Dr. Yoga Nathan
Public Health
UL

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
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

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)
a)
b)
c)
d)
e)
f)
g)
h)
-Coarctation of aorta
-Renal and renal vascular disease
-Adrenal disease
cortical 1 hyperaldosteronism,
Cushing’s syndrome
medulla phaeochromocytoma
-Pregnancy
-Drugs esp OCP, HRT






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 (?)
-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 AfricanCaribbeans may have genetic basis








-High body mass index
-High alcohol intake
-High salt intake
-Low potassium intake
-Low fibre/high fat
-Physical inactivity
-Stress
SBP higher by:-
15 mmHg
8 mmHg
5 mmHg
5 mmHg
2-3 mmHg
2-3 mmHg
????





Age being older
Ethnicity African-Caribbean
Family history positive
Body mass Overweight/obese
Alcohol intake high
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
How strong are the relative risks of
high 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
Percent of Population
25
20
90th percentile
15
10
95th percentile
5
0
80
120
100
140
160
180
Systolic Blood Pressure (mm Hg)
Source: NHANES II
200
Stroke Rate per 1,000
Population
12
10
8
6
4
2
0
<120
120-139
140-159
160-179
Systolic Blood Pressure (mm Hg)
Source: Framingham Heart Study, 1980
180+
Mortality From CHD
(No./10,000 Person Years)
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
110
United States
Northern Europe
Mediterranean southern Europe
Inland southern Europe
Serbia
Japan
120
130
140
150
Systolic Blood Pressure (mm Hg)
160
170
(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.
DIES
16 yr Lost
150/100
9 yrs
140/95
4
130/90
120/80
0
10
20
Build/Bp Study: 1935-1954;Metropolitan Life
30
40
50
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










-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?
Population-Based Strategy
SBP Distributions
Before
Intervention
After
Intervention
Reduction in
BP
Reduction in SBP % Reduction in Mortality
mmHg
Stroke CHD Total
2
3
5
-6
-8
-14
-4
-5
-9
-3
-4
-7
Hypertension 1991;17:I-16–I-20.
SOURCES OF DIETARY SALT
Water
1%
Other
Sodium
3%
Table Salt
9%
Cooking Salt
6%
Processed Food
81%
Source: James et al. The dominance of salt in manufactured food in the sodium intake
of affluent societies. Lancet 1987;8530:426-428.



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.

Preventable

Treatable

Controllable

Why is so Difficult to Do?
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%

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
the starting blood pressure
Because the relations of BP and CVD risk are
continuous there is no rational target for BP
reduction (pragmatic targets for patients on
treatment)
Br Hyp Soc SBP <140 DBP < 85 mmHg
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’
Lifestyle Modifications
Modification
Approximate SBP
Reduction
(range)
Weight Reduction
5-10 mmHg/10kg
Adopt DASH eating plan
8-14 mmHg
Dietary sodium reduction
2-8 mmHg
Physical activity
4-9 mmHg
Moderation of alcohol
consumption
2–4 mmHg
Responsibility for a Problem
(Who is to blame?)
Self
Responsibility
for a Solution
(Who will control
the future?)
Self
Other
Other
Moral Model
Compensatory Model
• Person feels lazy
• Person needs motivation
• Person feels deprived
• Person needs power
(skill)
Enlightenment Model
Medical Model
• Person feels guilty
• Person needs discipline
• Person feels ill
• Person needs treatment
* Brickman, American Psychologist 37(4):368–384, April 1982.
Patient believes
– His diagnosis
– Hypertension is serious
– In the efficacy of medicine
– He can control HBP with
doctor’s help.
Patient doesn’t
understand the
difference between
control and cure.
He thinks he’s
“cured”.
Patient receives
no call from
doctor.
Patient cooperates
with doctor, and BP
is controlled.
Patient told, “It’s
okay now.”
Patient receives
no re-education
about the
lifelong need for
treatment.
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.”
Belief that he’s
“cured” and “told to
stop medicine” is
reinforced.
Patient stops
medicine and
visits.
Drops
out
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
medicine is needed
only to lower blood
pressure, not to keep
it low.
Patient has no
symptoms to tell him
that blood pressure is
uncontrolled.
Patient
believes
hypertension
is “nervous
tension.”
Patient believes he
can tell when BP is
high since he
knows when he is
tense.
Medical system
does not follow up
to recall patient for
appointments.
Patient believes he can
control HBP with “selfdiscipline” or by
“accepting life.”
Patient takes
medicine when he
feels tense and
believes this
adequately lowers
BP.
Patient feels no need to
see doctor and keep
appointments because
he knows when to take
medicine.
Patient believes he’s adequately
controlled—reinforced by lack of
professional intervention.
Remains Uncontrolled
Drops
out
• 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.