The Epidemiology of Hypertension and Stroke EPID 624- Epidemiology of Chronic Diseases Sarah Kleinknecht

Presentation Overview Background Prevalence and incidence Defining Hypertension and Stroke Attributes Causes High-risk populations Morbidity and mortality Costs Interventions Individual and population-level Current programs Research and future challenges for public health

Background Hypertension and Stroke, in the U.S. and around the world

Prevalence and Incidence About a quarter of the adult world population in 2000 had hypertension More than 1 billion adults Projected to increase to 1.5 billion by 2025 Approximately 1 in 3 U.S. adults have hypertension Nearly 70 million people Ranges from 5% in year olds to over 75% in those years old Every year about 800,000 people in the U.S. have a stroke Someone has one every 40 seconds South and southeastern U.S. highest prevalence of both “Stroke belt” includes Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee Chronic Disease Epidemiology and Control,

What is Hypertension? High blood pressure Arterial blood pressure is the force that the circulating blood exerts on the walls of large, low-resistance arteries of the vascular system “The silent killer” No signs or symptoms Precise levels defining hypertension are those above which blood pressure-lowering interventions have been shown to reduce the risk of stroke and coronary heart disease Chronic Disease Epidemiology and Control, 2010

Diagnostic Values Normal Systolic (SBP) <120 mmHg Diastolic (DBP) <80 mmHg Prehypertension SBP mmHg and/or DBP mmHg Stage 1 hypertension SBP mmHg and/or DBP mmHg Stage 2 hypertension SBP >160 mmHg and/or DBP >100 mmHg Chronic Disease Epidemiology and Control, 2010

Pathophysiology Mean arterial pressure is the product of cardiac output and systemic vascular resistance Mechanisms are not entirely understood, but are dependent on the kidney, the sympathetic nervous system, and the renin-angiotensin system Compromise the balance of intake and output of fluids and electrolytes and the circulatory system fails SNS activation can cause short-term increases in BP by increasing HR, contractility, CO, vasoconstriction, and SVR Chronic Disease Epidemiology and Control, 2010

What is a Stroke? Classified as a cerebrovascular disease (also cerebrovascular accident or CVA) Occurs when an artery in the brain is either ruptured or clogged by a blood clot resulting in an interruption or a severe restriction of blood supply used to provide oxygen and nutrients to brain tissue Two main types: ischemic and hemorrhagic Ischemic strokes account for approximately 87% Chronic Disease Epidemiology and Control, 2010

Disease attributes Causes, high-risk populations, and consequences

Causes Hypertension Genetics Obesity Physical inactivity Alcohol intake Dietary sodium and potassium intake Stroke Hypertension Atrial fibrillation Diabetes Cigarette smoking Physical inactivity Poor diet Hypercholesteremia Obesity Dyslipidemia Chronic Disease Epidemiology and Control, 2010

Hypertension is the strongest independent risk factor for Stroke About 77% of people who have a first stroke have a blood pressure higher than 140/90 mmHg Different cohort studies have consistently shown that the incidence of stroke was on average 2.2 times higher in hypertensive as compared with normotensive subjects Relative effect of hypertension on stroke does not seem to depend on race or sex Chronic Disease Epidemiology and Control, 2010

Genetic Factors 40% of the variability in blood pressure is explained by genetic factors Identifying exact causes has been difficult Known to involve multiple nonallelic genes with small additive effects Risk of developing hypertension in persons younger than 50 doubles for each first-degree relative with a history of high blood pressure Chronic Disease Epidemiology and Control, 2010

Obesity The effect of excessive accumulation of body fat is mediated by over activation of the sympathetic nervous system and the renin- angiotensin system and alterations in endothelial and renal function Prevalence of hypertension at different BMIs: Normal 18% Overweight 30.8% Obese 42% About 50% of all new cases of hypertension are attributable to overweight and obesity combined Chronic Disease Epidemiology and Control, 2010

High-Risk Populations African American ancestry Family history of high blood pressure Men Older women Higher starting blood pressure values Previous stroke Chronic Disease Epidemiology and Control, 2010

Hypertension is common in almost all populations Like with average blood pressure, the prevalence depends strongly on age, sex, and race/ethnicity Consistent pattern: Higher in young men than in young women Higher in older women than in older men This change occurs at 30 years in African Americans and 50 years in other race/ethnicity groups Chronic Disease Epidemiology and Control, 2010

