Breaking news: smoking is bad for you

Okay, we all know this. Still, it’s important to have the occasional reminder of just how detrimental smoking can be for one’s health. Two news studies have come out about the effect of smoking on one's longevity, and the news is not good. Would you believe that smoking may cost you over a decade of your life?

Kristin Pirie and her colleagues from the University of Oxford have compiled an enormous study that included over a million women, all born around 1940. The women were categorized based on whether they had ever smoked, or if still smoking, how many cigarettes per day they smoked. If they had permanently quit smoking before the age of 55, they were grouped by age at which they had quit. The women were resurveyed three and eight years later and at the end of the study (an average of twelve years after recruitment) to see how their health and/or smoking habits had changed. 

On average, smoking tripled a woman’s chances of dying during the study period. The risk increased with the number of cigarettes smoked per day. Smoking fewer than ten cigarettes per day doubled the mortality risk compared with women who had never smoked. Overall, the authors estimate that continuing to smoke can take an average of eleven years off a woman’s life.

A study in Japan, conducted by Sarah Darby and her colleagues at the Radiation Effects Research Foundation and including over 60,000 men and women, yielded similar results. Men who continued to smoke lost about eight years of their lives, and women lost about ten.

The news wasn’t all bad though. Quitting improves a person's odds substantially. Pirie found that women who had smoked their last cigarette before the age of 30 avoided 97% of the harm. Quitting at age 50 resulted in about a two-thirds reduction in mortality risk. Darby's study also found that much of the harm was avoided by quitting smoking, and the sooner the better. 

Pirie, K., Peto, R., Reeves, G., Green, J., & Beral, V. (2012). The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK The Lancet DOI: 10.1016/S0140-6736(12)61720-6

Sakata, R., McGale, P., Grant, E., Ozasa, K., Peto, R., & Darby, S. (2012). Impact of smoking on mortality and life expectancy in Japanese smokers: a prospective cohort study BMJ, 345 (oct25 2) DOI: 10.1136/bmj.e7093