Studies show that caffeinated coffee can acutely increase blood pressure, but decaffeinated coffee does not. Caffeine seems to be a major factor in affecting blood pressure, and experts suggest that as such, it is also a trigger for cardiovascular events.
However, people who consume coffee and caffeine regularly are not thought to face such a risk, because they develop a tolerance. This suggests that the intervals at which people drink coffee are of some significance.However, for occasional rather than regular consumers, it might be a different story.
How does coffee affect a blood pressure test?A team from Western University and Lawson Health Research Institute in London, Ontario, in Canada, came up with some surprising results when they measured the effect of occasional coffee consumption on blood pressure, and especially how coffee consumption impacts the action of calcium channel blockers.
Calcium channel blockers are a type of medication for lowering blood pressure. They are commonly prescribed for patients with hypertension. Calcium channel blockers, such as felodipine, relax and widen the blood vessels, making it easier for blood to flow. In this way, they reduce blood pressure.
Led by Dr. David Bailey, a Lawson Scientist and researcher at Western’s Schulich School of Medicine and Dentistry, the team wanted to find out what would happen to the blood pressure if a person abstained from caffeine long enough to eliminate the caffeine from the blood.They expected to see a higher blood pressure the next time a person drank coffee, because eliminating caffeine and then consuming it again could cancel out the pressure-lowering effects of felodipine.
Meanwhile, a late-night meal keeps the body on ‘high alert’ when it should be winding down, researchers found.Heart experts last night advised that adults should never eat within two hours of bedtime – and ideally nothing after 7pm.In a healthy person, blood pressure drops by at least 10 per cent when they go to sleep.
But the results of a study of more than 700 people with high blood pressure found that eating within two hours of bedtime meant their levels stayed high.Experts think this is because eating releases a rush of stress hormones when the body should be starting to relax.People who do not see their blood pressure fall at night are known as ‘non-dippers’ – and have a much higher rate of heart-related death.
Late eaters were nearly three times more likely to be non-dippers, the Turkish researchers found.Meanwhile, the study in nearly 30 000 patients with a prior heart attack found that the risk of a second event was 36 per cent lower for those in the highest income quintile compared to the lowest and increased by 14 per cent in divorced compared to married patients.
Lead author Dr. Joel Ohm, a physician at the Karolinska University Hospital and Karolinska Institutet in Stockholm, Sweden, said: “Are you rich or poor? Married or divorced? That might affect your risk of a second heart attack or stroke. Advances in prevention and acute treatment have increased survival after heart attack and stroke over the past several decades. The result is that more people live with cardiovascular disease – in Sweden almost one fifth of the total population is in this group.”
Most research on cardiovascular prevention is based on healthy people and it is unclear if the findings apply to patients with established disease. An association between socioeconomic status in healthy individuals and future cardiovascular disease was found in the 1950s. This study investigated the link between socioeconomic status in patients who had survived a first heart attack and the risk of a second heart attack or a stroke.
The study included 29 953 patients from the Swedish nationwide registry, Secondary Prevention after Heart Intensive Care Admission (SEPHIA), who had been discharged approximately one year previously from a cardiac intensive care unit after treatment for a first myocardial infarction. Data on outcome over time and socioeconomic status (defined as disposable income, marital status and level of education) was obtained from Statistics Sweden and the National Board of Health and Welfare.
During an average follow up of four years, 2405 patients (eight per cent) suffered a heart attack or stroke. After adjusting for age, gender, smoking status, and the defined measures of socioeconomic status, being divorced was independently associated with a 14 per cent greater risk of a second event than being married. There was an independent and linear relationship between disposable income and the risk of a second event, with those in the highest quintile of income having a 36 per cent lower risk than those in the lowest quintile. A higher level of education was associated with a lower risk of events but the association was not significant after adjustment for income.
Drinking coffee after a break raises blood pressure
To test their theory, they invited 13 people with an average age of 52 with normal blood pressure to participate in an experiment.They carried out three tests on the subjects, separated in time by one week. Before each test, the people consumed no coffee, caffeine-containing products, or other items such as alcohol, grapefruit, marmalade, tobacco, and medications for 48 hours.
At intervals of a week, the participants then took the following, and then they had their blood pressure taken:
*Two 300 milliliter cups of black coffee
*The maximum recommended dose of felodipine (10 mg)
*The coffee plus a dose of felodipine.
Results showed that, after the participants avoided coffee for only two days, enough caffeine was eliminated from the body so that the next time they drank coffee, their blood pressure rose.
