Cigarette smoking and cognitive decline in midlife: evidence from a prospective birth cohort study

Cigarette smoke and related risk factors in neurological disorders: An update

Cigarette smoking is known to be harmful to health, and is considered the main cause of death worldwide, especially in India. Among the well-distinguished diseases related to smoking are, chronic obstructive pulmonary disease, oral and peripheral cancers, and cardiovascular complications. However, the impact of cigarette smoking on neurocognitive and neuropathological effects, including anxiety, Alzheimer's disease, Parkinson's disease, ischemic stroke, and blood-brain barrier dysfunction, still remains unclear. Cigarette smoke consists of more than 4500 toxic chemicals that combine to form free radicals, which lead to oxidative stress-associated neurological disorders. Herein, we discuss the role of antioxidant agents in delaying or attenuating disease complications. In addition, in this review, we discuss the neuropathological effect of cigarette smoke and its interference in neurodegeneration.

Spatial short-term memory is impaired in dependent betel quid chewers

RATIONAL

Betel quid is regarded as a human carcinogen by the World Health Organization. It remains unknown whether chewing betel quid has a chronic effect on healthy betel quid chewers' memory.

OBJECTIVES

The present study aims to investigate whether chewing betel quid can affect short-term memory (STM).

METHODS

Three groups of participants (24 dependent chewers, 24 non-dependent chewers, and 24 non-chewers) were invited to carry out the matrix span task, the object span task, and the digit span task. All span tasks' results were adopted to assess spatial STM, visual STM, and verbal STM, respectively. Besides, there are three set sizes (small, medium, and large) in each span task.

RESULTS

For the matrix span task, results showed that the dependent chewers had worse performances than the non-dependent chewers and the non-chewers at medium and large set sizes. For the object span task and digit span task, there were no differences in between groups. In each group, recognition performances were worse with the increasing set size and showing successful manipulation of memory load.

CONCLUSIONS

The current study provided the first evidence that dependent betel quid chewing can selectively impair spatial STM rather than visual STM and verbal STM. Theoretical and practical implications of this result are discussed.

Cognitive Dysfunction, Affective States, and Vulnerability to Nicotine Addiction: A Multifactorial Perspective

Although smoking prevalence has declined in recent years, certain subpopulations continue to smoke at disproportionately high rates and show resistance to cessation treatments. Individuals showing cognitive and affective impairments, including emotional distress and deficits in attention, memory, and inhibitory control, particularly in the context of psychiatric conditions, such as attention-deficit hyperactivity disorder, schizophrenia, and mood disorders, are at higher risk for tobacco addiction. Nicotine has been shown to improve cognitive and emotional processing in some conditions, including during tobacco abstinence. Self-medication of cognitive deficits or negative affect has been proposed to underlie high rates of tobacco smoking among people with psychiatric disorders. However, pre-existing cognitive and mood disorders may also influence the development and maintenance of nicotine dependence, by biasing nicotine-induced alterations in information processing and associative learning, decision-making, and inhibitory control. Here, we discuss the potential forms of contribution of cognitive and affective deficits to nicotine addiction-related processes, by reviewing major clinical and preclinical studies investigating either the procognitive and therapeutic action of nicotine or the putative primary role of cognitive and emotional impairments in addiction-like features.

Lower subcortical gray matter volume in both younger smokers and established smokers relative to non-smokers

Although established adult smokers with long histories of nicotine dependence have lower neural tissue volume than non-smokers, it is not clear if lower regional brain volume is also observed in younger, less established smokers. The primary goal of this study was to investigate neural tissue volume in a large group of smokers and non-smokers, with a secondary goal of measuring the impact of age on these effects. We used voxel-based morphometry to compare regional gray matter volume in 118 individuals (59 smokers, 59 age- and gender-matched non-smokers). Younger smokers had significantly lower gray matter volume in the left thalamus and the left amygdala than their non-smoking peers (family-wise error-corrected clusters, P < 0.05). There was no correlation between smoking use variables and tissue volume among younger smokers. Established smokers had significantly lower gray matter volume than age-matched non-smokers in the insula, parahippocampal gyrus and pallidum. Medial prefrontal cortex gray matter volume was negatively correlated with pack-years of smoking among the established smokers, but not the younger smokers. These data reveal that regional tissue volume differences are not limited exclusively to established smokers. Deficits in young adults indicate that cigarette smoking may either be deleterious to the thalamus and amygdala at an earlier age than previously reported, or that pre-existing differences in these areas may predispose individuals to the development of nicotine dependence.

