Rapsomaniki E, Timmis A, George J, et al. Blood pressure and incidence of twelve cardiovascular diseases: Lifetime risks,
healthy life-years lost and age-specific associations in 1.25 million people. Lancet
2014;383:1899–911.
The associations of blood pressure with the different clinical presentations of incident
cardiovascular diseases in a contemporary population have not been studied thoroughly.
Twelve different presentations of cardiovascular disease were analysed for associations
with blood pressure in this study published in the Lancet 2014.
Electronic health records from 1997 to 2010 in the CALIBER (CArdiovascular research
using LInked Bespoke studies and Electronic health Records) programme, from 225 primary
care practices registered with it, were used to set up a cohort of 1.25 million patients,
30 years of age or older and initially free from cardiovascular disease, 20% of whom
received blood pressure-lowering treatments. The heterogeneity in the age-specific
associations of clinically measured blood pressure with 12 acute and chronic cardiovascular
diseases were studied, and estimated lifetime risks (up to 95 years of age) and cardiovascular
disease-free life years lost adjusted for other risk factors at index ages 30, 60
and 80 years were calculated. Patients’ blood pressure was measured at initial presentation
at primary care clinic closest to index date, and they were classified as hypertensive
at a blood pressure higher than 140/90 mmHg. Isolated systolic hypertensio (>140 mmHg)
and isolated diastolic hypertension (>90 mmHg) were also noted. The cardiovascular
diseases recorded were stable and unstable angina, myocardial infarction, unheralded
coronary artery disease death, heart failure, sudden cardiac death, transient ischaemic
attack, ischaemic stroke, subarachnoid haemorrhage, intracerebral haemorrhage, peripheral
arterial disease and abdominal aortic aneurysm.[1] Unclassified stroke was considered an ischaemic stroke, as 87% of all unclassified
strokes have been shown as ischaemic origin in previous studies.[2]
During 5.2 years median follow-up, 83098 initial cardiovascular disease presentations
were recorded. In each age group, the lowest risk for cardiovascular disease was in
people with systolic blood pressure of 90-114 mmHg and diastolic blood pressure of
60-74 mmHg, with no evidence of a J-shaped increased risk at lower blood pressures.
Associations with high systolic blood pressure were highest for intracerebral haemorrhage
(hazard ratio 1.44 [95% CI 1.32-1.58]), subarachnoid haemorrhage (1.43 [1.25-1.63]),
and stable angina (1.41 [1.36-1.46]) and weakest for abdominal aortic aneurysm (1.08
[1.00-1.17]). Higher systolic blood pressure had a greater effect on angina, myocardial
infarction and peripheral arterial disease, while raised diastolic blood pressure
had a greater effect on abdominal aortic aneurysm. Pulse pressure associations were
strongest for peripheral arterial disease (1.23 [1.20-1.27] and inverse for abdominal
aortic aneurysm (HR per 10 mmHg 0.91 [95% CI 0.86-0.98])). People with hypertension
(blood pressure ≥ 140/90 mmHg or those receiving blood pressure-lowering drugs) had
a lifetime risk of overall cardiovascular disease at 30 years of age of 63.3% (95%
CI 62.9-63.8) compared with 46.1% (45.5-46.8) for those with normal blood pressure
and developed cardiovascular disease 5.0 years earlier (95% CI 4.8-5.2). Stable and
unstable angina were responsible for most (43%) of the cardiovascular disease-free
years of life lost associated with hypertension from index age 30 years, whereas heart
failure and stable angina accounted for the largest proportion (19% each) of years
of life lost from index age 80 years.
The widely held assumptions that blood pressure has strong associations with the occurrence
of all cardiovascular diseases across a wide age range, and that diastolic and systolic
associations are concordant are not supported by the findings of this high-resolution
study.[1] The assumption that “lower is better” for blood pressure in relation to vascular
events and mortality in patients with vascular disease may not be true. This can be
ascribed to a J-curved relationship between blood pressure and cardiovascular events.
The Secondary Manifestations of Arterial Disease (SMART) Study followed up 5788 patients
with symptomatic vascular disease for new vascular events (i.e. myocardial infarction,
stroke or vascular death) and all-cause mortality. During a median of 5.0 years (interquartile
range: 2.6-8.1 years), 788 patients experienced a new vascular event, and 779 died.
Overall, the covariate adjusted relationship between mean baseline systolic, diastolic
or pulse pressure, and the occurrence of vascular events followed a J-curve with increased
event rates above and below the nadir blood pressure of 143/82 mmHg. A similar non-linear
relationship was found for diastolic pressure and all-cause mortality. Elevated blood
pressure was not associated with increased morbidity and mortality in patients with
recently diagnosed coronary artery disease, 65 years, and pulse pressure of 60 mmHg.
The authors note that low blood pressure could also be a symptom rather than a cause
of disease, especially in this subgroup. Blood pressure level below and above 143/82
mmHg was found as an independent risk factor for recurrent events in patients with
manifest vascular disease in this study.[3] The lifetime burden of hypertension is enormous, notwithstanding modern treatment.
Both studies emphasize the need for new blood pressure-lowering strategies in light
of these findings and further randomized trials to assess their impact on human lives.
