Mortensen Erik Lykke, Hell Kristine, Okholm Gunhild Tidemann, Flensborg-Madsen Trine, Grønkjær Marie
Unit of Medical Psychology, Section of Environmental Health, Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.
PLoS One. 2025 Mar 19;20(3):e0319839. doi: 10.1371/journal.pone.0319839. eCollection 2025.
Most previous studies of effects of smoking on age-related cognitive decline have compared cognitive decline in current smokers, former smokers, and never smokers rather than investigating the effects of pack-years. The aim of the present study was to analyze the association between smoking and age-related cognitive decline in a sample of men administered the same intelligence test in young adulthood and late midlife, using pack-years between the two assessments as the primary measure of exposure to smoking.
In 5052 men, scores on a military intelligence test (BPP, Børge Priens Prøve) were available from young adulthood and a late midlife follow-up assessment including the same intelligence test and a comprehensive questionnaire on socio-demographic factors, lifestyle, and health. Information on smoking was self-reported at follow up for eight age periods, and pack-years were calculated from age 19 based on information on daily smoking and the duration of each age period. The differences in cognitive decline between adult-life smokers and non-smokers and the differences between light, moderate, and heavy smokers defined by pack-years were analyzed in linear regression models.
All smoking variables were only weakly associated with cognitive decline. Comparison of adult-life smokers and non-smokers showed less cognitive decline among smokers (1.12 IQ points, p < 0.001). Among smokers, analyses of pack-years suggested a weak dose-response relationship with more decline in heavy smokers than in light smokers (1.33 IQ points, p = 0.001). Independent of pack-years, current smoking was associated with larger cognitive decline than former smoking (1.73 IQ points, p < 0.001).
Smoking explained negligible fractions of the variance in cognitive decline, and thus our results did not indicate that smoking is a strong predictor of cognitive decline. The effects of pack-years suggest a relatively weak, possibly cumulative effect of smoking across the adult lifespan. The difference in decline between smokers and non-smokers may reflect participation bias and selective attrition at follow-up while the effects of current smoking may reflect either temporary effects of smoking or individual and life-style characteristics associated with continuation of smoking into late midlife.
以往大多数关于吸烟对与年龄相关的认知衰退影响的研究，比较的是当前吸烟者、既往吸烟者和从不吸烟者的认知衰退情况，而非调查吸烟包年数的影响。本研究的目的是，在一个于青年期和中年后期接受了相同智力测试的男性样本中，分析吸烟与年龄相关的认知衰退之间的关联，将两次评估之间的吸烟包年数作为接触吸烟的主要衡量指标。
在5052名男性中，可获取其青年期军事智力测试（BPP，博尔格·普里恩斯测试）的分数，以及中年后期随访评估的分数，该评估包括相同的智力测试和一份关于社会人口学因素、生活方式及健康状况的综合问卷。在随访中，通过自我报告获取了八个年龄段的吸烟信息，并根据每日吸烟情况和每个年龄段的时长，从19岁开始计算吸烟包年数。在线性回归模型中，分析了成年期吸烟者与非吸烟者之间的认知衰退差异，以及根据吸烟包年数定义的轻度、中度和重度吸烟者之间的差异。
所有吸烟变量与认知衰退的关联都很弱。成年期吸烟者与非吸烟者的比较显示，吸烟者的认知衰退较少（1.12个智商点，p < 0.001）。在吸烟者中，对吸烟包年数的分析表明存在弱剂量反应关系，重度吸烟者的衰退比轻度吸烟者更多（1.33个智商点，p = 0.001）。独立于吸烟包年数，当前吸烟与比既往吸烟更大的认知衰退相关（1.73个智商点，p < 0.001）。
吸烟对认知衰退方差的解释比例可忽略不计，因此我们的结果并未表明吸烟是认知衰退的强预测因素。吸烟包年数的影响表明，吸烟在整个成年期的影响相对较弱，可能具有累积效应。吸烟者与非吸烟者之间衰退的差异可能反映了随访中的参与偏倚和选择性损耗，而当前吸烟的影响可能反映了吸烟的暂时效应，或与持续吸烟至中年后期相关的个体及生活方式特征。
