Lubin Jay H, Couper David, Lutsey Pamela L, Woodward Mark, Yatsuya Hiroshi, Huxley Rachel R
From the aScientist Emeritus, Biostatistics Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD; bClinical Professor and Deputy Director, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC; cAssistant Professor, Division of Epidemiology and Community Health, University of Minnesota School of Public Health, Minneapolis, MN; dProfessor of Biostatistics, The George Institute for Global Health, Nuffield Department of Population Health, University of Oxford, Oxford, United Kingdom; eThe George Institute for Global Health, University of Sydney, Sydney, NSW, Australia; fDepartment of Epidemiology, Johns Hopkins University, Baltimore, MD; gProfessor, Department of Public Health, Fujita Health University School of Medicine Toyoake Aichi, Japan; and hProfessor, School of Public Health, Curtin University, Perth, Australia.
Epidemiology. 2016 May;27(3):395-404. doi: 10.1097/EDE.0000000000000437.
Relative risks (RRs) for cardiovascular disease (CVD) by smoking rate exhibit a concave pattern, with RRs in low rate smokers exceeding a linear extrapolation from higher rate smokers. However, cigarettes/day does not by itself fully characterize smoking-related risks. A reexamination of the concave pattern using a comprehensive representation of smoking may enhance insights.
Data were from the Atherosclerosis Risk in Communities (ARIC) Study, a prospective cohort enrolled in four areas of the US in 1987-1989. Follow-up was through 2008. Analyses included 14,233 participants, 245,915 person-years, and 3,411 CVD events.
The concave RRs with cigarettes/day were consistent with cigarettes/day modifying a linear RR association of pack-years with CVD (i.e., strength of the pack-years association depended on cigarettes/day, indicating that the manner of pack-years accrual impacted risk). Smoking fewer cigarettes/day for longer duration was more deleterious than smoking more cigarettes/day for shorter duration (P < 0.01). For 50 pack-years (365,000 cigarettes), estimated RRs of CVD were 2.1 for accrual at 20 cigarettes/day and 1.6 for accrual at 50 cigarettes/day. Years since smoking cessation did not alter the diminishing strength of association with increasing cigarettes/day. Analyses that accounted for competing risks did not affect findings.
Pack-years remained the primary determinant of smoking-related CVD risk; however, accrual influenced RRs. For equal pack-years, smoking fewer cigarettes/day for longer duration was more deleterious than smoking more cigarettes/day for shorter duration. This observation provides clues to better understanding the biological mechanisms, and reinforces the importance of cessation rather than smoking less to reduce CVD risk.
心血管疾病（CVD）的相对风险（RRs）与吸烟率呈现出一种凹形模式，低吸烟率者的RRs超过了根据高吸烟率者进行线性外推得出的值。然而，每日吸烟量本身并不能完全表征与吸烟相关的风险。使用吸烟的综合表征对这种凹形模式进行重新审视可能会加深理解。
数据来自社区动脉粥样硬化风险（ARIC）研究，这是一项于1987 - 1989年在美国四个地区招募的前瞻性队列研究。随访至2008年。分析纳入了14,233名参与者、245,915人年以及3,411例心血管疾病事件。
每日吸烟量呈现的凹形RRs与每日吸烟量改变吸烟包年数与心血管疾病的线性RR关联一致（即，吸烟包年数关联的强度取决于每日吸烟量，表明吸烟包年数的累积方式影响风险）。较长时间每日吸较少的烟比较短时间每日吸较多的烟危害更大（P < 0.01）。对于50吸烟包年（365,000支香烟），每日吸20支香烟累积时心血管疾病的估计RR为2.1，每日吸50支香烟累积时为1.6。戒烟后的年数并未改变随着每日吸烟量增加关联强度减弱的情况。考虑竞争风险的分析未影响研究结果。
吸烟包年数仍然是与吸烟相关的心血管疾病风险的主要决定因素；然而，累积方式影响RRs。对于相同的吸烟包年数，较长时间每日吸较少的烟比较短时间每日吸较多的烟危害更大。这一观察结果为更好地理解生物学机制提供了线索，并强化了戒烟而非减少吸烟以降低心血管疾病风险的重要性。
