High blood pressure is caused by underlying disease in minority of cases

In 95% of cases no identifiable cause of high blood pressure is found and the condition is diagnosed as ‘essential hypertension’. In the vast minority of cases (between 2% and 5%), particular diseases such as kidney disease or adrenal disease cause hypertension and the condition is labelled ‘secondary hypertension’ (Messerli et al., 2007). For a complete overview see the list of identifiable causes of hypertension.

If the cause cannot be identified, high blood pressure may be due to an unfavourable lifestyle or particular risk factors.

Age is a major determinant of high blood pressure

In westernised societies, blood pressure progressively increases with ageing beginning in childhood. Systolic blood pressure increases linearly with age whereas diastolic blood pressure peaks at age 50 to 60 years and declines in later life (Franklin et al., 1997). Also see: Mean systolic and diastolic blood pressures.

The age-related pattern of blood pressure is seen in both men and women, but there is a gender difference, with women starting at a lower blood pressure level than men and catching up by the sixth decade. Given the age dynamics of blood pressure, 50 to 80% of the European and North American population aged 65 to 74 years can be classified as hypertensive using the 140/90 mmHg threshold (Wolf-Maier et al., 2003). Also see: Hypertension prevalences by age group.

Data from the Framingham Heart Study indicate that the residual lifetime risk of hypertension in middle-aged individuals without evidence of high blood pressure is 90% (Ramachandran et al., 2002).

The age-related increase in systolic blood pressure is mainly responsible for increasing incidence and prevalence of high blood pressure with ageing (Franklin et al., 1997). Systolic hypertension is the predominant form of hypertension in middle-aged and elderly individuals (Franklin et al., 2001).

Therefore, from age 50 onwards, systolic blood pressure is the more powerful cardiovascular risk factor, whereas diastolic blood pressure is more important in the younger population.

Physical inactivity and overweight promote high blood pressure

Several lifestyle related factors have been identified as important risk factors for high blood pressure.

Physical exercise and body weight have an influence on blood pressure level. There is sound evidence that physical activity contributes to a reduction of blood pressure (Whelton et al., 2002; Cornelissen & Fagard, 2005). Overweight and obesity are important risk factors for high blood pressure. An increase in body mass index leads to an increase in both systolic and diastolic blood pressure (Drøyvold et al., 2005; Wilsgaard et al., 2000; Gelber et al., 2007).

Unhealthy diet contributes to high blood pressure

Dietary components, particularly insufficient fruit and vegetable intake, high consumption of saturated fat, low fish intake, and high sodium and low potassium intake are related to high blood pressure. Dietary patterns based on the so-called DASH diet, a diet rich in fruits, vegetables and low-fat dairy products, have proven to lower blood pressure (Sacks et al., 2001). Epidemiological studies suggest that dietary salt intake is directly related to blood pressure elevation (WHO/FAO, 2002). Increased fish intake (or supplementation of fish oil) have been shown to lower blood pressure (Dickinson et al., 2006; Bao et al., 1998). Coffee consumption may slightly increase blood pressure (Noordzij et al., 2005), but long-term effects on hypertension incidence seem to be very small (Uiterwaal et al., 2007; Hu et al., 2007).

Alcohol consumption increases blood pressure

Alcohol consumption is directly associated with blood pressure. The relationship between alcohol intake, blood pressure level, and hypertension prevalence in populations is almost linear ( Puddey et al., 1997, Keil et al., 1998). While drinking light to moderate amounts of alcohol has been shown to be protective in terms of cardiovascular mortality (see Positive effects of low-level alcohol consumption), higher alcohol intake leads to excess mortality and is a cardiovascular risk factor (Rimm et al., 1999, Corrao et al., 2000).

Until recently there was a general consensus that light to moderate amounts of regular alcohol consumption do not seem to have a negative impact on blood pressure (Marmot et al., 1994, Fuchs et al., 2001), but this finding has been questioned in a recent study (Chen et al., 2008). Binge drinking, or drinking high amounts of alcohol at one occasion, has, however, been associated with a particularly high risk of stroke reflecting a substantial blood pressure increase (ESH/ESC Task Force, 2007).

Impact of stress and psychosocial factors on high blood pressure is not yet clear

The relationship between stress, psychosocial factors and high blood pressure is complex and not yet fully understood. However, a growing body of evidence suggests that psychosocial factors play a role in the development and onset of high blood pressure (Kaplan & Nunes, 2003). For example, blood pressure reactions to stress can predict future blood pressure elevation (Carroll et al., 2003, Carroll et al., 2001). Depression can also be predictive of hypertension development (Davidson et al., 2000, Jonas et al., 1997, Jonas & Lando, 2000), as can exposure to noise, which is also a known stressor. Recent studies showed that blood pressure increases with exposure to road traffic noise (Bluhm et al., 2007, De Kluizenaar et al., 2007), occupational noise (Sbihi et al., 2008), and aircraft noise (Eriksson et al., 2007, Haralabibis et al., 2008).

Genetic determinants of high blood pressure are unclear

Some genetic abnormalities associated with rare types of hypertension have been identified recently. Despite these findings, genetic abnormalities have not been found to be responsible for an appreciable proportion of the burden of high blood pressure in the population (US Department of Health and Human Services, 2004).

Impact of lifestyle on hypertension prevalence is substantial

Population-based data from selected countries (Finland, Italy, the Netherlands, United Kingdom, and USA) have been used to estimate the burden of hypertension attributable to overweight, dietary components, and physical activity (Geleijnse et al., 2004). Overweight was the most important contributor to hypertension in all countries except Italy (range 11-25% of hypertension due to overweight depending on country). If the effects of additional risk factors are taken into account, around 40% of hypertension prevalence (depending on the population) can be subscribed to overweight, diet, and physical inactivity. It should, however, be noted that these data are based on estimations that have been derived from simplified models. While the findings of this study should therefore be interpreted with caution, they do indicate that selected lifestyle factors have a major impact on hypertension prevalence in populations.