Race and Ethnicity Stroke Prevalence African‐Americans have nearly twice the risk for a first‐ever stroke than white people, and a much higher death rate from stroke, largely due to high blood pressure African‐Americans are also more likely to suffer a stroke at a younger age Among people ages 20 to 44, African Americans are almost 2 to 3 times more likely to have a stroke compared to Caucasians Hypertension Prevalence

Prevalence of hypertension among adults aged 18 and over, by sex and race: United States,

Average blood pressure increases with age SBP increases: Women From 110 mmHg at 20 years old to 160 mmHg at 80 years old Men From 120 mmHg at 20 years old to 150 mmHg at 80 years old DBP increases with age until about 50 years old and then remains constant or decreases Mostly explained by the loss of elasticity of the aorta and other large arteries that occurs normally with aging Chronic Disease Epidemiology and Control, 2010

Prevalence of hypertension among adults aged 18 and over, by sex and age: United States,

Starting blood pressure values are significant Individuals with a SBP <140 mmHg and DBP mmHg are 2-3 times more likely to develop hypertension than those with a similar SBP but a DBP <85 mmHg Among Framingham participants with optimum, normal, or high normal BP the 4-year risk of HTN was 5.1%, 18.1%, and 39.4% for ages years old and 18.5%, 29.0%, and 52.5% aged years old Chronic Disease Epidemiology and Control, 2010

Consequences of Hypertension Cardiovascular disease Coronary artery disease and congestive heart failure Neurological disease Stroke Chronic kidney disease Renal failure Premature death and disability Chronic Disease Epidemiology and Control, 2010

Burden of Disease According to the World Health Organization, “Hypertension is the second largest contributor to the burden of disease in both developed countries and developing countries with low mortality, and the fifth largest contributor in developing countries with high mortality” Chronic Disease Epidemiology and Control, 2010

Morbidity and Mortality Large impact due to high prevalence and strong association with cardiovascular and renal disease 9 million of all annual deaths in the world are caused by hypertension DALYs attributed to hypertension is 64 million, 4.4% of total Larger than that lost to smoking (59 million) and alcohol (58 million) More than 360,000 U.S. deaths in 2013 included hypertension as a primary or contributing cause Almost 1,000 deaths per day

Stroke is a top-ten leading cause of death in the United States and around the world 3 rd leading cause of death for women in the U.S. 5 th leading cause of death for men in the U.S. Accounted for 137,119 deaths in the U.S. in 2006 Represents over one-fifth of all CVD deaths It is the No. 1 preventable cause of disability

Costs Overall, hypertension and stroke cost the United States $46 billion and $34 billion each year, respectively This includes cost of health care services, medications, and missed days of work/productivity loss

Interventions Individual versus population-based costs and benefits

Prevention at the INDIVIDUAL Level

Screening and Early Detection Blood pressure measured at every routine clinic visit Re-measured in 2 years in those with normal levels and in 1 year in those with prehypertension Identify high-risk patients and monitor them Hypertension is easily diagnosed, but only 76% of hypertensive patients are aware of their condition Chronic Disease Epidemiology and Control, 2010

Primary Lifestyle modifications Weight reduction Salt intake reduction Dietary potassium increase Moderation of alcohol intake Physical activity Change in dietary pattern Chronic Disease Epidemiology and Control, 2010

Secondary Pharmacological treatment Aimed to avoid complications Generally indicated for those with stage 1 hypertension, although some prehypertensive individuals may benefit Thiazide diuretics are preferred initial drug Also commonly used: calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin type 1 receptor blockers, and Beta-blockers 7 in 10 adults with hypertension use medications to treat the condition Chronic Disease Epidemiology and Control,

Three Treatment Stages for Stroke Prevention Therapy immediately after the stroke Post-stroke rehabilitation

80% of Strokes are preventable Based on treating underlying risk factors Some risk factors (age, race, sex, family history) cannot be changed, but the majority can be changed, treated, or controlled More than half of Americans don’t know if they are at risk for a stroke Approximately 1 in 5 people do not know most of the warning signs

During/After a Stroke Acute therapies Try to stop it while it is happening by dissolving the blood clot or stopping the hemorrhage tPA versus thrombectomy versus endarterectomy versus stenting Importance of seeking treatment immediately In a study of patients who had experienced a stroke, someone other than the patient made the decision to seek treatment in 66% of the cases Post-stroke Goal is improvement in functional outcome Medication or drug therapy (antiplatelet agents or anticoagulants) to prevent another stroke About 25 percent of people who recover from their first stroke will have another stroke within 5 years.

