Smoking speeds up ageing process

A recent Mendelian randomization (MR) study provides genetic evidence showing that smoking can accelerate ageing as a result of shortened leucocyte telomere length (LTL). However, quitting may help reduce such risk.

“Our study shows that smoking status and cigarette quantity can result in the shortening of LTL, which is an indicator of tissue self-repair, regeneration, and ageing,” said Dr Siyu Dai, assistant professor in the School of Clinical Medicine, Hangzhou Normal University, China, in her presentation at the ERS International Congress 2023 held in Milan, Italy. [https://www.eurekalert.org/news-releases/1000842]

“In other words, smoking can accelerate the process of ageing, while quitting may considerably decrease the related risk,” she added.

Dr Dai and her colleague Dr Feng Chen from The Chinese University of Hong Kong analysed data from the UK Biobank, which included genetic summary statistics of smoking status (ie, current smoker, never smoker, and previous smoker).

They used a two-sample MR method, which utilizes the variations in genes (single nucleotide polymorphisms or SNPs) inherited from parents, to understand how exposure to a modifiable environmental factor (eg, smoking) causes a disease or health condition (eg, shorter LTL).

A total of 472,174 eligible participants of European descent were assessed. Moreover, 113 instrumental SNPs related to smoking status (current: 15 SNPs; never: 78 SNPs; previous: 20 SNPs) and 11 SNPs related to pack years of cigarette smoking were included in the analysis. [ERS 2023, abstract OA4230]

Current smoking status showed a statistically significant relation to shorter LTL (r, ‒0.27; p=0.013), while never smoking positively correlated with LTL (r, 0.21; p<0.0001). On the other hand, former cigarette smoking also showed a negative, but this did not reach statistical significance (r, ‒0.15; p=0.221).

“We found that current smoking status was statistically significantly associated with shorter LTL, whereas previous smokers and people who had never smoked didn’t show significantly shorter LTL,” Dr Dai said. “Among people who used to smoke, there was a trend towards shorter telomere length, but this was not statistically significant.”

Faster ageing

Notably, individuals with greater cigarette consumption or larger pack years were significantly more likely to have shorter LTL (r, ‒0.08; p=0.008).

“People who smoked the greater number of cigarettes had significantly shorter LTL,” said Dr Dai. “In summary, smoking may cause the shortening of LTL, and the more cigarettes smoked, the stronger the shortening effect.”

Telomeres are like a thread of repetitive DNA sequences responsible for protecting the ends of chromosomes. They become shorter every time a cell divides. Eventually, telomeres become very short that the cell can no longer divide successfully, leading to its death. This is part of the ageing process. [https://www.eurekalert.org/news-releases/1000842]

“Our study adds to the evidence that smoking causes ageing,” Dr Dai said. “As there are clear health benefits of smoking cessation, it is time to include cessation support as well as treatment into daily clinical management to help us to create a smoke-free environment for the next generation.”

Dr Dai and Dr Chen plan to conduct further research to validate their findings.