Many who consider quitting smoking think "the damage is done". Or, "Why bother, it's too late". The scientific data say otherwise. It says the benefits are immediate and long-lasting.
Within the first hour after you stop smoking, blood pressure and pulse decrease and the internal temperature of the hands and feet increase. The compounds produced in the body from smoking constrict blood vessels and raise the heart rate. As they're flushed out of the body, it returns to a normal state.
A few hours later, carbon monoxide levels in the blood return to normal. Cigarette smoke contains Carbon Monoxide (CO), which binds with hemoglobin - the molecule that helps transport oxygen through the blood stream. But that combination reduces the amount of available oxygen. As the CO level decreases, more oxygen is available for its intended purpose: feeding tissues that sustain your life.
After the first 24 hours, the risk of heart attack is already on the downswing. Forty-eight hours after you quit, your nerve endings will change. The stimulation induced by bathing them in nicotine products is radically reduced. You'll begin to recover normal sensation. At the same time, the senses of taste and smell start to recover. Food will taste fresher and you'll be able to detect odors better.
After a couple of weeks, the cravings for nicotine will taper off, only to return (if at all) at random over the next few months. The circulatory system is recovering. The ability to exercise without wheezing and shortness of breath is returning gradually. After a few weeks or months, you'll be able to carry out a normal exercise routine.
Over the next several months, the hack and sinus congestion so common among smokers decreases considerably. Smoke-induced fatigue drops, so the overall energy level increases. The body's systems are regenerating to function at peak level.
As you keep to that long-term commitment, the risk of stroke drops precipitously. For smokers, the risk is twice that of a non-smoker. Within a year it's half what it was. Within 5-15 years it is down to that of someone who has never inhaled a cigarette.
At the same time, similar risks of lung or larynx cancer, as well as bladder, pancreas and others, drop to that of a lifelong non-smoker. Official estimates attribute 87% of lung cancer cases to long-term, heavy smoking. Quitting smoking takes you out of that group within a few years.
Stopping smoking is a permanent commitment to long-term health. The alternative is a greatly increased risk of coronary disease, stroke, a dozen different cancers, COPD and other serious medical problems. Don't let the odds get you. Stop now.