to the overall prevalence in sub-Saharan Africa, which was estimated at 30% , as well as Tunisia’s prevalence of 30.6% , and higher than the global adult population’s prevalence of 26.4%, Sudan’s prevalence of 27.6% , Palestine’s prevalence of 27.6% , and Canada’s prevalence of 27% .
On the other hand, it was judged to be significantly lower than in Morocco (39.8% ), Oman (41.5% ), and European countries (38% in Sweden, 42% in England, 47% in Spain, 55% in Germany) .
Furthermore, the prevalence of prehypertension in both sexes decreased in the older age groups from 30–44 years, according to our results. However, in both sexes, the prevalence of hypertension rose with age, which is in line with the findings of other research [34, 35].
Algeria has seen an epidemiological transition as a result of ageing combined with changes in lifestyle, particularly dietary and behavioral patterns. These had a significant impact on risk factors as well as on the incidence of cardiovascular morbidities, diabetes and obesity .
Although the bivariate analysis showed a significant correlation between the prevalence of the prehypertension/hypertension groups according to the categories of gender, age, marital status, education level, locality, occupation, BMI (overweight and obesity), AO, smoking status, diabetes, and hypercholesterolemia, the multivariate analysis using logistic regression retained only some determinants with a significant influence on the prevalence of prehypertension and hypertension.
It revealed a highly significant relationship between the chance of acquiring prehypertension and hypertension as one gets older. These results are in line with previous publications from African and global populations [19, 46,47,48]. The scientists speculate that this is related to changes in blood vessel physiology as people get older. The elasticity of the artery walls would be lost, resulting in a rise in blood pressure [49, 50]. According to previous studies , this could be linked to hormonal changes in both sexes at different ages. As a result, frequent monitoring is essential for detecting hypertension early in the menopausal transition.
Furthermore, the results of our study show that obesity is associated with a high prevalence of prehypertension and hypertension. Data from the literature in North Africa [19, 52] and around the world [46, 53] significantly corroborated this conclusion.
This link was frequently discovered among women [35, 46], and as a result, it has become a major public health issue, particularly in developing nations. As a result, WHO classified it as a “global pandemic” Weight gain as a result of improved living standards and decreased physical activity results in increased blood flow to various vital parts of the body like organs and tissues in response to their increased metabolic demands. As a result, the artery walls will be subjected to increased pressure . However, data from Tanzania and Uganda revealed that the population with a high BMI and central obesity had a low proportion of hypertension .
Furthermore, our results showed that there was a correlation between the prevalence of AO and the risk of developing prehypertension and hypertension. This matches respectively the findings of Mammeri et al.  and Midha et al. . It appears to be linked to the mechanisms of sympathetic nervous system hyperactivity and renin-angiotensin system activation, according to some authors. By causing peripheral vasoconstriction, these mechanisms can cause hypertension. Dyslipidemia and metabolic dysregulation caused by dietary changes are also risk factors [56, 57]. Consumption of saturated animal fats and processed carbohydrates has increased in recent years, but consumption of fruits and vegetables has dropped .
Hypertension in Algeria’s population was found to be positively correlated with marital status (separated/divorced), as in many previous studies. The authors [19, 58] have extensively reported on these findings. It is noted that separated or widowed people compared to married people are more susceptible to have diseases such as anxiety and depression, which explains the risk of developing HBP. Hypercholesterolemia was also a factor in the development of hypertension in our study. This result supports the findings of a number of researche [19, 40, 59]. The direct reasons for this affinity are attributed to urbanization and the nutritional transition associated to the risk of metabolic syndrome .
On the other hand, no association was found between the proportion of prehypertension and hypertension with respect to gender, and there was even a protective effect of female versus male gender in prehypertensive status. This result is in line with those mentioned by: Temmar et al.  and Ong et al. , who found no difference in hypertension prevalence between the sexes. This could be owing to both sexes having the same economic level. In contrast, Pereira et al.  discovered a higher average prevalence of BP in males than in women, particularly in developed countries. The gender differences could be explained by the molecular mechanisms underlying vascular, nervous system and kidney functions, that led to hypertension , while some studies from sub-Saharan Africa [61, 64, 65] found that the frequency of hypertension is clearly more prevalent for women than for men, with the hormonal profile and postmenopausal status of women accounting for this difference .
Furthermore, our study did not show a significant association between geographical region, locality and hypertension. Several studies [67, 68] have noted that people living in urban areas had a higher risk of hypertension. This could be interpreted as a change of lifestyle in these urban areas, including dietary habits, like access to fast food, high-fat, and energy-dense frozen food, and the availability of transport, all of which contributed to physical inactivity. Other studies [19, 34], established the link with the rural area. This is most likely due to the lack of screening as a result of the limited health infrastructure and the low level of education in these areas.
Similarly, we found no evidence of a link between hypertension and education, income, or occupation. These socio-demographic and economic determinants were frequently considered as contributing factors to the development of hypertension [69,70,71]. According to several studies, illiterate or less educated people, as well as a lack of resources, might had an impact on their general knowledge of how to prevent hypertension which led to unhealthy lifestyles.
In terms to diabetes, the present study found no association with hypertension, contrary to what was pointed out in several research that demonstrated a strong link between the levels of insulin secreted and BP [17, 53].
Although smoking, low fruit and vegetable consumption and physical inactivity play an important role in the development of cardiovascular events including prehypertension and hypertension [72, 73], our results contradicted this while some authors  reported the same outcome. The difference could be explained by a number of factors, on top of which is Algeria’s population low proportion of smokers and ex-smokers.
Second, the Mediterranean diet, which is described by several authors as balanced and helpful in improving blood glucose and cholesterol levels in metabolic syndrome, and in preventing diabetes .
Third, there has been an upsurge in physical activity among North Africans in recent years [19, 76].
Finally, this study provided important data on some cardiovascular risk factors linked to Algeria’s high rate of prehypertension and hypertension. On the one hand, it would be useful to spread within Algeria’s population awareness on the risks of CVD in order to detect HBP early and effectively treat people with prehypertension to prevent chronic hypertension. The introduction of healthy habits, therefore, should be encouraged .
This study has some limitations. First, the cross-sectional epidemiological study design used in the Algerian STEPwise survey, although used for its speed, efficiency and suitability for chronic diseases, it may not establish the causal relationship between risk factors for prehypertension and hypertension, or may it allow for the generalization of results to the whole population.
Second, the hypertension real prevalence may be inaccurate, either because of under- or over-reporting resulting from self-reporting of hypertension, or because of slight over- or underestimation due to the three measurements of systolic and diastolic BP which were taken only once on one day, or because participants could have recall bias, leading to redundancy in the information provided. Similarly, the study did not include people over 69 years old, which may also distort the overall prevalence of HBP in the population.
Third, the variables analysed in this study can only explain part of the disease determinants.
At the end, the link of genetic factors to the high prevalence of prehypertension and hypertension was not studied.