What does smoking do to your biological age?
Smoking measurably accelerates the biological ageing of lung cells, the immune system, and the reproductive system. Stopping smoking reverses some of that damage, in some cases even completely after ten years.
Smoking considerably speeds up the ageing of lung cells. In lung tissue from smokers and people with COPD, damaged proteins build up inside small pouches within the cell, because a normal cellular clean-up system no longer works properly. Strikingly, this pattern closely resembles what you see in naturally ageing lung cells. The amount of these damaged-protein accumulations was linked to the severity of lung emphysema. This was found in both studies with cells and in human tissue.
Smoking also has a measurable effect on DNA, through so-called epigenetic changes. These are chemical tags on the DNA that control which genes are switched on or off, and they are used as a measure of biological ageing. Smoke exposure was associated with changes at more than a hundred gene locations in immune cells. This is an association, not a proven cause-and-effect relationship, and the research did not involve tobacco smokers exclusively. But 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 measurably less well to modern immune therapy than non-smokers: the chance of a good treatment outcome fell by around 20% in both current and former smokers. This suggests that smoking changes the immune system for a long time, even after you have stopped.
The effects on fertility have been studied widely. Smoking damages both egg and sperm quality, increases the risk of miscarriage and premature birth, and reduces birth weight by 150 to 300 grams in babies carried to full term. Stopping smoking reduces these risks considerably. The same applies to the risk of bacterial pneumonia: the risk rises sharply with how much you smoke, but after ten years of not smoking the risk is equal to that of people who have never smoked. Stopping is worthwhile, then, 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 studies in people with a control group). The epigenetic claim concerns smoke exposure in a broader sense, not tobacco smoke exclusively. The fertility findings come from an older review article. The immune effects in psoriasis are from people followed over time without a control group.
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?
DNA clocks, and GrimAge in particular, give the most reliable picture of your biological age. These measurement methods are currently used mainly in research.
Can you really lower your biological age, and does research support this?
There are promising hints that biological age is measurable and perhaps steerable, but this has not been proven. Wait for larger studies in people before basing major decisions on this.
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.