Neurocognitive studies of chronic smoking in adults (sorted by age group, then year of publication).
The vast majority of research investigating the neurocognitive consequences of chronic cigarette smoking is cross-sectional in design and focused primarily on middle-aged and older adults. In the sole study of adolescents, daily smokers (mean age = 17 ± 1) showed deficits in accuracy of working memory relative to NSC, with individuals who began smoking at a younger age demonstrating greater impairment than those who began smoking at a later age [23
]. In the few studies with young adults, smokers were inferior to NSC on measures of sustained attention and impulse control [24
], auditory-verbal memory, oral arithmetic, and receptive and expressive vocabulary [25
], information processing speed [26
] and general intelligence [27
]. On an experimental behavioral measure of risk-taking (Balloon Analogue Risk Task [28
]), young adults smokers demonstrated higher levels of risk-taking [29
]. In cross-sectional studies specifically comparing NSC to middle-aged and/or older adult smokers, poorer performance in smokers was reported for auditory-verbal learning and/or memory [30
], working memory [26
], executive functions [33
], general intellectual abilities [39
], visual search speed [40
], processing speed and cognitive flexibility [30
] and global cognitive function (e.g., brief mental status examinations such as the MMSE) [41
]. In a middle-aged cohort of combined current and former smokers, any history of smoking was associated with increased risk for abnormal auditory-verbal memory [43
]. Some studies observed the performance of former smokers fell between that of current smokers and NSC in young [25
], middle-aged and older adults [31
]. Other studies found no differences between former smokers and NSC [25
]. The inconsistencies among these studies may be related to the substantial variety of measures used across studies to evaluate the domain of functioning in question as well as inconsistency in the magnitude of neurocognitive dysfunction in the smoking study cohort.
In cross-sectional population-based studies with community-dwelling older adults, where smoking status (i.e.
, current smoker, past smoker, never smoker) was used as a prospective or retrospective predictor, current smoking [44
] and any history of smoking [47
] were associated with poorer performances on measures of global cognitive function. Any previous smoking history (with variable lengths of smoking cessation) was associated with poorer cognitive flexibility [45
], and impaired general cognitive function [44
] or, conversely, decreased risk of global cognitive impairment [46
]. Chronic smoking in older adults has also been associated with a diminished ability to execute some activities of daily living [48
] and compromised postural stability [49
Longitudinal research with non-demented, population-based samples found that current cigarette smokers demonstrated an abnormal rate of decline on indices of reasoning [43
] and auditory-verbal memory [40
] in middle aged adults, and abnormal decline on measures of global cognitive function [47
] and auditory-verbal memory in older adults [54
Sex effects in neurocognition among smokers have also been addressed in some studies. Edelstein et al.
] found no differences between older adult male smokers and male NSC on measures of global cognitive functioning, set-shifting, semantic fluency and auditory-verbal and visuospatial learning and memory, while older adult female smokers demonstrated poorer global cognitive functioning and auditory-verbal memory than female NSC. Jacobsen and colleagues [23
] reported that male adolescent smokers performed more poorly than did female smokers on measures of selective and divided attention. Similarly, Razani and colleagues [37
] observed that sex was a significant predictor of non-verbal abstraction in currently smoking older adults, however, no interactions were reported among sex, smoking status or smoking severity. Other studies, however, have found no sex effects on neurocognition in middle aged and older adults [32
The level and chronicity of smoking, as reflected in the number of cigarettes smoked per day, duration of smoking over lifetime, and/or dose-duration (i.e.
, pack-years) were inversely related to various domains of neurocognition in adults across a wide age range [25
]. Several reports indicate chronic smoking is associated with increased risk for various forms of dementia, in particular Alzheimer’s Disease and vascular dementia [57
]. This risk may be modulated through the apolipoprotein E
4 (ApoE4) genotype, a known genetic risk for the development of Alzheimer’s Disease [52
]. Interestingly, some studies have reported that risk for development of Alzheimer’s Disease was greater in smokers who were not
ApoE4 carriers [52
Several studies, smoking status (i.e.
, smoker or non-smoker) or measures of smoking consumption (e.g., pack years), showed weak or no relationships to specific neurocognitive functions (e.g., measures of learning and memory, mental arithmetic, verbal fluency, processing speed), global neurocognitive function (e.g., MMSE) and neurocognitive decline in young and middle aged adults [62
] and in large community-based samples consisting of middle-aged and older adults [64