What does smoking do to your biological age?
Smoking measurably accelerates the biological ageing of lung cells, the immune system and the reproductive system. Quitting smoking reverses part of that damage, in some cases even completely after ten years.
Smoking significantly accelerates the ageing of lung cells. In the lung tissue of smokers and COPD patients, damaged proteins accumulate in small cellular vesicles because a normal cellular clean-up system no longer functions properly. Notably, this pattern closely resembles what is seen in naturally ageing lung cells. The amount of these damaged-protein accumulations was associated with the severity of pulmonary emphysema. This holds true for both cell studies and human tissue.
Smoking also has a measurable effect on DNA, through so-called epigenetic changes. These are chemical marks on the DNA that regulate which genes are switched on or off, and they are used as a measure of biological ageing. Smoking exposure was associated with changes at more than a hundred gene loci in immune cells. This is an association, not a proven causal relationship, and the research did not involve tobacco smokers exclusively. However, it fits the broader picture that smoking accelerates the biological clock.
The consequences for the immune system are concretely noticeable. Smokers with the skin condition psoriasis respond demonstrably less well to modern immunotherapy than non-smokers: the likelihood of a good treatment outcome fell by approximately 20% in both current and former smokers. This suggests that smoking alters the immune system for a prolonged period, even after quitting.
The effects on fertility have been studied extensively. Smoking damages both egg and sperm quality, increases the risk of miscarriage and preterm birth, and reduces birth weight by 150 to 300 grams in children carried to full term. Quitting smoking substantially reduces these risks. The same applies to the risk of bacterial pneumonia: the risk rises sharply with the amount smoked, but after ten years of not smoking the risk is equivalent to that of people who have never smoked. Quitting is therefore worthwhile, even if you have smoked for a long time.
The claims about lung cell ageing are based on combinations of mouse and human tissue research (no large RCTs). The epigenetic claim concerns smoking exposure in a broader sense, not exclusively tobacco smoke. The fertility findings come from an older review article. The immune effects in psoriasis are observational.
What does alcohol do to your biological age?
Alcohol accelerates multiple biological ageing processes, including gut damage, inflammation, and brain deterioration. The older you are, the more vulnerable your body is to that damage, so drinking less is worthwhile at every stage of life.
Which lifestyle factors influence your biological age the most?
Sitting for prolonged periods, a disrupted circadian rhythm and muscle loss are the best-supported negative factors for your biological age; exercising regularly and maintaining a consistent sleep-wake rhythm are the most concrete steps you can take right now.
How can I measure my biological age?
Epigenetic clocks, in particular GrimAge and PhenoAge, currently offer the best estimate of your biological age, but they are not yet ready for straightforward home use and require expert interpretation.
How large can the difference between my chronological age and my biological age be?
The typical spread between your biological and calendar age is around one to two years. Studies mention no hard upper limit, but biological age does predict health risks better than your year of birth.
How quickly can you change your biological age with exercise?
Regular moderate to vigorous exercise is associated with a biological age that comes out 1 to 3 years lower, and molecular changes in muscles are measurable after just a few weeks. Whether a lower score on an epigenetic clock truly means living healthier or longer has not yet been proven: treat it as an encouraging signal, not a guarantee.
Does your biological age change differently at night than during the day?
The night is biologically not a pause but an active recovery phase, and that phase deteriorates noticeably with age. Those who protect their sleep rhythm, with fixed times, limited screen use before bedtime and a longer nightly eating break, preserve that recovery function for longer.