Rational E.T.
You will not able to say “Yeah but I only smoke two cigarettes a day you know.”
There seems to be a plethora of studies showing that light smokers (even smoking less than 4 cigarettes a day) still face significantly higher risk of diseases than non-smokers. The article “Health Effects of Light and Intermittent Smoking” (Circulation, April 6, 2010 vol. 121 no. 13) reviews the many studies in the field, and the picture is quite damning.
I reproduce the table here, but you can access the full article freely. The important column is Risk: RR means relative risk, which roughly translate into how more likely is a light-smoker to develop the disease compared to a non-smoker. If the number is 1, it means light smokers and non-smokers face the same risks. The further away from 1 the number is, the shittier it is for light smokers.
| Disease | Level of Smoking | Risk for Light Smokers vs Nonsmokers | Study Design |
|---|---|---|---|
| Cig indicates cigarettes; RR, relative risk; OR, odds ratio; and RH, relative hazard. | |||
| Cardiovascular disease | |||
| Ischemic heart disease28 | 1–4 cig/d | RR 2.74 (2.07–3.61) in men; RR 2.94 (1.75–4.95) in women | Prospective cohort |
| Aortic aneurysm30 | <10 cig/d | RR 2.29 | Prospective cohort |
| Cardiovascular mortality31 | Occasional smoking | RR 1.5 in men (1.0–2.3) | Prospective cohort |
| Malignancy | |||
| Esophageal cancer32 | 1–14 cig/d | RR 4.25 | Prospective cohort |
| Lung cancer28 | 1–4 cig/d | RR 2.79 (0.94–8.28) in men; RR 5.03 (1.81 to 13.98) in women | Prospective cohort |
| Gastric cancer33 | 1–4 cig/d | RR 2.4 (1.3–4.3) | Case control |
| Pancreatic cancer34 | <10 cig/d | RR 1.8 (1.4–2.5) | Prospective cohort |
| Respiratory diseases | |||
| Lower respiratory tract infections35 | Light smoking (<1 pack/d) | RR:1.5 in men; RR 1.13 in women | Prospective cohort |
| Prolonged duration of respiratory symptoms: cough35 | <1 pack/d | Duration of respiratory symptoms (cough) was 7.7 d in the light smoking group vs 6.8 d in never smokers | Prospective cohort |
| Reproductive health | |||
| Impaired fecundity in women (delayed time to conception)36 | 1–4 cig/d | Increasing OR of delayed conception from 1.1 for 6-mo delay to 3.2 at 18-mo delay | Prospective cohort |
| Spermatozoa function36 | 4 cig/d for 5 y | Spermatozoa showed decreased density/motility | Prospective cohort |
| Placenta previa37 | Light smoking (<1 pack/d) | OR 2.2 (0.87–7.83) | Case control |
| Ectopic pregnancy38 | <10 cig/day | OR 1.4 (0.8–2.5) | Case control |
| Other conditions | |||
| Ankle fractures in women39 | 1–10 cig/d | OR 3.0 (1.9–4.6) | Retrospective |
| Cataracts/development of nuclear lens opacities40 | Light smoking (<10 cig/d) | OR 1.68 (1.14–2.49) | Prospective cohort |
| Physical disability after meniscal tear41 | Light smoking (<1 pack/d) | RH 1.44 (1.07–1.94) | Prospective cohort |
| All-cause mortality | |||
| Risk of all-cause mortality in men31 | Occasional smoking | OR 1.6 (1.3–2.1) | Prospective cohort |
The table offers a synthesis of many studies found in the scientific literature addressing the issue of light smokers. There are limitations as to what those studies can do, for example one cannot devise a randomised controlled trial of smoking for obvious ethical reasons. But suffice to say that most of the studies they cite do control for confounding factors such as diet, exercise, wealth, etc.
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New post: Light smokers still at risk http://t.co/OTCoqMRr