Child Neglect and Maltreatment and Childhood-to-Adulthood Cognition and Mental Health in a Prospective Birth Cohort

OBJECTIVE

Life-long adverse effects of childhood maltreatment on mental health are well established, but effects on child-to-adulthood cognition and related educational attainment have yet to be examined in the general population. We aimed to establish whether different forms of child maltreatment are associated with poorer cognition and educational qualifications in childhood/adolescence and whether associations persist to midlife, parallel to associations for mental health.

METHOD

Cognitive abilities at ages 7, 11, and 16 years (math, reading, and general intellectual ability) and 50 years (immediate/delayed memory, verbal fluency, processing speed) were assessed using standardized tests, and qualifications by age 42 were self-reported. Information on childhood maltreatment (neglect and abuse: sexual, physical, psychological, witnessed), cognition, and mental health was available for 8,928 participants in the 1958 British Birth Cohort.

RESULTS

We found a strong association of child neglect with cognitive deficits from childhood to adulthood. To illustrate, the most neglected 6% of the population (score ≥4) had a 0.60 (95% CI = 0.56-0.68) SD lower cognitive score at age 16 and a 0.28 (95% CI = 0.20-0.36) SD deficit at age 50 years relative to the non-neglected participants (score = 0) after adjustment for confounding factors and mental health, and they also had increased risk of poor qualifications (i.e., none/low versus degree-level). Childhood neglect and all forms of abuse were associated with poorer child-to-adulthood mental health, but abuse was mostly unrelated to cognitive abilities.

CONCLUSION

The study provides novel data that child neglect is associated with cognitive deficits in childhood/adolescence and decades later in adulthood, independent of mental health, and highlights the lifelong burden of child neglect on cognitive abilities and mental health.

Impact of Quantified Smoking Status on Cognition in Young Adults

INTRODUCTION

Cigarette smoking is an addictive behaviour which continues to rise among young adults. It has been associated with various health hazards. Effect of smoking on cognitive function has been contradicting. Thus our aim was to compare cognitive performances between smokers and non smokers and also to observe the effect of varying intensity of smoking on cognition.

MATERIALS AND METHODS

This is a cross-sectional study. Thirty non smokers, 30 mild smokers, 30 moderate smokers, 30 heavy smokers within the age group of 25-35 years were involved in the study. Their cognitive performance were assessed by digit symbol substitution test (DSST), digit vigilance test (DVT), visual reaction time (VRT), letter cancellation test (LCT), word recall (WR), and object recall (OR).

RESULT

The cognitive data were analysed using unpaired students t-test and ANOVA in SPSS 19. Smokers showed significant decline in their cognitive performances when compared to smokers (p ≤ 0.05). Mild smokers showed significantly better performance in the DSST, DVT and VRT tests than the non smokers. This indicates the attention and alertness were better in mild smokers than the non smokers. With the increase in the intensity of smoking cognitive performances were also significantly declined.

CONCLUSION

Thus the study indicates decreased cognitive performances in young adult smokers.

Demographic and Lifestyle Characteristics, but Not Apolipoprotein E Genotype, Are Associated with Intelligence among Young Chinese College Students

BACKGROUND

Intelligence is an important human feature that strongly affects many life outcomes, including health, life-span, income, educational and occupational attainments. People at all ages differ in their intelligence but the origins of these differences are much debated. A variety of environmental and genetic factors have been reported to be associated with individual intelligence, yet their nature and contribution to intelligence differences have been controversial.

OBJECTIVE

To investigate the contribution of apolipoprotein E (APOE) genotype, which is associated with the risk for Alzheimer's disease, as well as demographic and lifestyle characteristics, to the variation in intelligence.

METHODS

A total of 607 Chinese college students aged 18 to 25 years old were included in this prospective observational study. The Chinese revision of Wechsler Adult Intelligence Scale (the fourth edition, short version) was used to determine the intelligence level of participants. Demographic and lifestyle characteristics data were obtained from self-administered questionnaires.

