Air pollution increases the chances of heart attack survivors dying early, research has shown.

Higher levels of tiny sooty particles in the air led to more deaths among patients after they had left hospital.

Experts monitored more than 154,000 patients treated for heart attacks and angina for an average period of 3.7 years.

Exposure to man-made pollutants increased death rates among survivors of acute coronary syndrome (ACS) by 12%, the scientists found.

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This meant that over the study period there were almost 5,000 extra deaths.

The research focused on tiny particles called PM2.5s that measure no more than 2.5 micrometres across - 30 times smaller than the width of a human hair.

Road vehicles, factories and power stations are the main man-made sources of the particles, which lodge deep in the lungs.

The results are published today in the European Heart Journal.

Author Dr Cathryn Tonne, from the London School of Hygiene and Tropical Medicine, said: "We found that for every 10 microgram per cubic metre increase in PM2.5 there was a 20% increase in the death rate.

"For example, over one year of follow-up after patients had been admitted to hospital with ACS, there would be 20% more deaths among patients exposed to PM2.5 levels of 20 micrograms per cubic metre compared to patients exposed to PM2.5 levels of 10 micrograms per cubic metre."

The research, conducted in England and Wales, found that London had the highest estimated concentration of the particles - an average of 14.1 micrograms per cubic metre of air. People living in the North East of England had the lowest exposures.

Previous studies have linked exposure to pollution particles and an increased risk of heart disease and early death. But evidence of the impact of air pollution on survival after heart attacks has been inconsistent.

Patients from poorer backgrounds often live in areas with higher air pollution and tend to do less well after a diagnosis of heart problems.

"This raises the possibility that exposure to air pollution may explain, in part, the differences in prognosis among heart attack patients from different backgrounds," said Dr Tonne.

She added: "Our findings confirm an association between PM2.5 and increased rates of death in survivors of ACS."

The research indicated that other factors also played an important role in reducing the life expectancy of patients in deprived areas.

Also on HuffPost:

Healthy Foods For Your Heart From Shape.com
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  • Avocado

    "Instead of using a whopping dollop of mayonnaise on your sandwich, try using thin slices of avocado," suggests Megan Madden, a registered dietitian in New York, NY. A 1996 study done by researchers in Mexico found that people who ate avocado every day for one week experienced an average 17 percent drop in total blood cholesterol. What's more, their levels of LDL ("bad") cholesterol decreased and HDL ("good") cholesterol increased.

  • Whole Grains

    The soluble fiber found in whole grains such as whole-wheat bread, brown rice, and oatmeal binds the cholesterol in your meal and drags it out of your body, Madden says. "And, when your body needs to utilize cholesterol in the future, it draws on your blood cholesterol supply, effectively lowering your total blood cholesterol level and your risk for heart disease." And oatmeal isn’t just for breakfast; you can enjoy it any time of day with these easy recipes.

  • Olive Oil

    A 2011 study found that people ages 65 or older who regularly used olive oil (for both cooking and as a dressing) were 41 percent less likely to have a stroke compared to those who never use olive oil in their diet. Use a little olive oil instead of butter or drizzle some over pasta, salad or veggies to take advantage of its high mono- and polyunsaturated fats, Madden says. "And although it’s a healthier option, remember to use these oils sparingly, as all fats still contain the same number of calories."

  • Nuts

    Grabbing a handful of nuts is a heart-healthy way to beat the afternoon itch for a cookie, Madden says. "Almonds are very high in heart-healthy monounsaturated fats, vitamin E and fiber, while walnuts are a great plant-based source of an omega-3 fatty acid called alpha-linolenic acid." According to the American Heart Association, monounsaturated fats can help reduce levels of bad cholesterol in your blood and lower your risk of heart disease and stroke.

  • Foods Fortified By Plant Sterols

    Sterols are compounds that compete with the cholesterol in your food for absorption within your digestive tract, Madden says. "Sterols have been shown to lower both total and LDL cholesterol and can be found in certain brands of fortified orange juice, margarine spreads, and milk." Just be sure to check the label -- make sure the margarine is trans fat-free and that "partially hydrogenated oil" does <em>not</em> appear on the ingredient list.

