Docs: Impact of concurrent and consecutive tobacco smoking on LLP and PLCO risk inputs

docs/cigarette-equivalents--quantity.csv

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+Cigarettes,Rolling tobacco,Small cigar,Medium cigar,Large cigar,Pipe,Cigarillo,Heated tobacco
+1,2,1.5,2,4,2.5,2,1
+2,1,1.3,1,0.5,0.8,1,2
+3,1.5,2,1.5,0.75,1.2,1.5,3
+4,2,2.7,2,1,1.6,2,4
+5,2.5,3.3,2.5,1.25,2,2.5,5
+6,3,4,3,1.5,2.4,3,6
+7,3.5,4.7,3.5,1.75,2.8,3.5,7
+8,4,5.3,4,2,3.2,4,8
+9,4.5,6,4.5,2.25,3.6,4.5,9
+10,5,6.7,5,2.5,4,5,10
+11,5.5,7.3,5.5,2.75,4.4,5.5,11
+12,6,8,6,3,4.8,6,12
+13,6.5,8.7,6.5,3.25,5.2,6.5,13
+14,7,9.3,7,3.5,5.6,7,14
+15,7.5,10,7.5,3.75,6,7.5,15
+16,8,10.7,8,4,6.4,8,16
+17,8.5,11.3,8.5,4.25,6.8,8.5,17
+18,9,12,9,4.5,7.2,9,18
+19,9.5,12.7,9.5,4.75,7.6,9.5,19
+20,10,13.3,10,5,8,10,20
+21,10.5,14,10.5,5.25,8.4,10.5,21
+22,11,14.7,11,5.5,8.8,11,22
+23,11.5,15.3,11.5,5.75,9.2,11.5,23
+24,12,16,12,6,9.6,12,24
+25,12.5,16.7,12.5,6.25,10,12.5,25
+26,13,17.3,13,6.5,10.4,13,26
+27,13.5,18,13.5,6.75,10.8,13.5,27
+28,14,18.7,14,7,11.2,14,28
+29,14.5,19.3,14.5,7.25,11.6,14.5,29
+30,15,20,15,7.5,12,15,30

docs/cigarette-equivalents--time.csv

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+Time (mins),Shisha,Chewing tobacco,Dry snuff
+Cigarettes / min:,1.25,0.133,0.133
+10,12.5,1.33,1.33
+15,18.75,1.995,1.995
+20,25,2.66,2.66
+25,31.25,3.325,3.325
+30,37.5,3.99,3.99
+35,43.75,4.655,4.655
+40,50,5.32,5.32
+45,56.25,5.985,5.985
+50,62.5,6.65,6.65
+55,68.75,7.315,7.315
+60,75,7.98,7.98
+65,81.25,8.645,8.645
+70,87.5,9.31,9.31
+75,93.75,9.975,9.975
+80,100,10.64,10.64
+85,106.25,11.305,11.305
+90,112.5,11.97,11.97
+95,118.75,12.635,12.635
+100,125,13.3,13.3
+105,131.25,13.965,13.965
+110,137.5,14.63,14.63
+115,143.75,15.295,15.295
+120,150,15.96,15.96
+125,156.25,16.625,16.625
+130,162.5,17.29,17.29
+135,168.75,17.955,17.955
+140,175,18.62,18.62
+145,181.25,19.285,19.285
+150,187.5,19.95,19.95
+155,193.75,20.615,20.615
+160,200,21.28,21.28
+165,206.25,21.945,21.945
+170,212.5,22.61,22.61
+175,218.75,23.275,23.275
+180,225,23.94,23.94

