This article originally appeared on Tonic.
No matter how you try to slice it, inhaling any amount of cigarette smoke is bad for your health. A large, new meta-analysis published in The BMJ found that smoking just one cigarette a day could drastically increase the risk of coronary heart disease and stroke.
Smoking socially, occasionally, or otherwise inconsistently is generally seen as “safer,” especially compared to people who smoke a pack a day or more. But there is no such thing as safe smoking whatsoever, this study concludes.
The systematic review was extensive, examining 141 prospective cohort studies published in 21 countries between 1946 and 2015. It followed a total of 5.6 million people to see who developed coronary heart disease and 7.3 million people for stroke. The authors only looked at generally healthy individuals, excluding patients taking medication for cardiac related disorders, for example.
They found that men who have about one cigarette per day had a 48 percent higher risk of heart disease and 25 percent higher risk of stroke compared to people who have never smoked. For women, the news is even grimmer, with a 57 percent and 31 percent higher risk for heart disease and stroke, respectively, compared to never smokers.
When controlling for confounding factors, such as age, the risk is even higher—for men, there’s a 74 percent and 30 percent higher risk for heart disease and stroke respectively. For women it’s 119 percent and 46 percent.
Light smoking is worse than many health professionals or smokers realize. The study authors, which included Professor Allan Hackshaw of the Cancer Research UK and UCL Cancer Trials Centre at University College London, estimated the relative risks of smoking one, five, or twenty cigarettes (an entire pack) a day.
They expected the health risk of one cigarette to be five percent of the risk of smoking 20 (one divided by 20; this is true for lung cancer risk). But they found that men who lit up just one cigarette a day had 46 percent of the increased heart disease risk and 41 percent of the excess stroke risk associated with smoking a pack a day. For women, smoking one cigarette a day accounted for 31 percent of the heart disease risk and 34 percent of the stroke risk of smoking 20 cigs.
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The researchers also controlled for people whose smoking habits might have changed over time since participating in a smoking study might encourage you to smoke less. But when only examining studies with follow-up to 1995, they found their results didn’t change.
Using meta-regression, the researchers also controlled for cholesterol levels, blood pressure, body mass index, education, diabetes history, and even level of exercise. Yet again, their results were undeviating.
These findings are consistent with a January 2017 JAMA study that looked at approximately 290,000 adults and found “low-intensity smoking over the lifetime was associated with a significantly higher risk of all-cause mortality, including deaths from lung cancer and cardiovascular disease [compared to never smokers].”
But this was the first study to combine results relating to both stroke and coronary heart disease, providing incentive for smokers to quit entirely instead of just cutting down. (The biggest death risk from smoking isn’t lung cancer, it’s heart disease.)
In the US, approximately 370,000 people die each year from coronary heart disease and 140,000 die from stroke. Between 15 and 33 percent of cardiovascular disease deaths have been attributed to smoking.
“Although cutting down has clear benefits, particularly for risk of cancer, the reduction in cardiovascular disease risk is not as large as smokers might expect,” the authors wrote. They concluded: “We show clearly that no safe level of smoking exists for cardiovascular disease… Smokers need to quit completely rather than cut down if they wish to avoid most of the risk associated with heart disease and stroke, two common and major disorders caused by smoking.”
So what about e-cigarettes? Turns out, because of increased exposure to ultrafine particles and other toxins, those who vape may still be at increased risk for heart disease and stroke, although e-cigs do release lower levels of carcinogens. The study authors say e-cigarettes “are an important component of harm reduction that can help people to quit completely.”
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