After just one cup of coffee, the participants in the coffee-only group experienced the greatest increase in blood pressure. The blood pressure rose within an hour after drinking the coffee, and it lasted for several hours.
Combining coffee with felodipine led to higher levels of blood pressure than taking only felodipine. This could be because the caffeine blocks the positive effect of the drug on the blood vessels, the researchers say.
They note that a morning cup of coffee could affect the diagnosis and treatment of hypertension, or high blood pressure.“Even one cup of coffee containing a relatively low amount of caffeine remarkably compromised the anti-hypertensive effect of this drug at the maximum recommended dose. If you wanted to overcome the effect of the coffee, you had to double the dose of this anti-hypertensive drug which could increase the risk of unwanted excessive drug effects, particularly during the period when coffee is not consumed.”
Bailey is concerned that if a patient drinks coffee just before visiting their doctor, it could complicate diagnosis and treatment. The acute increase in blood pressure could lead to over-prescription of antihypertensive drugs.
He points out that between 15 and 20 percent of people who drink coffee do so only occasionally. People who drink coffee twice a week or less may have an occasional rise in blood pressure. In some people, the rise can be greater than in others.Bailey notes that national and international guidelines regarding high blood pressure do not take into account the impact of coffee, probably because of a lack of evidence.
He hopes that further studies will provide more data, and that occasional coffee drinkers will become more aware of the risks they face.Ohm said: “Our study shows that in the years following a first myocardial infarction, men and women with low socioeconomic status have a higher risk of suffering another heart attack or stroke. This is a new finding and suggests that socioeconomic status should be included in risk assessment for secondary prevention after a heart attack. Even though health care providers are unlikely to keep track of their patients’ yearly salary, simple questions about other socioeconomic variables such as marital status and educational level could make a difference.”
According to the widely used assessment tools for cardiovascular risk, survivors of heart attacks are at the highest possible risk for subsequent events regardless of other risk factors. There is, for example, no difference in estimated risk level between a previously healthy 40-year old female from Spain and a heavily smoking, obese, elderly man with diabetes and high blood pressure from Finland.
Ohm said: “Risk assessment tools are designed for individuals without previous cardiovascular disease and the calculations may not apply to patients with established cardiovascular disease. Socioeconomic status is perhaps a better marker to assess risk of future events in heart attack patients and more research is needed to determine other factors that could be included, such as occupation or residential area.”
Researcher Dr Ebru Özpelit, presenting her results at the speaking at the ESC congress in Rome, said: “If we eat late at night, the body essentially remains on high alert as during the day, rather than relaxing for sleep.“Stress hormones are secreted, causing blood pressure not to decrease during sleep, which should normally happen.”
Özpelit, from Dokuz Eylül University in Turkey, tracked 721 on people diagnosed with high blood pressure, with an average age of 53.She found that those who ate within two hours of going to bed were 2.8 times more likely to retain high blood pressure overnight.People with hypertension are already at a higher risk of heart disease, but if their blood pressure does not fall at night, that risk increases to a far higher level.
Özpelit said: “It is more dangerous. If blood pressure doesn’t drop by more than 10 per cent this increases cardiovascular risk and these patients have more heart attacks, strokes and chronic disease.”
But even healthy people with normal blood pressure should take note of the findings, Özpelit said.“How we eat may be as important as what we eat,” she said.
She advised that people do not skip breakfast, eat lunch, and keep dinner to a small meal.“Eating breakfast and lunch is important but dinner must not be later than seven o’clock in the evening,” she said.The findings add to a growing body of evidence which suggests keeping all meals to within a fixed period of time – and fasting at night – can have a wide range of health benefits.
Previous research has found that an early dinner reduces the risk of breast cancer, lowers blood sugar levels, and helps burn off calories.Experts think part of the reason is that the body evolved to expect meals much earlier in the day – because people went to sleep when it got dark.Özpelit said the invention of electricity changed that – introducing ‘erratic’ eating patterns.
“With the advent of affordable artificial lighting and industrialization, modern humans began to experience prolonged hours of illumination every day and resultant extended consumption of food,” she said.
“Late night eating and skipping breakfast is such an erratic eating pattern which is becoming more prevalent day by day.”Prof. Peter Weissberg, medical director of the British Heart Foundation, said: “This research suggests that eating a meal late at night may contribute to the failure of their blood pressure to reduce.
“It is normal for blood pressure to reduce overnight, even in people with high blood pressure.“However, in some their blood pressure remains elevated throughout the night putting them at potentially higher risk of future complications.”
By Chukwuma Muanya, Assistant Editor at Guardian Newspaper