Even One Cigarette is Two Too Many

“Doc, I’m down to one cigarette a day”. That’s great, but you have to stop altogether. “I don’t want to gain weight if I quit. What do you think about e-cigarettes?”

Over the past several years, the number of people who smoke has dropped to an all time low. About 13% of US adults smoke, but that still represents about 37 million active smokers. The risks of smoking are well known. Heart attack, stroke, lung disease and cancer all increase with more smoking: the greater the number of cigarettes smoked and the longer a person smokes, the higher the risk for problems. Many people believe that cutting from smoking 20 to 25 cigarettes per day to only one or two per day will cut their risk. The idea is that a cigarette a day can’t be harmful. What is the data?  Researchers examined 5.6 million people and found that cutting the number of cigarettes from 20 per day to one per day reduced the risk for cancer, but the risk for heart disease persisted.  Compared to a nonsmoker, smoking 20 cigarettes per day increased the risk for heart disease in men by 100% (doubling the risk) and by 184% in women. Compared to those who never smoked, smoking only one cigarette per day increased the risk for heart disease by 50% in both men and women.  In addition, there is an excess risk for stroke with only one cigarette a day. The conclusion was that even one cigarette per day puts a person at significant risk for a heart attack or stroke. The goal must be zero cigarettes.

One of the barriers to quitting is that smokers don’t want to gain weight when they stop smoking. Given the fact that both smoking and obesity put people at risk for heart disease, which is worse, smoking or weight gain? Weight gain in quitters is the result of an increased appetite and lower energy levels.  The amount of weight gained after quitting is usually less than 10 pounds, but can be as high as 30 pounds. Weight goes up for about 5 years after smoking cessation and then slowly comes down.  In a recent study, it was found that stopping smoking reduced the risk for cardiac deaths regardless of weight gain.  This reduction occurred in those who gained weight and those who didn’t gain weight; the weight gain didn’t offset the benefits of smoking cessation on the death rate. The patients who gained weight also had more diabetes than those who didn’t gain weight. Even with weight gain and diabetes, there were less cardiac deaths. This data shows that smoking is worse than weight gain. 

What is the best way to stop smoking?  The main determinant is the smoker’s desire to quit. If you don’t really want to stop, then quitting will be nearly impossible. Some people can stop cold turkey. Most, however, need help in some form. Smoking cessation aids (such as nicotine patch, Chantix and Wellbutrin) can help people quit.  How safe are they? The cardiovascular safety of these aids has been tested in the general population of smokers and they do not increase the risk for heart attack and stroke.  The safety in patients with heart disease is not yet known. How effective are they? In a recent large trial only 3% of people using these aids were smoke free at six months. An emerging method of quitting is the use of the electronic cigarette (e-cigarette) or “vaping”.  The e-cigarette is a battery-powered device that heats liquid nicotine and flavorings (such as vanilla or cinnamon) into a vapor cloud that is inhaled. The data on e-cigarettes are still evolving, but preliminary studies show that they are less harmful than traditional cigarettes. Less harmful does not mean safe, however the degree of harm has not yet been defined. By altering the amount of nicotine in the device, smokers can titrate the nicotine down and quit slowly. However, a recent study showed that smoking cessation with e-cigarettes was not any better than other smoking cessation aids. The other major concern with e-cigarettes is their use in the adolescent population. Vaping has exploded amongst teens. Many studies have shown that e-cigarette use in young people doubles the odds of smoking traditional cigarettes. The FDA is now cracking down on e-cigarette manufacturers, trying to stop their advertising and sale of these products to teens.

In summary, the number one priority for any smoker is to stop smoking, using any means (going cold turkey or using smoking cessation aids or e-cigarettes) and then work to lose the weight that is gained. 

My Apple Watch says that I am in Afib!

Apple just came out with a new watch. In addition to telling time and reading text messages and email, the new watch has electrocardiogram (EKG) capabilities. When the EKG detects an irregular heart beat (atrial fibrillation, Afib) it alerts the wearer. How well will this new technology perform in the real world?

Using Bayes calculation and assuming (a big assumption) that the Apple watch can detect Afib with a sensitivity of 99% and a specificity of 99%, we need to determine the prevalence of Afib in the population. This is not easy and there is scant data. Using Dr John Mandrola’s recent article in JAMAnetwork (“Screening for Atrial Fibrillation Comes with Many Snags”, August 2018), we can get a starting number. A study screening 75 to 76 year old Swedes found new Afib in 0.5% of the screened population.

If we put these numbers into Bayes formula, a pretest probability of 0.5% yields a post-test probability of 33%. In other words, if the chance a person has Afib is 1 in 200 and the watch detects Afib, the posttest probability of Afib is 1 in 3. This is a substantial increase and may be worth additional testing and perhaps treatment.

But…

We don’t know the true sensitivity and specificity. A sensitivity and specificity of 99% is almost never achieved by a diagnostic test, even the best tests come in at 90% to 95%. Testing the sensitivity and specificity of the Apple watch’s ability to detect Afib can be done and it won’t be a difficult undertaking. For example, Apple watches can be given to patients with pacemakers who go in and out of Afib. The watch can then be compared to the pacemaker interrogation to see if it accurately detects Afib and then the sensitivity and specificity can be calculated.  This study would not require too many patients, can be done in a short time and would not be that costly.

The true prevalence of Afib, however, is another story.  This will require a much larger and more extensive study. It would require many thousands of people, monitored for long periods of time (likely years) and would be very costly. In addition, the prevalence noted above is for older patients. The prevalence will be lower in younger unselected patients. If we cut the prevalence in half, to 0.25% or 1 in 400 people, then the posttest probability becomes 20%, still a substantial increase, but less impressive and more likely the watch will have produced a false positive. If the true prevalence is even lower, say by an order of 10 (1 in 2000 people or 0.05%), then the posttest probability is only 5%. It would be much more likely that the result would be a false positive.

The bottom line is that we don't know how accurate the Apple watch will be in detecting Afib. However, even if it's detection rate is nearly perfect, it ability to find Afib is dependent on the prevalence of Afib in the community. If there is a higher prevalence (as would be the case in older patients or heart patients who are hospitalized) then the chance of finding Afib is higher. If the prevalence is low, an irregular heart beat on the watch is more likely a false positive and not Afib. So, if your Apple watch says that you are in Afib, try to keep this in perspective.