People in their thirties may risk a heart attack or stroke in later life even when they have 'normal' blood pressure, if it's too high or steeply rising, according to a new study led by UCL researchers.
The study, funded by the British Heart Foundation and published in the journal Circulation: Cardiovascular Imaging, found that people with higher blood pressure in their thirties and forties, as well as in the three decades after that, had reduced blood flow to their heart muscle - which pumps blood around the body - at the age of 77.
The more years people spent with higher blood pressure, and the more sharply it rose, the larger the reduction in blood flow to their heart. This reduced blood flow was found to be linked to a greater risk of having a heart attack, stroke or heart failure in later life.
The risk from higher or fast-rising blood pressure was seen from as young an age as 36, even if people didn't meet the current criteria for a diagnosis of 'high' blood pressure.
The researchers say their findings illustrate the need for people to get regular blood pressure checks years before they hit middle age.
Rather than intervening only when people are diagnosed with high blood pressure, they say doctors should track people's long-term patterns and watch out for people who have 'normal' blood pressure which is rising steeply. These people could be offered advice to change their lifestyles, such as through diet and exercise, or be given medications to bring their blood pressure under better control.
Senior author Dr Gaby Captur (UCL Institute of Cardiovascular Science and the Royal Free London NHS Foundation Trust) said: "Small, steady increases in blood pressure through adulthood, even if you have a 'normal but high' reading, can be quietly damaging the heart, long before symptoms appear. Your blood pressure in your thirties, we found, can affect the heart 40 years later.
"We've shown that lifelong blood pressure control is an investment in how well the heart ages. Our hearts remember decades of blood pressure exposure. Therefore, protecting heart health must start while you're young, before blood pressure begins to creep up."
Blood pressure is the pressure of blood in the arteries that carry blood from the heart to the rest of the body. While some pressure is needed to get blood moving, consistently high levels can damage and stiffen arteries, making it easier for fatty deposits to build up in blood vessel walls. This build-up - known as atherosclerosis - can narrow blood vessels and reduce blood flow to the heart, which can trigger a heart attack, or a stroke if the blood supply to the brain is affected.
The new study, called MyoFit46, recruited 505 participants from a group of people born during one week in March 1946, who are part of the National Survey of Health and Development study. This study has followed thousands of people over decades, taking blood pressure readings at the ages of 36, 43, 53, 62, 69 and 77.
Having higher blood pressure at all of these ages was linked to poorer blood flow to the heart muscle in later life. The blood flow was measured when the study volunteers were aged 77, using a detailed heart scan called a stress perfusion cardiovascular magnetic resonance (CMR) scan.
Blood pressure is recorded using two numbers. The first number, which is higher and is called systolic blood pressure, is the pressure against the arteries when the heart is pumping blood around the body. The second and lower number is diastolic blood pressure - the pressure in the arteries when the heart relaxes between beats.
In the study, every 10-point increase in someone's systolic blood pressure - for example, from 120 to 130mmHg - between the ages of 36 and 69 was linked to up to a six per cent reduction in blood flow to their heart at age 77.
But the largest impact was seen for people within a critical time window between the ages of 43 and 63, when their systolic blood pressure rose from 120 to 140mmHg. Every 10-point rise in blood pressure here was linked to a nine to 12 per cent reduction in blood flow to the heart aged 77.
A systolic reading between 120 and 140mmHg would typically fall short of high blood pressure, which doctors call hypertension. However, doctors may describe this as 'pre-hypertension' and it is seen as the higher end of normal blood pressure, when people should consider making lifestyle changes including to their diet and activity levels.
The study, which tracked people's health using their health records and regular questionnaires, found every one per cent reduction in blood flow to the heart was linked to a three per cent higher risk of a major cardiac event - a heart attack, stroke or heart failure.
The more years of their life people spent with higher blood pressure, the greater the apparent impact in later life.
Results showed that if someone's systolic blood pressure blood pressure increased by 10mmHg and remained at that higher level from the age of 36 to 77, their heart's blood flow would be up to 11 per cent lower at the age of 77. This reduction was linked to a 33 per cent higher chance of having a major cardiovascular event.
How steeply someone's blood pressure rises over the years also appears to be important. For someone aged 36, if their systolic blood pressure rose by one point every year up to the age of 43, the blood flow to their heart would be two per cent lower at the age of 77.
People whose systolic blood pressure increased by one point each year between the ages of 53 and 63 would have a five per cent reduction in their heart's blood supply, according to the results.
This was the case even when researchers took into account factors like people's age, sex, body size, social class, smoking, exercise levels and other conditions such as diabetes, which could skew the link between blood pressure and heart health. They also factored in people's blood pressure when their heart was scanned aged 77.
Even people with well-controlled blood pressure at 77 saw effects apparently caused by higher blood pressure at younger ages.
Currently, people are recommended to start medication for high blood pressure if their systolic reading is over 140 (or over 130 if they have pre-existing cardiovascular disease). But researchers say keeping blood pressure below 120 may be helpful in maintaining vital blood flow to the heart in later years.
Next, they hope to start clinical trials to see if monitoring people's blood pressure trajectories from the age of 18, rather than solely relying on one-off clinic measurements, and prescribing treatment accordingly, could help to reduce people's risk of having a heart attack or stroke.
Professor Bryan Williams, based at UCL Institute of Cardiovascular Science and also Chief Scientific & Medical Officer at the British Heart Foundation, said: "Blood pressure is a silent killer, and the most important cause of heart attacks, strokes and early death in the UK each year.
"The reason we refer to blood pressure as the silent killer is that it is usually symptomless and blood pressure levels creep up gradually, so the only way of being sure you don't have high blood pressure is to get it checked.
"This interesting research suggests that we should be encouraging people to get regular blood pressure checks from a younger age, when it is often much easier to control.
"It should also prompt us doctors to reconsider whether we should be recommending earlier lifestyle changes or medication to bring people's blood pressure back under control as soon as it becomes elevated, to provide longer term health benefits."
Dr Cristian Topriceanu, PhD Fellow at UCL Institute of Cardiovascular Science and first author of the study, said: "By tracking blood pressure from people's mid-thirties to their late seventies, we've found that it's not just how high your blood pressure is, but also how fast it rises over time, that predicts how well, or how poorly, blood is able to flow to the heart in your later years.
"This gives doctors a new way to think about risk - by looking at blood pressure trajectories, not just one-off readings. Spotting and treating those changes earlier could help doctors spot those at risk of heart attacks, strokes, and heart failure in later life."
The research is in the running for the Melvin Judkins Early Career Clinical Investigator Award Competition of the American Heart Association Council on Cardiovascular Radiology and Intervention, where it is due to be presented during the upcoming Scientific Sessions conference in New Orleans.
