Data on current trends in hypertension prevalence and changes over time in the levels of attainment at each step of its care cascade (i.e. awareness, treatment and control) are required in the LAC region. Our analysis of Chilean health examination survey data indicates that around three-in-ten adults aged 17 years and over had hypertension, with the prevalence from 2003 to 2017 showing a small but significant decline (from 37% to 31% for males; from 31% to 30% for females). Mean SBP and DBP levels also decreased at the population level over the 15-year period. Adopting the 2017 ACC/AHA hypertension guideline would increase prevalence by about 55% in relative terms, resulting in an additional 2.3 million adults being eligible for antihypertensive treatment. Using self-reported data rather than ATC codes to ascertain use of antihypertensive treatment had little impact on the prevalence estimates.
Average BP levels fell steadily worldwide between 1975 and 2015 . Some uncertainty exists about the drivers of the worldwide trends in average BP and hypertension prevalence, particularly as the reductions in BP levels have been accompanied by increases in a number of the leading risk factors for high BP, including high body mass index (BMI) and diabetes . Our results also showed decreases in average BP levels regardless of treatment status (with the exception of no significant change in mean SBP among females on treatment), while evidence from other studies analysing Chilean data over the same time period shows that levels of obesity have increased, whilst levels of physical inactivity were unchanged . The decrease in BP can be explained at least partially by the increased detection of high BP by health care professionals (awareness) and by the subsequent wider uptake of antihypertensive treatments . Evidence consistently shows that higher levels of hypertension are associated with lower levels of income and formal education [18, 19]. Therefore, some of the BP decline in Chile could be attributed to the decrease in absolute poverty from 29% to 9% and the increase in the average length of time spent in formal education from 10 to 11 years between 2009 and 2017 . The decline in hypertension prevalence in Chile was similar to that observed in other HICs, potentially driven by the decrease in risk factors which buffered the expected increase due to the rises in obesity and diabetes. For instance, salt intake  and exposure to dietary trans fatty acids and smoking decreased over time [17, 22]. Stop signs were introduced in 2012 on packaged foods “high in” energy, sodium, sugars, and saturated fats, which is contributing to a healthier food industry reformulation . Despite the progress over the 15-year period, the prevalence of hypertension (defined as BP≥140/90 mmHg or use of antihypertensive treatment) is currently slightly higher in Chile compared to that found in HICs .
According to our results, current levels of attainment at each step of the hypertension care cascade are higher in Chile compared to most LMICs , while compared to HICs , levels of awareness, treatment and control were lower, higher and similar respectively. We found that levels of treated and controlled hypertension significantly increased from 2003 to 2017, while levels of awareness increased only among males between 2003 and 2010. In agreement with global trends, our analyses showed that the proportions of adults reaching each stage of the care cascade were similar to those reported in other HICs and were higher than those in LMICs between 2000 and 2010 [1, 9]. Several explanations have been put forward for the global improvement in levels of hypertension awareness, treatment and control, including increases in BP screening at the primary care and community levels, securing better treatment availability, reducing treatment costs, improving treatment adherence and preventing clinical inertia . The GES was launched in Chile in 2005 with a wide marketing strategy and helped to disseminate evidence-based guidelines with simplified recommendations nationwide. In 2014, the law was enforced with an additional regulation called FOFAR, which, for the publicly insured, warranted medicines free-of-charge for hypertension, diabetes and dyslipidaemia. Although we cannot directly assess the impact of these programmes with the ENS data, we can speculate that they have had at least some positive impact through the improvements in treatment and control levels presented here.
