Cigarettes are a co-morbidity for almost everything and a risk factor for the rest, but it isn't just first-order disease that may be in the future of cigarette smokers.

A cohort of 1,000 healthy volunteers aged 20 to 70 in 2011 were examined to see why human immune systems vary significantly in terms of how effectively they respond to microbial attacks. Age, sex and genetics are known to have a significant impact on the immune system, the aim of this new study was to identify which other factors had the most influence.

The scientists exposed blood samples taken from individuals in the Milieu Intérieur cohort to a wide variety of microbes (viruses, bacteria, etc.) and observed their immune response by measuring levels of secreted cytokines. Using the large quantities of data gathered for individuals in the cohort, the team then determined which of the 136 investigated variables (body mass index, smoking, number of hours' sleep, exercise, childhood illnesses, vaccinations, living environment, etc.) had the most influence on the immune responses studied. Three variables stood out: smoking, latent cytomegalovirus infection - a virus in the herpes family that is often asymptomatic though dangerous to fetuses - and body mass index.

 Image: New York Film Academy

Analysis of the data showed that the inflammatory response, which is immediately triggered by infection with a pathogen, was heightened in smokers, and moreover, the activity of certain cells involved in immune memory was impaired. In other words, this study shows that smoking disrupts not only innate immune mechanisms, but also some adaptive immune mechanisms. 

Basically, the immune system appears to have something resembling a long-term memory of the effects of smoking. But how? That's where things are unclear and the authors fall back on the modern biological version of the 19th century's "aether" - epigenetics. They use a circumstantial chain 

It's not a plausible biological mechanism, so that will have to wait for another time, but regardless of why it happens, it happens, so stop smoking.