docs/cigarette-equivalents.md

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+# Cigarette equivalents
+
+This note summarises the cigarette-equivalent conversion data in:
+
+- `docs/cigarette-equivalents--quantity.csv`
+- `docs/cigarette-equivalents--time.csv`
+
+It is a modelling reference for converting different tobacco products into cigarette-equivalent amounts. It is not clinical guidance.
+
+## Quantity-based products
+
+The quantity CSV uses the `Cigarettes` column as the target cigarette-equivalent amount. The other columns show how much of each product is equivalent to that number of cigarettes.
+
+For example, the `20` cigarette row gives:
+
+| Product | Equivalent quantity for 20 cigarettes |
+| --- | ---: |
+| Cigarettes | 20 cigarettes |
+| Rolling tobacco | 10 roll-ups |
+| Small cigar | 13.3 small cigars |
+| Medium cigar | 10 medium cigars |
+| Large cigar | 5 large cigars |
+| Pipe | 8 full pipe loads |
+| Cigarillo | 10 cigarillos |
+| Heated tobacco | 20 heated tobacco sticks |
+
+These values imply the following cigarette-equivalent factors:
+
+| Product | Input unit | Cigarette-equivalents per unit |
+| --- | --- | ---: |
+| Cigarettes | 1 cigarette | 1 |
+| Rolling tobacco | 1 roll-up | 2 |
+| Small cigar | 1 small cigar | 1.5 |
+| Medium cigar | 1 medium cigar | 2 |
+| Large cigar | 1 large cigar | 4 |
+| Pipe | 1 full pipe load | 2.5 |
+| Cigarillo | 1 cigarillo | 2 |
+| Heated tobacco | 1 heated tobacco stick | 1 |
+
+Use this formula for quantity-based products:
+
+```text
+cigarette-equivalents = product quantity x cigarette-equivalents per unit
+```
+
+If the product is not smoked daily, first calculate the cigarette-equivalent amount for each smoking occasion, then normalise it to an average daily amount if the risk model needs cigarettes per day.
+
+For example:
+
+```text
+1 large cigar per week = 1 x 4 cigarette-equivalents per week
+                       = 4 / 7
+                       = 0.57 cigarette-equivalents per day
+```
+
+## Rolling tobacco and grams
+
+The prototype asks about rolling tobacco in grams, but the quantity CSV maps rolling tobacco as roll-ups. Use this assumption to convert between them:
+
+```text
+1 roll-up = 0.5g rolling tobacco
+```
+
+The quantity CSV implies:
+
+```text
+1 roll-up = 2 cigarette-equivalents
+```
+
+So rolling tobacco can be converted directly from grams:
+
+```text
+roll-ups = grams of rolling tobacco / 0.5
+
+cigarette-equivalents = roll-ups x 2
+                      = (grams of rolling tobacco / 0.5) x 2
+                      = grams of rolling tobacco x 4
+```
+
+Examples:
+
+| Rolling tobacco | Roll-ups | Cigarette-equivalents |
+| ---: | ---: | ---: |
+| 0.5g | 1 | 2 |
+| 2.5g | 5 | 10 |
+| 5g | 10 | 20 |
+| 7.5g | 15 | 30 |
+
+The reverse calculation is:
+
+```text
+grams of rolling tobacco = cigarette-equivalents / 4
+```
+
+For example:
+
+```text
+20 cigarette-equivalents = 20 / 4
+                         = 5g rolling tobacco
+```
+
+## Time-based products
+
+The time CSV gives cigarette-equivalents by minutes of use. Its second row defines the cigarette-equivalents per minute:
+
+| Product | Cigarette-equivalents per minute |
+| --- | ---: |
+| Shisha | 1.25 |
+| Chewing tobacco | 0.133 |
+| Dry snuff | 0.133 |
+
+Use this formula for time-based products:
+
+```text
+cigarette-equivalents = minutes of use x cigarette-equivalents per minute
+```
+
+Selected examples from the CSV:
+
+| Time | Shisha | Chewing tobacco | Dry snuff |
+| ---: | ---: | ---: | ---: |
+| 10 minutes | 12.5 | 1.33 | 1.33 |
+| 30 minutes | 37.5 | 3.99 | 3.99 |
+| 60 minutes | 75 | 7.98 | 7.98 |
+| 120 minutes | 150 | 15.96 | 15.96 |
+| 180 minutes | 225 | 23.94 | 23.94 |
+
+The CSV stores chewing tobacco and dry snuff values to 3 decimal places before display in the minute rows.
+
+## Applying the conversions
+
+To calculate a total cigarette-equivalent amount for a smoking period:
+
+1. Convert each selected tobacco product into cigarette-equivalents.
+2. Normalise each product to the same time period, usually an average per day.
+3. Add product amounts only where they are smoked during the same calendar period.
+4. Keep smoking duration as calendar years with tobacco use, not the sum of per-product durations.
+
+For example, someone who smokes 10 cigarettes per day and 2.5g rolling tobacco per day has:
+
+```text
+cigarettes = 10 cigarette-equivalents per day
+
+rolling tobacco = 2.5g x 4
+                = 10 cigarette-equivalents per day
+
+total = 10 + 10
+      = 20 cigarette-equivalents per day
+```
+
+If those products were smoked concurrently, the daily cigarette-equivalent amounts should be added for the overlapping years. If they were smoked consecutively, calculate separate periods before deriving any average intensity.
+
+## Data notes
+
+- The v4.1, v4.2 and v4.3 prototype tobacco type lists do not currently include heated tobacco, chewing tobacco or dry snuff.
+- Heated tobacco appears in the quantity CSV only. Chewing tobacco and dry snuff appear in the time CSV only.
+- The prototype's rolling tobacco question uses gram bands, such as `Less than 10g` and `10g to 30g`. A calculator needs a representative gram value, or a more precise input, before it can calculate an exact cigarette-equivalent amount from those bands.
+- The prototype's shisha question uses time bands, such as `Up to 30 minutes` and `30 minutes to 1 hour`. A calculator needs a representative minute value, or a more precise input, before it can calculate an exact cigarette-equivalent amount from those bands.
+- The `1` cigarette row in `docs/cigarette-equivalents--quantity.csv` lists rolling tobacco as `2`. That does not match the rest of the rolling tobacco column, where the equivalent roll-up quantity is `cigarettes / 2`. With `1 roll-up = 0.5g` and `1 roll-up = 2 cigarette-equivalents`, the expected equivalent for `1` cigarette would be `0.5` roll-ups, or `0.25g` rolling tobacco.