Our analyses show no significant difference in hypertension prevalence by gender. However, levels of attainment at each cascade step were higher among females. These gender disparities were also reported among LMICs  and HICs [1, 10]. However, the gender gap was wider in Chile than in other HICs. For example, current levels of controlled hypertension were 41% and 26% higher in relative terms among females in Chile (according to our results) and in HICs, respectively . Potentially these gender disparities arise from higher levels of health care services utilisation among females and lower long-term adherence to antihypertensive treatment among males . Although gender disparities exist, the trends show some evidence of faster improvements among males. Our analyses show that the Chilean 2010-2020 health goal of increasing the level of controlled hypertension by 50% in relative terms has been achieved among males, but is only at the halfway point among females since the relative increases from 2010 to 2017 were 97% and 24% for males and females respectively .
Using the 2017 data we found that implementing the 2017 ACC/AHA guideline – i.e. lowering the BP threshold from 140/90 mmHg to 130/80 mmHg - would result in 2.3 million more Chilean adults being classed as hypertensive and so be eligible for antihypertensive treatment. This is in addition to the 1.5 million hypertensive adults currently untreated according to the current (JNC 7) guideline. The relative increase of about 55% in hypertension prevalence as a result of adopting the 2017 ACC/AHA guideline seems to be higher in Chile than those estimated (using similar methods) in the United States (27%), China (45%) and Spain (42%) [11, 12], but lower than in Peru (130%) . The definitions in the Peruvian study were based on high BP alone, however, and so is not strictly comparable with our findings. This new scenario would be a massive challenge for Chile, requiring significant increases in public health expenditure, especially for health-care services and medicines. Implementing the new guideline would potentially increase the absolute number of hypertensives who are aware and on treatment over time. There is a growing debate about the merits of lowering the BP threshold, including concerns about the expected costs of implementation .
One strength of our study is the use of nationally representative health examination survey data, in contrast to the Prospective Urban Rural Epidemiology (PURE) study which covers only a few cities , and our use of objective measures which overcome the limitations of self-report data. However, our study has a number of limitations. First, to ensure comparability across the three surveys, we used the average of the first and second BP readings. Compared to using the average of the second- and third-readings, our approach could have slightly (<1%) overestimated hypertension prevalence and underestimated levels of controlled hypertension . Second, according to the JNC 7 and 2017 ACC/AHA guidelines, the diagnosis of hypertension should be made at follow-up visits.[7, 8] Evaluation of BP during a single visit (as done in the ENS surveys) may overestimate the true prevalence as raised BP is not necessarily persistent. According to analyses of Chilean data, a small but statistically significant reduction in hypertension prevalence (1%) was found when BP measurement was repeated in a follow-up visit . Moreover, the impact of the ‘white coat effect’ (i.e. transient increase in BP produced by the presence of a healthcare professional) or of ‘masked hypertension’ (i.e. nonelevated BP in clinical but elevated in ambulatory monitoring) on levels of hypertension could not be estimated in our study.
Third, recall bias could also have impacted on our estimated levels of awareness and treatment. Ascertaining use of antihypertensive treatment based on ATC codes from the medicine inventory could have produced a slight overestimation of prevalence since some medicines can be used for other conditions without the co-existence of hypertension. However, our sensitivity analysis showed that the magnitude of bias was small: suggesting minor recall bias (versus self-reported use) or low use of antihypertensive treatments for conditions other than hypertension. Fourth, although the same BP monitor was used in each survey, use of different models may have weakened comparability to some extent. Finally, as in other nationally representative health examination surveys, levels of response to the Chilean health survey have decreased over time. However, the current levels of response are comparable to those achieved by other national health examination surveys .
In conclusion, mean levels of BP in the untreated and treated populations have declined in Chile during the last 15 years (with the exception of no significant change in mean SBP among females on treatment), while levels of treatment and control among adults with hypertension have increased. The introduction of Universal Access to care for hypertension in 2005 may have accounted at least partly for the rise in levels of treatment and control since 2003. Regardless of the hypertension definition, innovative and collaborative strategies are needed to improve levels of attainment at each step of the hypertension care cascade, including the promotion of screening and access to care, together with interventions to increase treatment coverage and its adherence, especially among males and high CVD risk populations.