RESULTS

No significant association was found between APOE polymorphic alleles and different intelligence quotient (IQ) measures. Interestingly, a portion of demographic and lifestyle characteristics, including age, smoking and sleep quality were significantly associated with different IQ measures.

CONCLUSIONS

Our findings indicate that demographic features and lifestyle characteristics, but not APOE genotype, are associated with intelligence measures among young Chinese college students. Thus, although APOE ε4 allele is a strong genetic risk factor for Alzheimer's disease, it does not seem to impact intelligence at young ages.

Mechanisms of Action and Persistent Neuroplasticity by Drugs of Abuse

Adaptation of the nervous system to different chemical and physiologic conditions is important for the homeostasis of brain processes and for learning and remembering appropriate responses to challenges. Although processes such as tolerance and dependence to various drugs of abuse have been known for a long time, it was recently discovered that even a single pharmacologically relevant dose of various drugs of abuse induces neuroplasticity in selected neuronal populations, such as the dopamine neurons of the ventral tegmental area, which persist long after the drug has been excreted. Prolonged (self-) administration of drugs induces gene expression, neurochemical, neurophysiological, and structural changes in many brain cell populations. These region-specific changes correlate with addiction, drug intake, and conditioned drugs effects, such as cue- or stress-induced reinstatement of drug seeking. In rodents, adolescent drug exposure often causes significantly more behavioral changes later in adulthood than a corresponding exposure in adults. Clinically the most impairing and devastating effects on the brain are produced by alcohol during fetal development. In adult recreational drug users or in medicated patients, it has been difficult to find persistent functional or behavioral changes, suggesting that heavy exposure to drugs of abuse is needed for neurotoxicity and for persistent emotional and cognitive alterations. This review describes recent advances in this important area of research, which harbors the aim of translating this knowledge to better treatments for addictions and related neuropsychiatric illnesses.

Thyroid hormone signaling: Contribution to neural function, cognition, and relationship to nicotine

Cigarette smoking is common despite its adverse effects on health, such as cardiovascular disease and stroke. Understanding the mechanisms that contribute to the addictive properties of nicotine makes it possible to target them to prevent the initiation of smoking behavior and/or increase the chance of successful quit attempts. While highly addictive, nicotine is not generally considered to be as reinforcing as other drugs of abuse. There are likely other mechanisms at work that contribute to the addictive liability of nicotine. Nicotine modulates aspects of the endocrine system, including the thyroid, which is critical for normal cognitive functioning. It is possible that nicotine's effects on thyroid function may alter learning and memory, and this may underlie some of its addictive potential. Here, we review the literature on thyroid function and cognition, with a focus on how nicotine alters thyroid hormone signaling and the potential impact on cognition. Changes in cognition are a major symptom of nicotine addiction. Current anti-smoking therapies have modest success at best. If some of the cognitive effects of nicotine are mediated through the thyroid hormone system, then thyroid hormone agonists may be novel treatments for smoking cessation therapies. The content of this review is important because it clarifies the relationship between smoking and thyroid function, which has been ill-defined in the past. This review is timely because the reduction in smoking rates we have seen in recent decades, due to public awareness campaigns and public smoking bans, has leveled off in recent years. Therefore, novel treatment approaches are needed to help reduce smoking rates further.

Regulation of α4β2α5 nicotinic acetylcholinergic receptors in rat cerebral cortex in early and late adolescence: Sex differences in response to chronic nicotine

Chronic nicotine administration in animals, and smoking in humans, causes up-regulation of α4β2* neuronal nicotinic receptors (nAChRs), which has been hypothesized to contribute to the addictive actions of nicotine. We used a rat model to test whether such up-regulatory effects differ in adolescents versus adults, and in males versus females. Following chronic treatment with nicotine or saline via subcutaneous osmotic minipumps, we measured α4β2 and α4β2α5 nAChRs in cerebral cortex using [3H]epibatidine to label assembled nAChRs, and selective antibodies to measure the individual subunits via immunoprecipitation. For the first time, we provide a detailed characterization of the response of both α4β2 and α4β2α5 nAChRs in female adolescent rat cerebral cortex. We found differences in nicotine-induced up-regulation between males and females in early adolescence that are absent in both late adolescence and adulthood. Males showed significant up-regulation at PN28 which was absent in age-matched females. These results demonstrate sex differences in the susceptibility of α4β2* nAChRs to the effects of chronic nicotine exposure in the cerebral cortex based on age.

