Based on PubMed | Does cigarette smoking increase the risk of endometrial cancer?

Smoking cigarettes does not appear to increase the risk of endometrial (uterine) cancer; in fact, many large studies suggest that current smoking is associated with a lower risk, particularly for postmenopausal endometrial cancer. ^[1] This inverse association is seen in both case‑control and cohort data, but it does not outweigh the many serious harms of smoking to overall health. ^{[2] [3]}

What the evidence shows

• Multiple epidemiologic studies report that women who currently smoke have a lower risk of endometrial cancer than women who never smoked, with risk reductions roughly in the 30–50% range in some analyses. ^{[4] [2]}
• The apparent risk reduction is most consistently observed in postmenopausal endometrial cancers, and the risk among former smokers tends to move back toward that of never‑smokers. ^{[1] [2]}
• In a large U.S. cohort (NIH‑AARP), endometrial cancer risk was lower in current smokers (relative risk about 0.65) and modestly lower in former smokers (about 0.89) compared with never smokers; the reduction was strongest closer to the time of smoking and diminished ≥10 years after quitting. ^[2]
• Earlier case‑control studies also found lower risk among current smokers, including heavy smokers, with some studies noting the pattern primarily in postmenopausal women. ^{[5] [4]}

Possible biological reasons

Researchers think the inverse link may reflect smoking’s anti‑estrogenic effects. ^[6] Cigarette smoking can alter estrogen metabolism and is associated with earlier natural menopause and lower lifetime estrogen exposure, which could reduce stimulation of the uterine lining (endometrium). ^[6] This mechanism aligns with the observation that the effect seems more pronounced after menopause. ^[1]

Important cautions

• Despite this inverse association for endometrial cancer, smoking greatly increases the risk of many other cancers (including lung, head and neck, bladder, pancreas, and cervical), heart disease, stroke, and chronic lung disease. No guideline recommends smoking as a preventive strategy for endometrial cancer. ^[3]
• Former smokers tend to lose most or all of the apparent “protective” association over time, underscoring that smoking is not a lasting risk‑reduction method for the uterus and remains broadly harmful. ^{[1] [2]}

How this fits with overall risk factors

Endometrial cancer risk is primarily driven by factors that increase unopposed estrogen exposure to the uterine lining, such as obesity, older age, certain hormone therapies (estrogen without progesterone), and conditions like polycystic ovary syndrome. ^[7] Managing weight, treating metabolic conditions, and using balanced hormones where appropriate are evidence‑based ways to lower risk. ^[7]

Bottom line

• Current cigarette smoking is associated with a lower risk of endometrial cancer, most notably for postmenopausal disease, but this does not translate into a health benefit because smoking causes many other serious diseases and deaths. ^{[1] [3]}
• Quitting smoking is still one of the best things anyone can do for overall health, and endometrial cancer prevention should focus on modifiable, healthy strategies like weight management and appropriate hormone balance. ^{[3] [7]}

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Key data at a glance

Exposure category	Approximate risk vs. never smokers	Notes
Current smokers	Lower risk (e.g., RR ~0.65 in a large cohort)	Inverse association most evident in postmenopausal disease; effect diminishes after cessation. [2] [1]
Former smokers	Slightly lower to similar risk (e.g., RR ~0.89 overall)	Risk approaches that of never smokers with longer time since quitting (≥10 years showed no reduction). [2] [1]
Never smokers	Reference	Baseline comparison group. [2]

References supporting table entries: NIH‑AARP cohort analysis and national summaries. ^{[2] [1]}