This study found a high prevalence of pharmacological treatment and blood pressure control among diagnosed hypertensive patients in two Cuban municipalities. Almost half of patients receiving treatment were taking two or more antihypertensive drugs. Hypertension control varied by health area within a municipality. Having post-primary education, not being obese and being of white ethnicity were positively associated with hypertension control.
Given that in Cuba the entire population is registered with a FDNP, who must carry out an individual risk assessment of the recorded population on a yearly basis, registers of patients provided by the Ministry of Health reflect the actual population’s health status. This is corroborated by the findings of the Third National Survey on Risk Factors in Cuba 2010–2011 where the prevalence of diagnosed hypertensive patients in the population above 15 years (2010) was 22.4% vs 20.4% found in the Ministry of Health registers . The study population consisted of a sample drawn from two of the 168 Cuban municipalities and thus it may not represent the national situation, in particular with respect to rural areas. Nevertheless, the found prevalence figures are consistent with national surveys  and an earlier similar study in the Cuban province of Cienfuegos . In order to minimize errors, international standardized recommendations for blood pressure measurement in population surveys were followed [16, 17]. However, blood pressure control was measured in a single visit, with the possibility of some false-positive uncontrolled hypertensive patients, resulting in an underestimation of hypertension control. Except for obesity, presence of comorbidities was self-reported without confirmation on clinical records or with diagnostic tests, which can be a limitation for their analysis as predictors. The use of self-report scales for measuring medication adherence also has potential limitations, especially regarding patients’ ability to understand the items and willingness to disclose information, which can affect questionnaire validity . Moreover, the 4-item Morisky MAQ  is only able to address barriers to medication-taking but not self-efficacy [21, 22]. Nevertheless, this test, validated in the USA with hypertensive patients, presented a reasonable specificity in identifying non-adherent behaviour . Another limitation is that factors such as smoking status, duration of hypertension or lipid profile, which besides being etiologically related to hypertension could also be associated with its control, were not included in the study.
The high prevalence of hypertension treatment and control among diagnosed patients found in this study is consistent with a previous study carried out in the Cuban province of Cienfuegos in 2001–2002 , suggesting more than a decade of sustainable outcomes. The recent PURE study  found an average prevalence of hypertension control among diagnosed patients receiving treatment of 41% in HIC and 27% in LMIC. Hence, the prevalence of hypertension control in Cuba found in the present study (58%) is considerably higher than the average in HIC and double that of LMIC. The figure is similar to what found in the Health Survey for England 2015, where 62% of treated patients had their blood pressure under control . A study comparing hypertension management in 20 countries among both aware and unaware systolic hypertensive patients, reports that the United States had the best age-standardized prevalence of systolic hypertension treatment and control in patients aged 35 to 84 years (81% for treatment and 59% for control) followed by Jordan (71 and 38%) and England (54 and 32%) . Due to the heterogeneity of methods among different studies, conclusions based on such comparisons should be interpreted with caution. Notwithstanding internationally outstanding figures, still more than a third of hypertensive patients did not have controlled hypertension, which warrants the attention of the Cuban health authorities.
Hypertension control at population level has been forwarded as a correlate measure of how well a health system functions, given that this condition is entirely dependent on the health system for its care and control . Constrains to provide integrated and quality chronic care have been associated with weak national health systems and fragmented health-care services [1, 27, 28]. For instance, in Sub-Saharan Africa, a region characterized by weak health systems, hypertension remains largely under-diagnosed and under-treated . From a health system perspective, at least three key drivers of successful hypertension control in Cuba can be identified. First and foremost, a PHC approach: Cuba, despite being a resource-constrained setting, ensures free and accessible quality care through FDNP  and is recognized for having a well-organized national health system that ensures inter-sectorial actions to promote health and wellbeing [12, 13, 29]. As underlined by the European Forum for Primary Care, a strong PHC system is better prepared to provide comprehensive health care and effectively co-ordinate the follow-up of chronic conditions . Besides Cuba, two other Latin-American countries, Brazil and Costa Rica, provide evidence of the effectiveness, efficiency and relevance of the PHC approach for the management of chronic conditions [28, 31,32,33]. Second, the high percentage of patients receiving pharmacological treatment found in this study confirms the reported availability, proper procurement and distribution of essential anti-hypertensive drugs in Cuba . Third, Cuba has one of the highest densities of physicians in the world: 67.2 per 10,000 population, only surpassed by rich countries such as Monaco and Qatar . Moreover, family doctors in charge of PHC services are specialists, with at least 3 years of postgraduate training . In summary, the main health system barriers to achieve blood-pressure control pinpointed by Ibrahim and Damasceno (namely scarce human resources, absence of a national policy for the control of NCDs, poor training of health personnel, overburdened and disorganized PHC and a deficient procurement and distribution of essential antihypertensive drugs) , have been overcome in the Cuban health system. Notwithstanding, the association of hypertension control with living in a specific health area suggests that hypertension control could be impacted at community level by improving health services functioning at micro-level.
