The Epidemiology of Hypertension: Latest Data and Statistics

Hypertension may be a largely asymptomatic condition -- but the consequences are far from insignificant. New data report that hypertension is the largest cause of the absenteeism that, in addition to "presenteeism," costs US businesses as much as $30 billion per year -- with clear implications for what businesses should be doing to address this problem. Another report documents hypertension as the single greatest cause of long-term healthcare in Europe. A third report finds that hypertension, in all its forms, is on the increase again in young people and adolescents (after years of decline), concomitant with the "epidemic" of obesity, while another US study, after discussion of the guideline definition of adolescent hypertension, reports that hypertension is underdiagnosed in this population. Finally, a new study carefully dissects the relative contributions of daytime vs nighttime blood pressure readings for predicting future events.

New Report Documents Economic Impact of Hypertension in the United States

A report published in October by the American Hospital Association shows the number of work days lost or that are unproductive due to chronic health conditions such as hypertension, diabetes, and asthma have significant effects on the national and local economies.[1] On average, about 164 million work days are lost annually due to these 3 chronic conditions, at a cost of $30 billion to employers, researchers report.

In 2006, for every 1000 working Americans aged 18-64 years, an estimated 1221 work days were lost due to asthma, diabetes, or hypertension. Asthma accounted for most of the time lost, at 927 days per 1000 working Americans. Hypertension and diabetes accounted for, respectively, 181 days and 112 days lost per 1000 workers. Thus in 2006, for every 1000 US workers, 4.5 weeks of work were lost due to an episode of hypertension.

Workplace absenteeism due to these conditions varied widely by region and by state. Hypertension accounted for 200 days missed per 1000 employees in the Southeast but fewer than 160 days missed in the North and Southwest. At the extremes of lost-work hours due to hypertension were:

* California had the highest workplace absenteeism, at 2,761,000 lost work days per year, at an estimated cost to employers of $522 million annually;

* The next 4 highest-ranking states were Texas, Florida, New York, and Illinois, with over 1,000,000 working days lost due to hypertension, at a cost ranging from $191 to $335 million;

* The state with the lowest workplace absenteeism due to hypertension was Wyoming, with 42 lost work days per year, costing $4 million; and

* The next 4 states/areas least-affected by hypertension were the District of Columbia, Alaska, North Dakota, and Vermont, all with a loss of < 60,000 work days due to hypertension in 2006.

The report also highlights productivity lost due to "presenteeism" (ie, when people are at work, but are not fully functioning because of illness or other medical conditions). Presenteeism can cut individual productivity by one third or more and, according to the report, health-related costs due to presenteeism can be higher than those related to absenteeism. The average annual cost of presenteeism per employee with hypertension is estimated to be $247. However, the report acknowledges that presenteeism is difficult to measure.

The report says that employers increasingly recognize that they have an important role to play in promoting health and productivity. More than 100 of the 1000 largest employers in the United States currently offer on-site care, including clinics with occupational healthcare, primary care, and pharmacy services, and this number is forecast to increase to at least 250 of the top 1000 by the end of 2007. The report cites a number of examples of health promotion programs, which 90% of all US employers with ≥ 50 employees claim to have initiated and that can result in significant decreases in blood pressure and cholesterol among participating employees.

The report also points to the cost savings that can result from such programs, citing a survey that found an average savings of $5.93 for every $1 spent, as well as an average reduction in sick leave absenteeism of 28% and health costs of 26%.[2] Employers also believe that offering health insurance contributes to better employee health and helps reduce absenteeism. In addition, workers who are entitled to paid sick leave take fewer sick days and are less likely to come to work sick and thus are more likely to be productive at work.


Commenting on the report, Rich Umbdenstock, president and chief executive office of the American Hospital Association said, "Millions of Americans are unnecessarily suffering from chronic conditions. One thing this study demonstrates is the need to keep people feeling better -- able to go on with their lives and work. We can manage chronic conditions. The message is clear, preventive medicine and wellness programs must be central to our health care system."


