Smoking Does Not Affect This Key Indicator of Aging, Surprising Medical World

Smoking cigarettes is terrible for our health in a myriad of ways, but scientists believe it might not affect a part of our chromosomes linked to aging as previously thought.

An international team of scientists looked at how smoking affects telomeres: compounds at the end of our chromosomes that protect our DNA. They are regarded as the clock of life: We age as they waste away.

Since human telomeres shorten with age, it is widely believed that smoking speeds up aging by speeding up this process.

For the new study published in the journal Open Science, the researchers studied 18 existing datasets featuring information on 12,579 adults collected from 10 countries across four continents. The participants included 4,678 current smokers and 7,901 non-smokers. Blood samples were taken from the participants at the start of each study, and then once again an average of 8.6 years later. This enabled researchers to look at whether the length of their telomeres changed over time.

The information confirmed the results of previous studies indicating smokers have shorter telomeres. However, the scientists didn't find that the telomeres of smokers get shorter faster than non-smokers.

The authors say their work suggests smoking might not explain why the telomeres of smokers are short, and that looking at telomere length might not be as useful for assessing the effects of unhealthy activities like smoking as is currently believed.

Instead, telomeres might not change all that much during adult life, and might not be shaped by behaviors such as eating healthy or unhealthy foods, the scientists think.

Scientists aren't sure why this portion of the smokers' chromosomes might be stubbier. One possible explanation is that smokers have another variable in common, for instance having shorter telomeres in the first place. This might be due to suffering or emotional abuse as a child.

Lead author Professor Melissa Bateson of Newcastle University's Faculty of Medical Sciences commented: "The importance of this study is that it forces us to rethink the value of telomere length as a read-out of how our current lifestyles are affecting our bodies.

"We don't dispute the abundant evidence that smoking is bad for you, but merely the evidence that telomere length is a good way of assessing the biological damage done by smoking and possibly, by extension, other unhealthy behaviors."

Smoking harms nearly every organ in the body, warns the Center for Disease Control and Prevention, and is one of the main causes of preventable deaths, linked to conditions including heart disease and cancer.

Bateson argued: "More generally, the findings underline the need for caution when interpreting correlational data. Just because two variables are correlated does not mean that one variable causes the other."

This research could open up debate around papers such as one published last year where scientists investigated how different types of exercise affect telomeres.

The study, published in the European Heart Journal, suggested high-intensity interval training and endurance training lengthened telomeres and boosted telomerase activity. However, resistance training did not have the same effect.