Entering a smoking history that changed

Why does a changing history need periods?

People who smoke often vary their smoking habits over the years, which can make pack years difficult to work out. FAQ 5 notes that changing smoking patterns over a lifetime can complicate what seems a simple calculation.

In the calculator, each type of tobacco has its own step, and each step can hold as many periods as you need. A period is an amount and a number of years. Choose Add another period whenever the amount changed.

How do I enter cutting down or smoking more?

Add one period for each amount. The calculator’s own example is 10 cigarettes a day for 5 years, then 20 a day for 20 years: two periods under Cigarettes. That comes to 10 × 5 + 20 × 20 = 450, and 450 ÷ 20 = 22.5, which the calculator shows as 23 pack years, with 22.5 before rounding.

What about years when I did not smoke?

Leave them out: enter only the periods when you smoked. The calculator does not ask for the dates of each period, and the order you enter them in makes no difference to the total.

The optional history step asks how many years you smoked in total, and says: “Leave out any years when you had stopped completely.”

What if I stopped and started again?

Enter each spell of smoking as its own period. On the history step you can also say whether you smoke now and, if you have stopped, when you stopped (the month is optional).

FAQ 2 explains why these details matter: starting and stopping dates show the time of exposure, as some smoking-related diseases appear to be age dependent and decline on stopping smoking. It recommends recording starting and stopping dates, years smoked and pack years.

What if I smoked more than one type?

On “What have you smoked?”, tick everything you have smoked regularly at any time in your life. Each type gets its own step and its own periods, and the periods can overlap: if you smoked cigarettes and a pipe in the same years, enter both. Roll-ups go under Loose tobacco, by weight a week (see roll-ups and loose tobacco).

Years spent only vaping are not counted: the calculator records combustible smoking products only. FAQ 11 says: “Years vaped may be the best way to record vaping on the clinical record.”

How can I remember what I smoked?

FAQ 8 says the calculation relies on an accurate history, which can be found by recalling what was smoked in each decade of life. One way to do that:

1. Go through your life a decade at a time: teens, twenties, thirties and so on.
2. For each decade, note what you smoked, roughly how much a day (or a week, for loose tobacco and waterpipe), and for how many years.
3. Note any years when you stopped completely.
4. Enter one period for each steady amount of each type.

What does a changing history add up to?

This person would enter 32 as the total years smoked (5 + 20 + 7), leaving out the 3 years when they had stopped.

How do I keep it up to date?

FAQ 8 says that people who continue to smoke should have their pack years recalculated every five years. “Save or share a link” keeps your answers in the link itself: open it later and choose Change answers to add a period. You can also download or email a PDF, or print the result.

If you are worried about your health, speak to your GP practice or use NHS 111. For the full method, see how the calculation works.