Concurrent with the hypertension trends, obesity was seen to increase from the time of the earliest survey (1963 to 1970), with the blood pressure rise lagging about 10 years behind this trend. In this study, both body mass index (BMI) and waist circumference were significantly associated with hypertension, although the increase in waist circumference (abdominal obesity) explained more of the blood pressure/hypertension increase than the increase in BMI (general obesity). In this study, obesity as measured by BMI or waist circumference was estimated to account for about 44% of the increase in hypertension and for 27% (BMI) and 68% (waist circumference) of the increase in prehypertension.

Implications and Comment

These new findings have implications for the public health burden of cardiovascular disease, particularly the risk of new cardiovascular disease, the researchers believe. "This is a major public health problem," Dr. Din-Dzietham said. "Unless this upward trend in high blood pressure is reversed, we could be facing an explosion of new cardiovascular disease cases in young adults and adults. To reverse the upward trend at the beginning is good, and that's why we need to act now."

The results of a study published in The Lancet[9] appear to challenge the consensus that nighttime blood pressure measurements are of greates predictive value for cardiovascular complications. After analyzing individual data from over 7000 subjects, José Boggia, MD (Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay) and colleagues found that the predictive accuracy of daytime and nighttime blood pressures and the night-to-day blood pressure ratio depended on the outcome under study.

For fatal endpoints, the nighttime blood pressure was more predictive than the daytime blood pressure, and the night-to-day ratio predicted total, cardiovascular, and noncardiovascular mortality. In contrast, for fatal combined with nonfatal outcomes, the daytime blood pressure was as valuable as the nighttime blood pressure, and the night-to-day ratio has little prognostic accuracy.

The researchers used data from the International Database on Ambulatory blood pressure monitoring in relation to Cardiovascular Outcomes, a resource of longitudinal population studies that was set up to investigate the extent that ambulatory blood pressure improves risk stratification.[10] The data in this analysis came from 7458 participants (mean age 56.8 years) who underwent 24-hour blood-pressure monitoring in 6 prospective population studies carried out in Belgium, Denmark, Sweden, China, Japan, and Uruguay. Of the 3436 (46%) subjects who had hypertension, 1637 (48%) were taking antihypertensive medication.

In the overall study population, median follow-up was 9.6 years. During follow-up, 983 participants died (14 per 1000 person-years) and 943 had a fatal or nonfatal cardiovascular complication (13.6 per 1000 person-years). There were more noncardiovascular than cardiovascular deaths (560 and 387, respectively). Of the cause-specific first cardiovascular events, 51 were fatal strokes and 369 were nonfatal strokes. Cardiac events consisted of 146 fatal and 379 nonfatal events, including 65 fatal and 186 nonfatal cases of acute myocardial infarction, 30 deaths from ischemic heart disease, 30 sudden deaths, 21 fatal and 142 nonfatal cases of heart failure, and 51 cases of surgical or percutaneous coronary revascularization.

Dr. Boggia and his colleagues calculated multivariate-adjusted hazard ratios for daytime and nighttime blood pressure and the systolic night-to-day ratio, while adjusting for cohort and cardiovascular risk factors. They found that:

* Adjusted for daytime blood pressure, nighttime blood pressure predicted total (P < .0001), cardiovascular (P < .01), and noncardiovascular (P < .001) mortality;

* Conversely, adjusted for nighttime blood pressure, daytime blood pressure predicted only noncardiovascular mortality (P < .05), with lower blood pressure levels being associated with increased risk; and

* Both daytime and nighttime blood pressure consistently predicted all cardiovascular, cardiac, and coronary events (P < .05) and fatal and nonfatal stroke (P < .01).

In fully adjusted models, with correction for nighttime blood pressure, systolic daytime pressure lost prognostic significance for cardiac events, whereas diastolic daytime pressure become nonsignificant for cardiac and coronary events. After adjustment for daytime blood pressure, systolic and diastolic nighttime values were no longer significant for coronary events. With adjustment for the 24-hour blood pressure, systolic and diastolic night-to-day ratio predicted mortality, but not fatal plus nonfatal events. Antihypertensive drug treatment removed the significant association between cardiovascular events and the daytime blood pressure.


