少量の長期喫煙で死亡リスク上昇
少量の長期喫煙で死亡リスク上昇
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米国29万人の大規模前向きコホート研究
米国29万人の大規模前向きコホート研究
1日1本未満という少量の喫煙でも長期間継続することで全死亡リスクが1.64倍に高まることが米国の大規模前向きコホート研究によって明らかになった。米・National Cancer InstituteのMaki Inoue-Choi氏らがJAMA Internal Medicine に発表した。
肺がんリスクは1日1本未満でも9.12倍
肺がんリスクは1日1本未満でも9.12倍
喫煙による健康被害は世界的な問題となっており、世界の喫煙関連死は毎年500万人に上るとされる。一方、少量の喫煙を長期間続けた場合の影響を明らかにした研究は少なく、そのため一部に、少量の喫煙であれば安全であるとの認識もみられている。
Inoue-Choi氏らは、前向きコホート研究である米国立衛生研究所（NIH）のAARP Diet and Health研究に参加した成人のうち、2004～05年のアンケートに回答した29万215人（59～82歳）を対象に、1日当たり1本未満または1～10本の少量喫煙を長期間続けた場合に、全死亡および喫煙関連の疾患死亡にどのような影響があるかを非喫煙者との比較で検討した。
2004～05年時点での喫煙者は7.7％、過去に喫煙歴のあるものが53.9％、非喫煙者が38.4％であり、現在の喫煙者のうち6.8％が1本未満/日、30.4％が1～10本/日の少量喫煙者だった。過去の喫煙歴については、アンケートにより、15歳未満から70歳以上までの各年齢層における喫煙量に関する情報を収集した。その結果、少量喫煙者の多くが、それ以前はより多量の喫煙をしており、結局、過去から継続して少量喫煙を継続していたのは、1本未満/日の喫煙者では159例（9.1％）、1～10本/日の喫煙者では1,493例（22.5％）だった。
同研究では平均6.6年の追跡において、3万7,331人の死亡が確認された。非喫煙者に対する少量喫煙継続者の全死亡リスク（HR）は、1本未満/日で1.64、1～10本/日で1.87と高かった。
また、喫煙が関連するとされる疾患での死亡リスクは、特に肺がん死リスクは1本未満/日で9.12、1～10本/日で11.61と高く、少量継続喫煙との強い関連性が示された。いずれのリスクにおいても男女とも同様の傾向が認められている。
禁煙年齢早いほどリスクは低下
禁煙年齢早いほどリスクは低下
また同研究では、これら少量喫煙継続者においては、禁煙した年齢が若いほど死亡リスクが低くなることも示され、例えば50歳以上で禁煙した場合の全死亡リスクは1本未満/日が1.44、1～10本/日が1.42と、それよりも若い年齢で禁煙した場合より高かった。
以上から、Inoue-Choi氏らは「今回の結果は、喫煙における安全量はないことのさらなるエビデンスとなるものであり、1日の喫煙量がどれだけ少なくても、全ての喫煙者が禁煙を目指すべきである」と結論付けている。
JAMA Intern Med. 2017 Jan 1;177(1):87-95. doi: 10.1001/jamainternmed.2016.7511.
Association of Long-term, Low-Intensity Smoking With All-Cause and Cause-Specific Mortality in the National Institutes of Health-AARP Diet and Health Study.
Association of Long-term, Low-Intensity Smoking With All-Cause and Cause-Specific Mortality in the National Institutes of Health-AARP Diet and Health Study.
Inoue-Choi M1, Liao LM1, Reyes-Guzman C2, Hartge P1, Caporaso N1, Freedman ND1.
Abstract
A growing proportion of US smokers now smoke fewer than 10 cigarettes per day (CPD), and that proportion will likely rise in the future. The health effects of smoking only a few CPD over one's lifetime are less understood than are the effects of heavier smoking, although many smokers believe that their level is modest.
To evaluate the associations of long-term smoking of fewer than 1 or 1 to 10 CPD (low intensity) with all-cause and cause-specific mortality compared with never smoking cigarettes.
Prospective cohort study of 290 215 adults in the National Institutes of Health-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study who were aged 59 to 82 years in calendar years 2004-2005 (baseline). Data were gathered with a questionnaire assessing lifetime cigarette smoking history. Hazard ratios (HRs) and 95% CIs were determined for all-cause mortality and cause-specific mortality through the end of 2011. Hazard ratios and 95% CIs were estimated using Cox proportional hazards regression models using age as the underlying time metric and adjusted for sex, race/ethnicity, educational level, physical activity, and alcohol intake. Data analysis was conducted from December 15, 2015, to September 30, 2016.
