High blood pressure is a major risk factor for cardiovascular disease

Blood pressure is continuously related to cardiovascular disease. Ischaemic heart disease (IHD) and stroke are the most common consequences of high blood pressure and the most frequent cardiovascular diseases in the population. Every 20 mmHg systolic or 10 mmHg diastolic increase in blood pressure doubles the mortality from IHD and stroke at age 40-69 years and increases IHD and stroke mortality at age 70-89 years by 50% (Lewington et al., 2002). For a more complete overview see Ischaemic heart disease mortality rate and Stroke mortality rate in each decade of age versus blood pressure at the start of that decade.

Estimates from observational research and clinical trials suggest that a 10 mmHg decrease in systolic blood pressure (or 5 mmHg decrease in diastolic blood pressure) reduces the risk of IHD by approximately 20 to 25% and the risk of stroke by 30 to 40% (Lawes et al., 2002; Lawes et al., 2004; also see Interventions). This reduction in risk applies to fatal and non-fatal events, to males and females, and across regions.

The proportional association of blood pressure with IHD and stroke is modified by age. As shown in Age-specific hazard ratios the slope of the association is steepest in younger age and flattens with ageing but remains continuous in higher age groups. Between the ages of 40 and 69 years, each increase of 20 mm Hg SBP or 10 mmHg DBP is associated with a doubling in mortality from stroke, IHD and other vascular disease. Between the ages of 70 and 89 years, there is still a strong relationship between blood pressure and mortality, but the order of magnitude is slightly smaller (1.5-fold increase in vascular mortality with a 20/ 10 mm Hg increase in SBP/DBP) This highlights the importance of early Interventions.

High blood pressure is a major precursor for heart failure and further vascular diseases

High blood pressure increases the risk of heart failure two to threefold and accounts for about half of heart failure burden in the general population (Kannel, 2000; Lloyd-Jones et al., 2002). High blood pressure is linked to heart failure in two ways. Firstly, high blood pressure itself leads to structural and functional impairment of the heart muscle resulting in heart failure. Secondly, high blood pressure is a risk factor for coronary heart disease, and heart failure is a common consequence of coronary heart disease (Meredith & Ostergren, 2006).

High blood pressure also increases the risk of peripheral artery disease, and end stage renal disease (ESH/ESC Task Force, 2007). High blood pressure can further harm blood vessels in the eye and lead to eye disease. In summary, high blood pressure is a major risk factor for an array of cardiovascular diseases.

High blood pressure affects cognitive function

High blood pressure is associated with cognitive impairment. Cognitive decline and dementia occur more frequently in persons with high blood pressure, due in part to the intermediate outcomes of blood pressure, such as cardiovascular disease and in particular stroke (so-called ‘vascular dementia’) (Staessen et al., 2007). Long-term studies show that raised systolic blood pressure in midlife increases the risk of dementia in late-life (Freitag et al., 2006; Kivipelto et al., 2001). High blood pressure not only raises the risk of vascular dementia but appears to be also a risk factor for dementia of Alzheimer’s type (Breteler, 2000; Staessen et al., 2007).

High blood pressure is a major component of global cardiovascular risk

It is important to look at high blood pressure in the context of total cardiovascular risk. In the majority of cases, high blood pressure is accompanied by other risk factors. See Ischaemic Heart Disease- Causes and risk factors for an overview of these other risk factors. The various risk factors for cardiovascular disease interact and together determine the total cardiovascular risk. As can be seen from Absolute risk of cardiovascular disease over 5 years, the absolute risk for otherwise healthy individuals is small, even at a very high systolic blood pressure level, but increases dramatically with the presence of additional risk factors. Therefore, high blood pressure should not be regarded as an isolated risk factor but in the context of other risk factors.

High blood pressure may be responsible for half of disease burden from coronary heart disease and stroke

Globally, about 47% of IHD and 54% of strokes may be attributable to suboptimal systolic blood pressure exceeding 115 mmHg (Lawes et al., 2008). Estimates from INTERHEART, a worldwide case-control study on coronary heart disease, indicate that 22% of IHD in Western Europe and 25% of IHD in Central and Eastern Europe may be due to a history of high blood pressure(Yusuf et al., 2004). The reliability of these data is, however, limited, both because high blood pressure in this study was self-reported rather than measured and because the case-control design is prone to bias.

Data from 600,000 participants in the Asia-Pacific Cohort Studies Collaboration, using the common hypertension definition of blood pressure >140/ 90 mmHg, reveal that 4 to 28% of IHD in men and 8 to 39% in women may be caused by hypertension. The corresponding ranges for haemorrhagic and ischaemic stroke among males were 18 to 66% and 8 to 44%, and 15 to 49% and 12 to 45% in females (Martiniuk et al., 2007). It should be noted, however, that these data cannot be directly translated to the European region, due to differences in hypertension prevalence, disease incidence and stroke subtypes.

High blood pressure is the leading risk factor for mortality worldwide

High blood pressure is the most important risk factor in terms of attributable mortality worldwide. Estimates from the WHO GBDS indicate that approximately 13% of global mortality may be attributed to high blood pressure translating into more than 7 million deaths per year (Lopez et al., 2006).

In developed countries, the impact of high blood pressure on mortality is estimated to be even more important. According to the GBDS, 20.1% of deaths among males and 23.9% among females in the European region and other developed countries may be due to high blood pressure (WHO, 2002d). Mortality attributed to high blood pressure is equally distributed between males and females (49 vs. 51%) and occurs mainly in older age (81% at age 60 years and older vs. 19% at age 15-59 years) (Rodgers et al., 2004).

High blood pressure is a leading cause of loss of healthy life

In terms of DALYs, an indicator for loss of healthy life, high blood pressure is the second major cause of disability worldwide next to childhood underweight (Lopez et al., 2006).

The GBDS estimates that 5.6% of DALYs in low-and middle income countries and 9.3% in high-income countries are attributable to high blood pressure. Estimations for the WHO European Region show that high blood pressure is the leading cause of disability in this region accounting for 12.8% of total DALYs (WHO, 2002d). See also Shares of seven leading risk factors in the DALY burden.

The majority of disease burden from suboptimal blood pressure occurs in the middle age-groups

A study analysing the global disease burden from systolic blood pressure greater than 115 mmHg estimates that approximately two thirds of the disease burden occurs in the age-group 45-69 years (Lawes et al., 2006). About half of this disease burden occurs in individuals with systolic blood pressure levels between 130 and 150 mmHg.