5/1/2023 0 Comments Starters orders 6 review![]() While some meta-analyses of the evidence have been published in recent years none consider more than a relatively small fraction of the published evidence. Further reports have defined the relationship in more detail, and it has been estimated that, in the United States, 90% of male lung cancer deaths and 75%-80% of female lung cancer deaths are caused by smoking. ![]() This led the US Surgeon General to conclude in 1964 that “cigarette smoking is a cause of lung cancer in men, and a suspected cause of lung cancer in women”. An association was clearly documented in case–control studies conducted in Germany in the 1930s, and in the United States and Great Britain in the 1950s, and was strengthened by surveys of large cohorts. It has been known for many years that smoking causes lung cancer. ![]() Our results quantify the relationships more precisely than previously. This emphasises the causal nature of the relationship. The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. Covariate-adjustment little affected RR estimates. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Relationships were somewhat stronger in later starting and larger studies. It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). ResultsĢ87 studies (20 subsidiary) were identified. ![]() Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma (“squamous”) and adenocarcinoma (“adeno”). RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose–response. Data were extracted on design, exposures, histological types and confounder adjustment. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. We summarize evidence for various indices. Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. ![]()
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