Appropriate drug titration and combination therapies are also key elements for achieving hypertension control. According to international guidelines, more than two-thirds of hypertensive patients require treatment with more than one antihypertensive drug to achieve blood pressure control [3, 36, 37]. The proportion of patients taking two or more types of antihypertensive drugs found in this study (49%) was high compared to average international figs. , suggesting that clinical inertia is not an important barrier affecting adequate antihypertensive therapy in Cuba. Overall, the combinations of antihypertensive drugs found in this study are aligned with international guidelines [36, 37]. Moreover, the type and frequency of medications used are more similar to the pattern reported in HIC than in LMIC . Nevertheless, recent evidence showed that B-blockers are inferior to other drugs for the prevention of major CVD, stroke and renal failure  and they were not recommended by the Eight Joint National Committee for the initial treatment of hypertension . Therefore, Cuban health authorities should take appropriate measures to address the high use of B-blockers and decrease their prescription, especially as monotherapy or initial treatment.
Being on pharmacological treatment was not significantly associated with hypertension control, but the vast majority of patients were on pharmacological treatment and control in other hypertensive may have been achieved by lifestyle modifications, which were not explored in depth in the present study. International literature widely describes the positive effects that sustained lifestyle modifications such as weight loss, diets rich in fruits/vegetables, and sodium (Na+) reduction have on blood pressure (BP) control . Other non-pharmacological strategies recommended for patients with hypertension include tobacco cessation, decreased alcohol consumption and self-measured BP monitoring . However, this study, did not explore the effect of non-pharmacological approaches to blood pressure control. Pharmacological treatment and adherence to it was included in the final multivariate model, but the difference between the individual categories was not significant. This could possibly be explained by inherent limitations of the Morisky test for capturing actual adherence, which have been signaled before.
The lack of association of hypertension control with age, gender and socio-economic conditions could be explained by the equity in access to health care services in Cuba irrespective of gender or social condition, where all adults receive at least one home visit of their family doctor/nurse per year, a frequency that increases according to specific risk profiles or disabilities . The association between post-primary education and better hypertension control is consistent with other national and international reports [11, 41,42,43,44]. Furthermore, the high prevalence of post-primary education found in the study population (85%), is a significant factor related to achieving hypertension control in Cuba, as a higher education level is relevant for disease awareness and compliance to treatment [45, 46].
Obesity was found to be associated with poorer hypertension control. This is compatible with available evidence reporting a stable linear relation between adiposity and blood pressure, independent of age and body fat distribution . High BMI alone is a very well established risk factor for hypertension and obese individuals have increased relative risk for CVD . Obesity is a serious concern indeed for Cuba: in 2011, 45% of the Cuban population was overweight and 15% was obese .
In this study non-white hypertensive patients (mestizo or black) were more likely to have uncontrolled hypertension, regardless of socio-economic condition. Differences associated with ethnicity could be related to lifestyle differences or to genetic factors such salt sensitivity, which is more common in black people . There are no specific studies on hypertension and cardiovascular complications among black communities in the Latin American and Caribbean region . Studies done in United States showed that hypertension is more common, severe and leads to more clinical sequelae in African Americans compared to non-Hispanic whites . Nevertheless, since African Americans also have a greater prevalence of other cardiovascular risk factors, hypertension has been mainly attributed to environmental and lifestyle factors and socio-economic condition rather that to genetically defined racial differences [35, 36].
Lowering blood pressure significantly reduces the risk of major cardiovascular events and all-cause mortality  and hypertension control at population level should be of the highest priority in all countries. Evidence also indicates that only well-functioning health systems are able to address NCDs effectively and equitably . Based on the results reported here, a set of interventions - at health service and community level - aimed at increasing the effectiveness of hypertension management programs in both municipalities will be designed, implemented and evaluated.