TCGA TOBACCO_SMOKING_HISTORY含义

在UCSC Xena下载的临床信息中有tobacco_smoking_history这列信息，从1到5，知道是跟吸烟有关但不知道什么数字含义，google查到可能的解释

• Lifelong Non-smoker (less than 100 cigarettes smoked in Lifetime) = 1
• Current smoker (includes daily smokers and non-daily smokers or occasional smokers) = 2
• Current reformed smoker for > 15 years (greater than 15 years) = 3
• Current reformed smoker for ≤15 years (less than or equal to 15 years) = 4
• Current reformed smoker, duration not specified = 5
• Smoking History not documented = 7

另有图为证

https://groups.google.com/forum/#!topic/cbioportal/irEXZRj9Who