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Large swings in blood pressure could kill

SINGAPORE — Blood pressure naturally rises and falls slightly over the day, depending on what you do and eat. But waking up to higher-than-normal readings and see-sawing blood pressure during the day could spell trouble if you have hypertension, new findings based on over 21,000 patients in Japan show.

A device monitoring patients' vital signs, like blood pressure, heart/pulse rate and skin temperature, which will alert nurses of abnormalities. TODAY file photo

A device monitoring patients' vital signs, like blood pressure, heart/pulse rate and skin temperature, which will alert nurses of abnormalities. TODAY file photo

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SINGAPORE — Blood pressure naturally rises and falls slightly over the day, depending on what you do and eat. But waking up to higher-than-normal readings and see-sawing blood pressure during the day could spell trouble if you have hypertension, new findings based on over 21,000 patients in Japan show.

Some previous studies have suggested that large swings in blood pressure are unimportant as long as they average out.

But in the Japanese study, patients with exaggerated blood pressure surges in the morning faced a 2.7 times higher risk of getting stroke than those whose hypertension were kept fairly stable, said the Professor Kazuomi Kario from the Jichi Medical University School of Medicine at the Asian-Pacific Congress of Hypertension earlier this month.

The findings, published in the Journal of Clinical Hypertension in August, prompted researchers to call for solutions to improve hypertension management in the region.

Prof Kario is one of the study’s authors from the HOPE Asia network, made up of 12 representatives in Asia including Singapore, which hopes to conduct the study here.

One of the leading preventable causes of premature death worldwide, hypertension affected an estimated 1.4 billion people in 2010. In Singapore, it is one of the top chronic diseases.

About one in four adults (23.5 per cent) here have high blood pressure, compared to 11.3 and 17.4 per cent for diabetes and high cholesterol respectively, according to the 2010 National Health Survey.

High blood pressure creates added force against the artery walls. Over time, this extra pressure can damage the arteries, making them more vulnerable to narrowing and plaque build-up, Prof Kario said.

Surges and large fluctuations in blood pressure are particularly dangerous as changes in the pressure on blood vessel walls can loosen and eventually break off pieces of plaque.

“These broken-off pieces of plaque can then travel through the circulatory system and cause blockages in smaller blood vessels and, depending on where they lodge, cause strokes or damage the heart and/or kidneys,” said Prof Kario.

There are often no signs to show whether one’s blood pressure is well-controlled or not.

Up to one in two patients do not know they have hypertension until they measure their blood pressure, said Professor Tay Jam Chin, senior consultant of the department of general medicine at Tan Tock Seng Hospital and one of the study authors.

Hypertension may not be picked up during healthcare visits, said Dr Kario.

“These patients are rested from sitting in the waiting room. If they are doing other tests, they may even have fasted, which can temporarily lower blood pressure,” he said.

RETHINK YOUR SALTY DINNER

Blood pressure spikes and fluctuations may occur due to a variety of reasons. For instance, eating a salty dinner can increase one’s risk of morning blood pressure surge, said Dr Kario. So can smoking, excessive consumption of alcohol in the long term, sleep apnoea and other chronic conditions such as obesity, diabetes and chronic kidney disease.

Asians, in particular, tend to have greater morning blood pressure surges than Caucasians.

A known cause of this is genes. Many Asians are more sensitive to salt due to a variation in a hormone system known as the renin-angiotensin-aldosterone system, which regulates plasma sodium concentration and blood pressure in the arteries, Prof Kario said.

“As well as being more sensitive to salt, many Asians consume a lot of salt because of the heavy use of soy and other sauces in Asian cuisine. Other factors could be the rising incidence of obesity and many urban-dwelling Asians report very high-stress levels,” said Dr Kario.

Not taking anti-hypertensive medications as prescribed or inadequate use of medications may also affect blood pressure control.

“Some medications are not truly long-acting. The blood pressure-lowering effect may start to tail off when it is taken once a day, so by the end of the day or next morning, blood pressure starts to creep upward,” said Dr Chee Tek Siong, a member of the Singapore Heart Foundation’s board of directors.

In such cases, large surges in morning blood pressure may be minimised by using anti-hypertensives with longer-acting effect, said Dr Chee. Sometimes, the doctor may spread out the medications.

MONITOR BLOOD PRESSURE AT HOME

In the study, Prof Kario’s team suggested home blood pressure monitoring as a way to achieve steady 24-hour control.

This can be done by obtaining a home blood pressure set and recording readings in a notebook or electronically, said Prof Tay. The latest generation of smart monitors can be connected to smartphones and other mobile devices, and linked up to caregivers and doctors, said Prof Kario.

The method has been shown to detect hypertension more accurately than having blood pressure taken in the clinic, said Dr Chee.

It also provides a more complete picture of the patient’s condition and ensures he gets the appropriate treatment. Patients who are monitored at home experienced 25 and 27 per cent fewer fatal heart and stroke events, respectively over the course of the trial, according to the study.

“If the patient is having morning surges after rising and before he takes his morning medication, the doctor can spot it and either switch his medication to before bedtime or split the dose for a more sustained effect,” said Prof Kario.

Patients who do home monitoring play a more active role in managing their conditions and are more compliant with taking prescribed medications, said the experts.

Despite its benefits, home monitoring is not routinely used to diagnose or manage hypertension in Singapore. Aside from the need to train primary care doctors to teach and encourage patients to use the device, patients also need to be convinced.

The price of a home blood pressure monitoring set, available at community and hospital pharmacies, starts from S$100. There are currently no government subsidies for it, said Prof Tay.

“We are hoping that prices will decrease over time,” he said.

Home monitoring, however, may not be suitable for some patients, such as those with irregular heart rhythm, a very anxious character or hand weakness that makes it difficult to put on a blood pressure cuff.

HOW TO USE A HOME BLOOD PRESSURE MONITOR CORRECTLY

Dr Chee Tek Siong, a member on the board of directors for the Singapore Heart Foundation, offers these tips:

1. Use an upper-arm blood pressure monitor for home monitoring. Use monitors that are validated by a professional organisation such as the British Hypertension society or American Heart Association.

2. The size of the blood pressure cuff must fit you well, and not be too small or too big.

3. Rest for at least five minutes before measurement. Do not smoke, eat or exercise half an hour before measurement.

4. Be still and do not talk while measuring your blood pressure.

5. Sit comfortably on a chair without crossing the legs. You should be able to rest both feet on the ground while sitting on the chair.

6. Do not wear clothing with tight sleeves.

7. Measure twice a day: Once in the morning within one hour of waking, before breakfast and before taking morning medications, and in the evening or before bedtime.

8. Take two readings at one to two minutes apart each time (this means taking a total of four readings per day). It is preferable to take readings for five or seven consecutive days. Exclude the readings on the first day and average out the remaining readings.

A normal blood pressure reading should be <135/85 mmHg. Some authorities advocate <125/75 mmHg for diabetics and those with kidney failure.

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