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HYPERTENSION – WHY IS IT IMPORTANT FOR PUBLIC HEALTH

HYPERTENSION – WHY IS IT IMPORTANT FOR PUBLIC HEALTH. Heart Disease and Stroke Prevention . Dr. Yoga Nathan Public Health UL. What is Hypertension?. 160/95 mm Hg? 140/90 mm Hg?. How can we define `Hypertension’ or ` High blood pressure ’? BY DEFINING THE BP LEVEL ABOVE WHICH IT

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HYPERTENSION – WHY IS IT IMPORTANT FOR PUBLIC HEALTH

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  1. HYPERTENSION – WHY IS IT IMPORTANT FOR PUBLIC HEALTH

  2. Heart Disease and Stroke Prevention Dr. Yoga Nathan Public Health UL

  3. What is Hypertension? • 160/95 mm Hg? • 140/90 mm Hg?

  4. How can we define `Hypertension’ or`High blood pressure’? BY DEFINING THE BP LEVEL ABOVE WHICH IT IS BENEFICIAL TO REDUCE BP • This the definition generally used • Arbitrary definition, changing over time • 1950s DBP 120 • 1960s DBP 110 • 1980s DBP 100 SBP 160 • Now DBP 90 SBP 140

  5. CAUSES OF HIGH BLOOD PRESSURE A small proportion of individuals with high blood pressure have a specific medical cause (secondary hypertension): <1% in general population <5% in medical clinics The rest have no specific medical cause (primary or essential hypertension)

  6. CAUSES OF SECONDARY HYPERTENSION • -Coarctation of aorta • -Renal and renal vascular disease • -Adrenal disease • cortical 1 hyperaldosteronism, • Cushing’s syndrome • medulla phaeochromocytoma • -Pregnancy • -Drugs esp OCP, HRT

  7. Characteristics of populations in whichblood pressure does not rise with age • Rural communities in less developed settings • Hunter gatherer, subsistence diet • low in fat, salt, alcohol • Low mean body mass index • High physical activity • Low stress levels (?)

  8. Studies of migration and BP -Generally show that blood pressure patterns change (increase) to those of the host population: • Change generally occurs within 6 months • Strong evidence for ENVIRONMENTAL influence on population BP • May be exceptions – high BP in African- Caribbeans may have genetic basis

  9. Causes of `essential’ hypertensionFactors contributing to higher BP (high vs low comparison) • SBP higher by:- • -High body mass index 15 mmHg • -High alcohol intake 8 mmHg • -High salt intake 5 mmHg • -Low potassium intake 5 mmHg • -Low fibre/high fat 2-3 mmHg • -Physical inactivity 2-3 mmHg • -Stress ????

  10. Risk factors for high blood pressure • Age being older • Ethnicity African-Caribbean • Family history positive • Body mass Overweight/obese • Alcohol intake high

  11. Which is more strongly related to risk, systolic or diastolic? • -Both are important, systolic slightly more so • -In older people, `high’ systolic BP can occur with `normal’ diastolic pressure (isolated systolic hypertension), is associated with increased CV risk

  12. How strong are the relative risks ofhigh blood pressure (60-69 years)? • -Usual systolic BP 20 mmHg higher:- • relative risk of stroke 2.32 • relative risk of CHD 1.85 • -Usual diastolic BP 10 mmHg higher:- • relative risk of stroke 2.50 • relative risk of CHD 1.79 Applies above SBP 115, DBP 75 mmHg Prospective Studies Collaboration, Lancet 2002

  13. Distribution of Blood Pressures in Adults in the United States 90th percentile 95th percentile Source: NHANES II

  14. Stroke Rates by Blood Pressure Level Source: Framingham Heart Study, 1980

  15. Mortality Due to CHD per Quartile of Systolic BP 140 United States Northern Europe Mediterranean southern Europe Inland southern Europe Serbia Japan 130 120 110 100 90 80 Mortality From CHD (No./10,000 Person Years) 70 60 50 40 30 20 10 0 110 120 130 140 150 160 170 Systolic Blood Pressure (mm Hg) (Adjusted for age, serum TC, current smoking status for each quartile) Van den Hoogen PCW, et al, for the Seven Countries Study Research Group. N Engl J Med. 2000;342:1-7.

  16. “Natural History” of 35 yr old White malewith Untreated Hypertension

  17. Hypertension Affects Target Organs Hypertension • Angina pectoris • Unstable angina • Myocardial infarction • Sudden death • Heart failure • TIA • Ischemic stroke • Hemorrhagic stroke • Renovascular disease • Renal failure • Claudication • Aneurysm • Critical limb ischemia

  18. High BP increases the risk of:- • -Coronary (ischaemic) heart disease • -Stroke (all types) • -Ischaemic stroke • -Haemorrhagic stroke • -Subarachnoid haemorrhage • -Heart failure • -Hypertensive heart disease • -Sudden death • -Renal failure • -(All-cause mortality) How do we know this?

