Depression and extremes of blood pressure predict highest rates of harmful vascular events

The study in more than 35,000 patients found that the risk of further stroke or heart attack, heart failure or dying due to heart disease at four years was 83% higher in depressed patients with high blood pressure and 36% higher in depressed patients with low blood pressure, compared to those with normal blood pressure and no depressive symptoms.

"Previous studies have shown that patients with existing heart disease, diabetes or stroke are more likely to suffer from further heart attack or stroke than the general population, particularly those who have extremes of blood pressure or have depressive symptoms but until now the effects of having both together were unknown," said Dr Jani. "This is the first study which has specifically investigated the relationship between depressive symptoms and extreme blood pressure in influencing the rate of heart attack, stroke, heart failure and heart disease related deaths in patients with existing heart disease, diabetes or stroke."

The study included 35 537 community dwelling patients with existing heart disease, diabetes or stroke from Scotland, UK. In 2008-09 depression was assessed using the hospital anxiety and depression score (HADS-D). Systolic (SBP) and diastolic (DBP) blood pressure were recorded and patients were classified as very high (SBP>160, DBP>100), high (SBP 140-159, DBP 90-99), normal (SBP 130-139, DBP 80-89), tightly controlled (SBP 120-129, DBP 80-84) or low (SBP<120, DBP<80) blood pressure. The occurrence of major harmful events (further stroke or heart attack, heart failure or dying due to heart disease) was recorded over a period of four years.

During the four year follow up period 3 939 patients (11%) had a least one major harmful event. Depression had a significant interaction with SBP (p=0.03) in predicting a major harmful event. Dr Jani said: "The relationship between depression and blood pressure is an area of ongoing medical research and various physiological theories are under review to explain the nature of this relationship."

Patients with the combination of high blood pressure and depressive symptoms had 83% higher risk of a major harmful event at four years (hazard ratio (HR) =1.83; 95% confidence interval (CI) 1.46-2.30, p<<0.001) and those with low blood pressure and depressive symptoms had a 36% higher risk (HR=1.36; CI=1.15-1.62, p<0.001) than those with normal blood pressure and no depressive symptoms. The results were adjusted for factors that can influence risk of vascular events such as age, sex, body mass index (BMI), total cholesterol levels, socioeconomic status, use of antidepressants and the number of existing medical conditions.

"In our study, patients with a combination of depression and high or low blood pressure had the highest rate of a major harmful vascular event at four years," said Dr Jani. "One explanation for our results may be that these patients had the most severe form of existing heart disease, diabetes or stroke, which was not recognised and hence had the worst outcomes."

He concluded: "Our findings suggest that focusing resources on monitoring blood pressure and providing treatment in patients with associated depressive symptoms could improve health outcomes by reducing the risk of further strokes or heart attacks, having heart failure or dying from heart disease. They also indicate that patients with high or low blood pressure might benefit from screening and treatment for depression. To date there are no studies showing that treatment of depression changes or improves cardiovascular outcomes and more research is needed in this area. Studies are also needed to further understand how blood pressure and depression interact."