Current and historical smoking intensity during 9 previous age periods (from <15 years to ≥70 years) over the lifetime assessed on the 2004-2005 questionnaire.
All-cause and cause-specific mortality among current, former, and never smokers.
Of the 290 215 cohort participants who completed the 2004-2005 questionnaire, 168 140 were men (57.9%); the mean (SD) age was 71 (5.3) years (range, 59-82 years). Most people who smoked fewer than 1 or 1 to 10 CPD at baseline reported smokingsubstantially higher numbers of CPD earlier in their lives. Nevertheless, 159 (9.1%) and 1493 (22.5%) of these individuals reported consistently smoking fewer than 1 or 1 to 10 CPD in each age period that they smoked, respectively. Relative to never smokers, consistent smokers of fewer than 1 CPD (HR, 1.64; 95% CI, 1.07-2.51) and 1 to 10 CPD (HR, 1.87; 95% CI, 1.64-2.13) had a higher all-cause mortality risk. Associations were similar in women and men for all-cause mortality and were observed across a range of smoking-related causes of death, with an especially strong association with lung cancer (HR, 9.12; 95% CI, 2.92-28.47, and HR, 11.61; 95% CI, 8.25-16.35 for <1 and 1-10 CPD, respectively). Former smokers who had consistently smoked fewer than 1 or 1 to 10 CPD had progressively lower risks with younger age at cessation. For example, the HRs for consistent smokers of fewer than 1 and 1 to 10 CPD who quit at 50 years or older were 1.44 (95% CI, 1.12-1.85) and 1.42 (95% CI, 1.27-1.59), respectively.
This study provides evidence that individuals who smoke fewer than 1 or 1 to 10 CPD over their lifetime have higher mortality risks than never smokers and would benefit from cessation. These results provide further evidence that there is no risk-free level of exposure to tobacco smoke.
PMID: 27918784 PMCID: PMC5555224 DOI: 10.1001/jamainternmed.2016.7511
Int J Cancer. 2018 Jan 15;142(2):271-280. doi: 10.1002/ijc.31059. Epub 2017 Oct 10.
Association between long-term low-intensity cigarette smoking and incidence of smoking-related cancer in the national institutes of health-AARP cohort.
Association between long-term low-intensity cigarette smoking and incidence of smoking-related cancer in the national institutes of health-AARP cohort.
Inoue-Choi M1, Hartge P1, Liao LM1, Caporaso N1, Freedman ND1.
Abstract
An increasing proportion of US smokers smoke ≤10 cigarettes per day (CPD) or do not smoke every day, yet the health effects of low-intensity smoking are poorly understood. We identified lifelong smokers of <1 or 1-10 CPD and evaluated risk of incident cancer among 238,525 cancer-free adults, aged 59-82, in the NIH-AARP Diet and Health Study. A questionnaire administered in 2004-2005 assessed CPD during nine age-periods (<15 to ≥70). We estimated hazard ratios (HR) and 95% confidence intervals (CI) using multivariable-adjusted Cox proportional hazards regression with age as the underlying time metric. Of the 18,233 current smokers, (7.6%), 137 and 1,243 reported consistently smoking <1 CPD and 1-10 CPD, respectively. Relative to never smokers, current smokers who reported consistently smoking 1-10 CPD over their lifetime were 2.34 (95% CI = 1.86-2.93) times more likely to develop smoking-related cancer. Current lifetime smokers of <1 CPD were 1.89 (95% CI = 0.90-3.96) times more likely to develop tobacco-related cancer, although the association did not reach statistical significance. Associations were observed for lifelong smoking of ≤10 CPD with lung cancer (HR = 9.65, 95% CI = 6.93-13.43); bladder cancer (HR = 2.22, 95% CI = 1.22-4.05); and pancreatic cancer (HR = 2.03, 95%CI: 1.05-3.95). Among lifelong ≤10 CPD smokers, former smokers had lower risks of smoking-related cancer with longer time since cessation and longer smoking duration. Lifelong <1 and 1-10 CPD smokers are at increased risk of incident cancer relative to never smokers and would benefit from cessation, providing further evidence that even low-levels of cigarette smoking cause cancer.
cigarette; incident cancer; lifetime smoking; low-intensity smoking
PMID: 28929489 PMCID: PMC5748934 [Available on 2019-01-15] DOI: 10.1002/ijc.31059
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