  • Salmon (Or Other Fatty Fish)

    Fatty fish such as mackerel, herring, tuna and salmon are chock full of omega-3 fatty acids, Madden says. "Eating fish twice a week can reduce your risk of developing heart disease by decreasing inflammation and lowering triglyceride levels, and it may even help boost your HDL levels."

  • Asparagus

    Asparagus is one of the best, natural artery-clearing foods around, says Shane Ellison, an organic chemist and author of "Over-The-Counter Natural Cures". "Asparagus works within the 100,000 miles of veins and arteries to release pressure, thereby allowing the body to accommodate for inflammation that has accumulated over the years." It also helps ward off deadly clots, Ellison says.

  • Pomegranate

    Pomegranate contains phytochemicals that act as antioxidants to protect the lining of the arteries from damage, explains Dr. Gregg Schneider, a nutritionally-oriented dentist and expert on alternative medicine. A 2005 study published in the <em>Proceedings of the National Academy of Sciences</em> found that antioxidant-rich pomegranate juice stimulated the body’s production of nitric oxide, which helps keep blood flowing and arteries open.

  • Broccoli

    Broccoli is rich in vitamin K, which is needed for bone formation and helps to keep calcium from damaging the arteries, Schneider says. Not to mention, broccoli is full of fiber, and studies show a high-fiber diet can also help to lower blood pressure and cholesterol levels.

  • Turmeric

    "The spice turmeric is a powerful anti-inflammatory," Schneider says. "It contains curcumin which lowers inflammation -- a major cause of arteriosclerosis (hardening of the arteries." A 2009 study found that curcumin helps reduce the fatty deposits in arteries by as much as 26 percent.

  • Persimmons

    Forget the old 'an apple a day' adage -- it seems eating a daily persimmon is a better way to keep the doctor away. Research shows the polyphenols found in this fruit (which has twice as much fiber and more antioxidants than an apple) can help decrease levels of LDL cholesterol and triglycerides.

  • Orange Juice

    A 2011 study published online in the <em>American Journal of Clinical Nutrition</em> found that drinking two daily cups of 100-percent orange juice can help reduce diastolic (resting) blood pressure. OJ contains an antioxidant that has been found to help improve blood vessel function.

  • Spirulina

    A daily 4,500-milligram dose of this blue-green algae (usually found in supplement or powder form) can help relax artery walls and normalize blood pressure. It may also help your liver balance your blood fat levels -- decreasing your LDL cholesterol by 10 percent and raising HDL cholesterol by 15 percent, according a recent study.

  • Cinnamon

    Just one teaspoon a day of antioxidant-rich cinnamon can help reduce fats in the bloodstream, helping to prevent plaque build up in the arteries and lower bad cholesterol levels by as much as 26 percent, according to recent research. Sprinkle some on your morning coffee or on these delicious crepes.

  • Cranberries

    Research shows that potassium-rich cranberries can help reduce LDL cholesterol levels and help raise the good HDL levels in your body, and regular consumption of the holiday favorite may help reduce your overall risk of heart disease by as much as 40 percent.

  • Coffee

    According to researchers in the Netherlands, people who drank more than two, but no more than four, cups of coffee a day for 13 years had about a 20 percent lower risk of heart disease than people who drank more or less coffee or no coffee at all. Moderation is the key to coffee's heart-health benefits -- the caffeine is a stimulant which can cause a temporary increase in blood pressure, and in excess, can lead to irregular heart beat.

  • Cheese

    Believe it or not, cheese could help lower your blood pressure! A recent study from Brigham and Women's Hospital and Harvard Medical School found that people who eat three servings a day of low-fat dairy have lower (three points less) systolic blood pressure than those who eat less.

  • Green Tea

    Green tea is rich in catechins, compounds that have been shown to decrease cholesterol absorption in your body. Another bonus? It may help prevent cancer and weight gain, too!

  • Watermelon

    Talk about a perfect snack -- watermelon is not only a diet-friendly food, but it can help protect your heart, too! A Florida State University study found that people given a 4,000-milligram supplement of L-citrulline (an amino acid found in watermelon) lowered their blood pressure in just six weeks. Researchers say the amino acid helps your body produce nitric oxide, which widens blood vessels.

  • Spinach

    The potassium and folate found in spinach can help lower blood pressure, and according to recent research, one serving of nutrient-packed leafy greens (like spinach) a day can help reduce your risk of heart disease by 11 percent.

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