New publications
The risk of disease does not decrease in those who quit smoking
Last reviewed: 01.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Ex-smokers, compared with those who never smoked, have an increased risk of developing two inflammatory bowel diseases - Crohn's disease and ulcerative colitis.
Moreover, the risk of colitis remains elevated even two decades after giving up the bad habit.
Researchers from Boston Children's Hospital and Harvard Medical School (both in the US) collected information on 230,000 nurses whose behavior and health were monitored from 1976 to 1989. During this time, Crohn's disease developed in 144 of 124,000 of those who had never smoked, in 117 of 51,000 former smokers, and in 75 of 53,500 of those who continued to kill themselves with cigarette smoke.
After taking into account other risk factors such as age, weight and taking hormonal drugs, the researchers found that 90% of the female smokers in the study developed Crohn's disease, and 35% more often in those who quit the habit than in those who had never smoked. And the longer the subjects smoked, the higher the likelihood of developing the disease. For example, those who smoked a pack a day for 10-25 years became victims of Crohn's disease 1.7 times more often than those who had never smoked. And for those who smoked the same number of cigarettes for more than 25 years, the risk increased by 2.3 times.
Smoking was also associated with ulcerative colitis, a condition that causes pain, diarrhea and bleeding. During the study, the condition was diagnosed in 190 non-smokers, 167 former smokers and 43 current smokers. A comparison of former smokers with current smokers showed that the former had a 50% higher risk of ulcerative colitis. And female smokers had the same risk as those who had never smoked.
Scientists note that over time, the likelihood of developing diseases in those who quit smoking does not decrease. Thus, within 2-5 years after quitting the harmful habit, ulcerative colitis developed in participants three times more often than in those who continued to use tobacco inhalations. And 20 years after the last puff, the risk of developing this disease was one and a half times higher.