That's a good question, Uma.
I've been looking into lung cancer facts. Recently there have been reports that lung cancer is on the rise (in spite of smoking being way down) for women. The reason given is that women started smoking in larger numbers decades after men, so women are catching up. But my research so far hasn't supported that. The vast majority of lung cancer in smokers happens in the elderly (About 2 out of 3 people diagnosed with lung cancer are 65 or older; fewer than 2% of all cases are found in people younger than 45. The average age at the time of diagnosis is about 70), after decades of smoking. Female smoking prevalence peaked in the mid 60's, so it would SEEM to explain why those women are getting lung cancer today. The American Cancer Society estimates for 2013 about 228,190 new cases of lung cancer (118,080 in men and 110,110 in women). That is a very small difference between men and woman, considering the smoking rate difference.
Female smoking never got much above 33.7% (peak in 1966, depending on the source. I used
NHI surveys) and that same year male smoking prevalence was 51.9%. A 20 year old smoker in 1966 would be 67 today. In 1955, male smoking was estimated at 52.6% and female smoking was 24.5%. Those folks who were 20 then would be 77 today. After 1966, female smoking rates dropped to 30.5% in 1970 and 28.9% in 1975. (Male smoking in 1970 was 42.3% and in 1975 39.3%). Even if you just look at those only in their early 20's (21-24), female smoking in that age group peaked in 1966 at 49.2% and dropped to 32.3% by 1970. Male rates in that age group were 61.9% in 1966 and 49.8% in 1970.
If female smoking rates had become close to or matched male smoking rates back in the 50's, 60's and 70's, it would make
sense that lung cancer rates would rise to match. But as you can see, the female smoking rates never got anywhere close to male smoking rates.
So, if smoking is the cause, why are the female lung cancer numbers so close to male numbers today (and on the rise), when there were so fewer female smokers than males? Could it be because so many more females are working and living in urban areas and doing more previously male-dominated jobs now?