Altered brain functional networks in heavy smokers

Recent neuroimaging studies have demonstrated that cigarette smoking is associated with changed brain structure and function. However, little is known about alterations of the topological organization of brain functional networks in heavy smokers. Thirty-one heavy smokers and 33 non-smokers underwent a resting-state functional magnetic resonance imaging scan. The whole-brain functional networks were constructed by thresholding the correlation matrices of 90 brain regions and their topological properties were analyzed using graph network analysis. Non-parametric permutation tests were performed to investigate group differences in network topological measures and multiple regression analysis was conducted to determine the relationships between the network metrics and smoking-related variables. Both heavy smokers and non-smokers exhibited small-world architecture in their brain functional networks. Compared with non-smokers, however, heavy smokers showed altered topological measurements characterized by lower global efficiency, higher local efficiency and clustering coefficients and greater path length. Furthermore, heavy smokers demonstrated decreased nodal global efficiency mainly in brain regions within the default mode network, whereas increased nodal local efficiency predominated in the visual-related regions. In addition, heavy smokers exhibited an association between the altered network metrics and the duration of cigarette use or the severity of nicotine dependence. Our results suggest that heavy smokers may have less efficient network architecture in the brain, and chronic cigarette smoking is associated with disruptions in the topological organization of brain networks. Our findings may further the understanding of the effects of chronic cigarette smoking on the brain and the pathophysiological mechanisms underlying nicotine dependence.

Cardiovascular risk factors and cognitive decline in older people with type 2 diabetes

AIMS/HYPOTHESIS

The aim of this work was to assess the role of well-established cardiovascular risk factors in the late-life cognitive decline of patients with type 2 diabetes.

METHODS

Data from 831 participants (aged 60-75 years) attending the 4 year follow-up of the Edinburgh Type 2 Diabetes Study (ET2DS) were used. Smoking history (pack-years), BP, HbA1c, plasma glucose and cholesterol were determined at baseline clinics (single time measurements) and/or from serial data recorded on a clinical management database from diagnosis until recruitment ('historical' data). Principal component analysis derived a factor, g, of general ability from seven cognitive tests. Linear regression models of follow-up g were adjusted for baseline g to represent 4 year cognitive change. 'Accelerated late-life cognitive decline' was defined as scoring in the lowest tertile of '4 year cognitive change' regression scores. Analyses controlled for age and sex.

RESULTS

A baseline history of moderate/heavy smoking (≥ 10 pack-years) and a 1% increased historical HbA1c (equivalent to an increase by 11 mmol/mol) predicted a 64% (OR 1.64; 95% CI 1.14, 2.34; p = 0.007) and 21% (OR 1.21; 95% CI 1.00, 1.45; p = 0.046) increased risk of accelerated cognitive decline, respectively. When treated as continuous measures, higher pack-years, historical HbA1c and historical BP emerged as significant independent predictors of 4 year decline in g (standardised β range -0.07 to -0.14; all p ≤ 0.05).

CONCLUSIONS/INTERPRETATION

Increased smoking and poorer glycaemic control (with relatively weaker findings for BP) during the life-course were independently associated with accelerated late-life cognitive decline. Where possible, evaluation is warranted of these risk factors as targets for intervention to reduce the burden of cognitive impairment in diabetes.

Smoking and cognitive impairment among older persons in Malaysia

INTRODUCTION

Previous studies have shown conflicting results on the association between smoking and cognitive function. This study aims to examine the relationship of smoking with cognitive function.

METHODOLOGY

Data for the study, consisting of 2553 older adults aged 60 years and older, were drawn from a nationwide household survey entitled "Determinants of Wellness among Older Malaysians: A Health Promotion Perspective" conducted in 2010.

