Transcript Slide Presentation

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
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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 20-29 year olds to over 75% in those 80-89 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, 2010
http://www.cdc.gov/bloodpressure/index.htm
http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_stroke.htm
http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_bloodpressure.htm
http://www.commed.vcu.edu/Chronic_Disease/syllabus/HBP_stroke.html
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 120-139 mmHg and/or DBP 80-89 mmHg
• Stage 1 hypertension
• SBP 140-159 mmHg and/or DBP 90-99 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
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Genetics
Obesity
Physical inactivity
Alcohol intake
Dietary sodium and potassium
intake
Stroke
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Hypertension
Atrial fibrillation
Diabetes
Cigarette smoking
Physical inactivity
Poor diet
Hypercholesteremia
Obesity
Dyslipidemia
Chronic Disease Epidemiology and Control, 2010
http://www.strokeassociation.org/idc/groups/stroke-public/@wcm/@hcm/@sta/documents/downloadable/ucm_463745.pdf
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 reninangiotensin 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
Hypertension Prevalence
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
http://www.cdc.gov/bloodpressure/facts.htm
http://www.strokeassociation.org/idc/groups/stroke-public/@wcm/@hcm/@sta/documents/downloadable/ucm_462739.pdf
Prevalence of hypertension among adults aged 18 and
over, by sex and race: United States, 2011-2014
http://www.cdc.gov/nchs/data/databriefs/db220.htm
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, 2011-2014
http://www.cdc.gov/nchs/data/databriefs/db220.htm
Starting blood pressure values are significant
• Individuals with a SBP <140 mmHg and DBP 85-89 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 35-64 years old and 18.5%, 29.0%, and 52.5% aged 65-94 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
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_15_burden_stroke.pdf?ua=1
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
http://www.cdc.gov/bloodpressure/facts.htm
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2015/salt_editorial.pdf
• Stroke is a top-ten leading cause of death in the United States and
around the world
• 3rd leading cause of death for women in the U.S.
• 5th 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
http://www.strokeassociation.org/idc/groups/stroke-public/@wcm/@hcm/@sta/documents/downloadable/ucm_462739.pdf
http://www.who.int/mediacentre/factsheets/fs310/en/
http://www.cdc.gov/nchs/data/nvsr/nvsr57/nvsr57_14.pdf
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_16_death_from_stroke.pdf?ua=1
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
http://www.cdc.gov/bloodpressure/facts.htm
http://www.cdc.gov/dhdsp/data_statistics/fact_sheets/fs_stroke.htm
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
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Weight reduction
Salt intake reduction
Dietary potassium increase
Moderation of alcohol intake
Physical activity
Change in dietary pattern
Chronic Disease Epidemiology and Control, 2010
http://www.commed.vcu.edu/Chronic_Disease/syllabus/HBP_stroke.html
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, 2010
http://www.cdc.gov/bloodpressure/facts.htm
Three Treatment Stages for Stroke
• Prevention
• Therapy immediately after the stroke
• Post-stroke rehabilitation
http://www.ninds.nih.gov/disorders/stroke/stroke.htm
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
http://www.strokeassociation.org/STROKEORG/Professionals/Stroke-Prevention-Resources_UCM_451918_SubHomePage.jsp
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.
http://www.nejm.org/doi/full/10.1056/NEJMoa1415061
http://www.strokeassociation.org/idc/groups/stroke-public/@wcm/@hcm/@sta/documents/downloadable/ucm_462739.pdf
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_20_personal_choices.pdf?ua=1
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_20_personal_choices.pdf?ua=1
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 1999–2000
• 53.3% for 2009–2010
• Remained stable through 2013–2014
• Currently, more than one-half of adults with hypertension have
their hypertension under control (54.0%)
http://www.cdc.gov/nchs/data/databriefs/db220.htm
Age-adjusted trends in hypertension and
controlled hypertension among adults aged 18
and over: United States, 1999-2014
http://www.cdc.gov/nchs/data/databriefs/db220.htm
Prevalence of controlled hypertension among adults aged
18 and over, by sex and age: United States, 2011-2014
http://www.cdc.gov/nchs/data/databriefs/db220.htm
Prevalence of controlled hypertension among adults aged
18 and over, by sex and race: United States, 2011-2014
http://www.cdc.gov/nchs/data/databriefs/db220.htm
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 2008-2014 more than 165,000 women have been reached
http://www.cdc.gov/wisewoman/
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
http://www.cdc.gov/dhdsp/programs/stroke_registry.htm
Population-wide behavioral and
environmental influences
http://www.cdc.gov/bloodpressure/facts.htm
http://www.who.int/cardiovascular_diseases/cvd_atlas_21_prevention_population.pdf?ua=1
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:
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50% (40%) in 80-89 year olds
70% (60%) in 70-79 year olds
90% (80%) in 60-69 year olds
100% (90% and 110%) in 50-59 and 40-49 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
http://www.ninds.nih.gov/disorders/stroke/stroke.htm
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
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2015/2Txornot2Tx_BMJ_Sept.pdf
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2015/cholguide.pdf
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2015/salt_editorial.pdf
“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.”
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2012/controversiesBMJ.pdf
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_18_research.pdf?ua=1
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 “
http://www.commed.vcu.edu/Chronic_Disease/hypertension/2015/cholguide.pdf
Questions/Comments/Concerns?