  19. Population-Based Strategy Reduction in SBP mmHg 2 3 5 SBP Distributions After Intervention Before Intervention Reduction in BP % Reduction in Mortality Stroke CHD Total -6 -4 -3 -8 -5 -4 -14 -9 -7 Hypertension 1991;17:I-16–I-20.

  20. SOURCES OF DIETARY SALT Other Sodium Table Salt Water Cooking Salt Processed Food Source: James et al. The dominance of salt in manufactured food in the sodium intake of affluent societies. Lancet 1987;8530:426-428.

  21. Sodium Intake and BP • Raised blood pressure is the biggest single cause of cardiovascular disease accounting for 62% of strokes and 49% of heart disease. • Strokes and coronary heart disease kill more people around the world than any other cause of death – around 12.7 million people each year. • It is estimated that reducing salt intake by 6g a day could lead to a 24% reduction in deaths from strokes and an 18% reduction in deaths from coronary heart disease, thus preventing approximately 2.6 million stroke and heart attack deaths each year worldwide.

  22. Hypertension • Preventable • Treatable • Controllable • Why is so Difficult to Do?

  23. Lowering blood pressure and relative risk of cardiovascular disease Sustained reduction in blood pressure over about 5 years effectively reverses the risks of the higher pressure • -If usual diastolic BP 10 mmHg lower:- • relative risk of stroke reduced by about 60% • relative risk of CHD reduced by about 44%

  24. Implications Greater BP reduction gives greater CV risk reduction • -Similar BP reduction (e.g. 10 mmHg) will reduce • relative risk of CVD by similar amount, whatever thestarting blood pressure • Because the relations of BP and CVD risk arecontinuous there is no rational target for BPreduction(pragmatic targets for patients on treatment) Br HypSoc SBP <140 DBP < 85 mmHg

  25. Who should have their BP lowered? -The traditional view: The reason for lowering blood pressure is that it is high…. `People who need their blood pressure lowered are those who have a high blood pressure’ -The new view The reason to lower blood pressure is to reduce the risk of cardiovascular disease `People who need their blood pressure lowered are those who are at high risk of cardiovascular disease (almost irrespective of their blood pressure)’ -The third (middle) way `Blood pressure should be treated on its merits but should take account of overall CV risk’

  26. Lifestyle Modifications

  27. Models of Helping and Coping* Responsibility for a Problem(Who is to blame?) Other Self • Compensatory Model • Person feels deprived • Person needs power (skill) • Moral Model • Person feels lazy • Person needs motivation Self Responsibility for a Solution(Who will control the future?) • Enlightenment Model • Person feels guilty • Person needs discipline • Medical Model • Person feels ill • Person needs treatment Other * Brickman, American Psychologist37(4):368–384, April 1982.

  28. “Cured” Model • Patient believes • His diagnosis • Hypertension is serious • In the efficacy of medicine • He can control HBP with doctor’s help. Patient cooperates with doctor, and BP is controlled. Patient told, “It’s okay now.” Patient doesn’t want to think of himself as “sick.” Patient believes doctor meant “Stop taking the medicine” when he said, “You’re under control.” Patient doesn’t understand the difference between control and cure. He thinks he’s “cured”. Patient receives no re-education about the lifelong need for treatment. Patient stops medicine and visits. Belief that he’s “cured” and “told to stop medicine” is reinforced. Patient receives no call from doctor. Drops out

  29. Nervous Tension Model • Patient believes • His diagnosis • In medicine and its efficacy to lower blood pressure • In the need for lifelong treatment • In the hazard of HBP if left uncontrolled Patient believes hypertension is “nervous tension.” Patient believes he can control HBP with “self-discipline” or by “accepting life.” Patient takes medicine when he feels tense and believes this adequately lowers BP. Patient believes he can tell when BP is high since he knows when he is tense. Patient believes medicine is needed only to lower blood pressure, not to keep it low. Patient feels no need to see doctor and keep appointments because he knows when to take medicine. Drops out Medical system does not follow up to recall patient for appointments. Patient believes he’s adequately controlled—reinforced by lack of professional intervention. Patient has no symptoms to tell him that blood pressure is uncontrolled. Remains Uncontrolled

  30. Public Health Approaches to CVD • Public health approaches, (e.g. reducing calories, saturated fat, and salt in processed foods) can achieve a downward shift in a population’s BP. • Reducing overall BP by only a few mm Hg could affect overall CVD morbidity and mortality by as much or more than treatment alone. • Public Health approaches provide an attractive opportunity to interrupt and prevent the costly cycle of managing hypertension and its complications.

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