Switching from JNC8 to 2017 ACC/AHA highlighted sharp increases in prevalence and drastic decreases in awareness, treatment, and control of HTN. Based on the 2017 ACC/AHA, half of the adults fall into the hypertensive category. Two-thirds of adults in the hypertensive category were unaware, indicating that they were undiagnosed. Among those with awareness, about one-third remains untreated, and among treated, less than 20% were controlled.
The increase in the prevalence by the use of 2017 ACC/AHA guideline in Iran is consistent with the adoption of 2017 ACC/AHA in other countries e.g. Nepal , China , and the United States [21, 22]. Adopting the new guideline, the largest increase in the prevalence was observed among young and middle-aged individuals, which is also reported in China .
The prevalence and awareness of hypertension in Iran (compared based on cutoff 140/90 mm Hg) resemble these outcomes in the middle-income countries [23, 24]. Despite a higher treatment rate in Iran, the rate of control stands at 39.1%, which is yet noticeably lower than Turkey with 53.9% in 2012 and Lebanon with 54% in 2014 .
Increases in age significantly increased prevalence, awareness, and treatment but decreased the control rate. The likelihood of prevalence increased by being overweight and obese, higher triglyceride, dyslipidemia, diabetes, and previous CVD history. Studies also reported higher prevalence among overweight, obese [26, 27], diabetics, and those with a history of CVDs . Higher awareness and treatment were also observed among those with comorbidity of diabetes and CVD . This indicates a higher chance of diagnosis and treatment for individuals living with such comorbidities.
By the use of 2017 ACC/AHA, a larger proportion of comorbid patients will fall into hypertension category (24%, 15%, 17%, and 11% more individuals with dyslipidemia, high triglyceride, diabetes, and CVD events respectively). Under 2017 ACC/AHA more high-risk adults might be covered by pharmacologic therapies and be protected against the progression of CVD and diabetic renal diseases [5, 29].
The proportion of participants with BP > 20/80 mm Hg based on 2017 ACC/AHA that were eligible for nonpharmacologic therapies were high; 97.9% needs to lower salt intake to <5 gram/day as recommended by WHO , 89.6% needs to consume sufficient fruits and vegetables, and 69.4% needs to lose extra weight. Though the Tanaka formula provided statistically better estimates for sodium intake in Iran , all three common formulas to estimate sodium intake (Kawasaki, Tanaka, and INTERSALT) were systematically biased with overestimation at lower levels and underestimation at higher levels of sodium intake . In light of this evidence, we note that the level of salt intake in Iran is much higher than the 5 g/d benchmark recommended by WHO, therefore at a higher level of sodium intake, underestimated sodium intake would still proceed with the recommended salt intake level. Thus, still, the percentage of those eligible to reduce salt intake remains too large.
Lifestyle factors LDL cholesterol, physical activity, and BMI had large effect sizes for lowering BP. Based on this finding, non-pharmacologic therapies for hypertensive patients might consider modifying these lifestyle factors. For low-risk adults (ASCVD <10%), falling into the hypertensive category under the new guideline, these lifestyle modifications could be recommended therapy.
We contribute to a better understanding of the burden of hypertension based on two distinctive guidelines. Taking more aggressive cut-off values 130/90 mm Hg resulted in a greater prevalence and lower effective coverage of hypertension. The largest increase in the prevalence was observed in indults aged 25-34. Due to a large population of this age group (16.8 million) in Iran, those falling into the hypertensive category by 2017 ACC/AHA remarkably increase from 1.2 million to 5.2 million. Despite the lowest awareness and treatment rate in this group, the control rate of them was highest among all age groups. This implies that targeting younger groups brings about larger benefits for health coverage programs and furthermore for society through avoided lost productivity . Given this potential benefit for Iran, the use of 2017 ACC/AHA might appeal to the upper-middle-income countries with a similar population profile .
Though adopting 2017 ACC/AHA led to the higher prevalence, yet not all adults falling into the hypertensive category would undergo antihypertensive medications . Based on 2017 ACC/AHA, 37.2% or 17.2 million Iranian adults >25 years were eligible for pharmacologic therapy and based on JNC8 28.6% or 13.4 million adults . With a minimum unit cost of treatment around $38 per person , pharmacologic therapies would annually cost $653 million and $510 million respectively under the 2017 ACC/AHA and JNC8 for all Iranian adults >25 years. Thus, treatment costs that the health system incur for pharmacotherapy under the 2017 ACC/AHA is only marginally higher than treatment cost based on JNC 8.
We found that hypertension is extremely uncontrolled in Iran. Control is by nature a co-creational outcome. Both patient behaviors and effective structure and process of care play a role in improving this outcome. Based on our findings, patient adherence to a healthy lifestyle and complementary insurance may improve the control rate [26, 27, 35]. We, however, call future research to examine other dimensions of effective structures and processes e.g. evidence-based care plan [36-38] and continuity of care [39, 40] to improve hypertension control.
This research is faced with several limitations including the challenge of causal inferences from cross-sectional survey data and potential misclassification in covariates. We claim no causal relationships, understanding that inferring a causal relationship from cross-sectional surveys is unequivocally a challenge. However, some criteria helping argue causal relationships are maintained; we relied on a compelling theoretical causal model with regard to examining preceding factors for the prevalence, awareness, treatment, and control of hypertension. It was followed by found associations between the focal variables as well as holding that the examined covariates, the causes, logically precede four outcomes .
We are also aware that there exists potential misclassification in covariates including particularly smoking and salt intake. We classified participants based on 10 g/d cutoff point for salt intake rather than the 5 g/d recommended cutoff point. We did so as a rather small number of participants had salt intake less than 5 g/d.
Our classification also disregards previous cigarette smoking history, which may affect the magnitude of effects on the outcomes. For instance, while being categorized as currently non-smoker, the participant may have previous smoking history and suffer from its consequence. The magnitude or direction of this classification of smoking remains to investigate . Furthermore, the effect of smoking status might be incompletely represented by our data choices. Since we only focused on daily cigarette smoking status, current smokers of other tobacco products were excluded from smokers.
The external validity of our findings is reasonably confidently maintained by the multistage random sampling methods with proportional to size samples. Participants were from all provinces (except one province) and from urban and rural areas. Given this, the validity of inferences about the identified relationships might be, though not assuredly, maintained over variations in persons or times .