Low cigarette consumption and risk of coronary heart disease and stroke: meta-analysis of 141 cohort studies in 55 study reports.

Hackshaw A,  Morris JK, Boniface S, Tang JL, Milenković D. BMJ. 2018;360:j5855. [CrossRef] [PubMed]

It is well known that the more cigarettes smoked per day, the greater the health risk. Based on this principle, many have assumed that smoking one or two cigarettes a day carried little risk, i.e., only about 5-10% of the risk of smoking 20 cigarettes (1 pack) per day. However, investigators from the UK challenged that assumption. The authors performed a meta-analysis and found that among men, the pooled relative risk for coronary heart disease was 1.48 for smoking one cigarette per day and 2.04 for 20 cigarettes per day. Among women, the pooled relative risks were 1.57 and 2.84 for one and 20 cigarettes per day. For stroke, the pooled relative risks were 1.25 and 1.64 for smoking one or 20 cigarettes for men per and 1.31 and 2.16 for women. The study is strongly suggestive that the only way to eliminate the risk from smoking is to quit.