These results suggest that daytime blood pressure, adjusted for nighttime blood pressure, predicts fatal combined with nonfatal cardiovascular events, except in treated patients, in whom antihypertensive drugs might reduce blood pressure during the day, but not at night. One reason for this could be that antihypertensive treatment acts as a major confounder, the researchers suggest. Patients with more severe hypertension or a history of cardiovascular complications are more likely to be treated and at higher risk than other patients, and they take their medications during daytime, and that activity that lowers blood pressure wears off at night. This mechanism leads to a reduced daytime blood pressure, increased nighttime blood pressure, and a decreased night-to-day blood pressure ratio.

Participants with systolic night-to-day ratio value of ≥ 1 or more were older, at higher risk of death, and died at an older age than those whose night-to-day ratio was normal (≥ 0.80 to < 0.90). The researchers suggest that higher nighttime than daytime blood pressure might be a marker rather than a cause of a poor outcome.


Dr. Boggia and his colleagues say that the findings of this study support the conclusions that:

* Ambulatory blood pressure should be recorded during the whole day;

* Clinical decisions should be based on diagnostic thresholds for the 24-hour blood pressure rather than the dipping pattern; and

* Antihypertensive drugs should be administered so that the blood pressure is lowered over 24 hours, so that a normal night-to-day blood pressure ratio is preserved.

However, the researchers point out that there is no evidence supporting the efficacy of chronotherapy in terms of blood-pressure control or outcome. Furthermore, the classification of patients according to the night-to-day blood pressure ratio greatly depends on arbitrary criteria, is poorly reproducible, and has a different prognostic meaning according to the disease outcome under study, the prevailing 24-hour blood pressure level, and treatment status. They recommend that "in future publications any categorical representation of the night-to-day ratio be supported by continuous analyses adjusted for the 24-hour blood pressure and be stratified for treatment status."


The contrasting findings in untreated participants and treated patients suggest a need for an additional meta-analysis of individual data for ambulatory blood pressure that includes a substantial number of patients on treatment for hypertension, Prof. Laurent suggests. "Although the findings of Boggia and colleagues are in favor of recording the ambulatory pressure for the whole day, the question arises as to whether 24-hour blood pressure values from patients taking antihypertensive therapy should be interpreted differently from those of untreated participants," he proposes. He believes that the results of the study may have important clinical implications and significantly affect the next guidelines for ambulatory blood pressure measurement.


1. American Hospital Association. Healthy people are the foundation for a productive America. TrendWatch. Spring 2007.
2. Chapman LS. Meta-evaluation of worksite health promotion economic return studies: 2005 update. Art of Health Promotion Newsletter January/February 2003;6(6):1-16.
3. TNS Opinion & Social. Health in the European Union. Special Eurobarometer 272e/Wave 66.2. September 2007.
4. European Opinion Research Group. Health, Alcohol and Food Safety, Special Eurobarometer 186/Wave 59.0. December 2003.
5. Din-Dzietham R, Liu Y, Bielo M-V, Shamsa F. High blood pressure trends in children and adolescents in national surveys, 1963 to 2002. Circulation. 2007;116:1392-1400.
6. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Pediatrics. 2004;114:555-576. Abstract
7. Falkner B. What exactly do the trends mean. Circulation. 2007;116:1437-1439. Abstract
8. Hansen ML, Gunn PW, Kaelber DC. Underdiagnosis of hypertension in children and adolescents. JAMA. 2007;298:874-879. Abstract
9. Boggia J, Li Y, Thijs L, et al; the International Database on Ambulatory blood pressure monitoring in relation to Cardiovascular Outcomes (IDACO) investigators. Prognostic accuracy of day versus night ambulatory blood pressure: a cohort study. Lancet. 2007;370:1219-1229. Abstract
10. Thijs L, Hansen TW, Kikuya M, et al; IDACO Investigators. The International Database of Ambulatory Blood Pressure in relation to Cardiovascular Outcome (IDACO): protocol and research perspectives. Blood Press Monit. 2007;12:255-262. Abstract
11. Laurent S. Day or night blood pressures to predict cardiovascular events. Lancet. 2007;370:1192-1193. Abstract

Linda Brookes, MSc

Medscape Cardiology. 2007; ©2007 Medscape
Posted 11/16/2007