Prevention at the POPULATION Level

Primary Complements detection and treatment at the individual level Aim is to lower average blood pressure in the whole population A reduction of 2 mmHg in the average DBP in the U.S. population would result in a 17% decrease in the prevalence of hypertension, a 6% lower risk of cardiovascular disease, and a 15% lower risk of stroke Focus efforts towards lowering blood pressure in individuals within the normal range as well as hypertensive and prehypertensive people Lifestyle modifications Community-based programs effective in raising awareness, increasing knowledge, and promoting lifestyle changes to improve blood pressure control Chronic Disease Epidemiology and Control, 2010

Controlled Hypertension No significant change in the U.S. prevalence of hypertension since 1999 (29.0% ) However, the prevalence of controlled hypertension among adults with hypertension in the United States has increased: 31.5% for 1999– % for 2009–2010 Remained stable through 2013–2014 Currently, more than one-half of adults with hypertension have their hypertension under control (54.0%)

Age-adjusted trends in hypertension and controlled hypertension among adults aged 18 and over: United States,

Prevalence of controlled hypertension among adults aged 18 and over, by sex and age: United States,

Prevalence of controlled hypertension among adults aged 18 and over, by sex and race: United States,

The WISEWOMAN program CDC’s Division for Heart Disease and Stroke Prevention 21 programs nationwide Provides low-income, under-insured or uninsured women with chronic disease risk factor screening, lifestyle programs, and referral services in an effort to prevent cardiovascular disease Priority age group is women aged 40–64 years From more than 165,000 women have been reached

PCNASR/PCNASP The CDC was directed by the U.S. Congress in 2001 to implement state-based registries to measure and track acute stroke care to improve the quality of that care As of July 2015, 9 states are being funded through the program Used to develop, implement, and enhance systems for collecting data on patients experiencing an acute stroke, to help analyze these data, and to use those results to guide quality improvement interventions for acute stroke care From 2005 through mid-2015 more than 550,000 patients benefitted from hospital participation in the PCNASP

Population-wide behavioral and environmental influences

Research and Future Programs Past studies, current questions, and potential topics to address

Effect of hypertension on cardiovascular mortality (Lewington et al.) Meta-analysis of cohort studies including more than 1 million adults Increase of 20 mmHg in SBP (or 10 mmHg in DBP) increased coronary heart disease death rate by: 50% (40%) in year olds 70% (60%) in year olds 90% (80%) in year olds 100% (90% and 110%) in and year olds Increased risk of stroke mortality by 50%, 100%, 130%, 160%, 180%, respectively Chronic Disease Epidemiology and Control, 2010

Current Stroke Research NINDS researchers are studying the mechanisms of stroke risk factors and the process of brain damage that results from stroke Basic research has also focused on the genetics of stroke and stroke risk factors Working to develop new and better ways to help the brain repair itself to restore important functions New advances in imaging and rehabilitation have shown that the brain can compensate for function lost as a result of stroke

Challenges Difficulty in diagnosis Office-based readings can be misleading, home blood pressure is superior in determining hypertension Most effective medical treatment is within less than 8 hours of symptom onset in stroke Uncertainty of evidence in many aspects For treatment of mild hypertension in individuals with no risk factors For the risks and benefits of certain diets (i.e. low sodium) Use of thrombolytics in stroke treatment

“The proper management of hypertension is arguably one of modern medicine’s most effective preventive interventions. It’s also one for which we have lots of clinical trial data, as well as a good number of well done meta-analyses. Yet controversy about how best to diagnose and treat hypertension in adults is still alive and well.”

Future work Strengthen the evidence Strengthen the implementation Strengthen the patient’s voice “Guidelines should inform but not dictate, guide but not enforce, and support but not restrict “

Questions/Comments/Concer ns?