RESULTS

Current smokers had lower rates of cognitive impairment compared to never smokers (17.4% vs 25.9%), while cognitive function in former or ex-smokers was almost similar to that of the never smokers. Findings from multiple logistic regression analysis showed that current smokers were 37% less likely to be cognitively impaired, compared to the never smokers (odds ratio [OR] = .63; 95% confidence interval [CI]: .46-.86) while controlling for potential confounders. No difference in cognitive function was observed between former smokers and never smokers (OR = .94; 95% CI: .71-1.25).

CONCLUSION

Although the findings indicated a negative association between cigarette smoking and cognitive impairment, we are unable to conclude whether this relationship is causal or affected by other unmeasured confounding factors, especially survival bias.

Gender differences in the effect of tobacco use on brain phosphocreatine levels in methamphetamine-dependent subjects

BACKGROUND

A high prevalence of tobacco smoking has been observed in methamphetamine users, but there have been no in vivo brain neurochemistry studies addressing gender effects of tobacco smoking in methamphetamine users. Methamphetamine addiction is associated with increased risk of depression and anxiety in females. There is increasing evidence that selective analogues of nicotine, a principal active component of tobacco smoking, may ease depression and improve cognitive performance in animals and humans.

OBJECTIVES

To investigate the effects of tobacco smoking and gender on brain phosphocreatine (PCr) levels, a marker of brain energy metabolism reported to be reduced in methamphetamine-dependent subjects.

METHODS

Thirty female and 27 male methamphetamine-dependent subjects were evaluated with phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) to measure PCr levels within the pregenual anterior cingulate, which has been implicated in methamphetamine neurotoxicity.

RESULTS

Analysis of covariance revealed that there were statistically significant slope (PCr versus lifetime amount of tobacco smoking) differences between female and male methamphetamine-dependent subjects (p = 0.03). In females, there was also a statistically significant interaction between lifetime amounts of tobacco smoking and methamphetamine in regard to PCr levels (p = 0.01), which suggests that tobacco smoking may have a more significant positive impact on brain PCr levels in heavy, as opposed to light to moderate, methamphetamine-dependent females.

CONCLUSION

These results indicate that tobacco smoking has gender-specific effects in terms of increased anterior cingulate high energy PCr levels in methamphetamine-dependent subjects. Cigarette smoking in methamphetamine-dependent women, particularly those with heavy methamphetamine use, may have a potentially protective effect upon neuronal metabolism.

Smoking history, and not depression, is related to deficits in detection of happy and sad faces

INTRODUCTION

Previous research has demonstrated that chronic cigarette smoking and major depressive disorder (MDD) are each associated with cognitive decrements. Further, these conditions co-occur commonly, though mechanisms in the comorbid condition are poorly understood. There may be distinct, additive, or overlapping factors underlying comorbid cigarette smoking and MDD. The present study investigated the impact of smoking and MDD on executive function and emotion processing.

METHODS

Participants (N=198) were grouped by diagnostic category (MDD and healthy controls, HC) and smoking status (ever-smokers, ES and never-smokers, NS). Participants completed the Facial Emotion Perception Test (FEPT), a measure of emotional processing, and the parametric Go/No-go task (PGNG), a measure of executive function.

RESULTS

FEPT performance was analyzed using ANCOVA with accuracy and reaction time as separate dependent variables. Repeated measures MANCOVA was conducted for PGNG with performance measure and task level as dependent variables. Analyses for each task included diagnostic and smoking group as independent variables, and gender was controlled for. Results for FEPT reveal that lower overall accuracy was found for ES relative to NS, though MDD did not differ from HC. Post-hoc analyses revealed that ES were poorer at identifying happy and sad, but not fearful or angry, faces. For PGNG, poorer performance was observed in MDD relative to HC in response time to Go targets, but there were no differences for ES and NS. Interaction of diagnosis and smoking group was not observed for performance on either task.

CONCLUSIONS

The results of this study provide preliminary evidence for distinctive cognitive decrements in smokers and individuals with depression.

Smoking, MATRICS consensus cognitive battery and P50 sensory gating in a Han Chinese population

BACKGROUND

The effects of smoking on cognitive performance have long been studied, with mixed results. P50 sensory gating has been used as endophenotype for studying nicotinic systems genetics, and P50 gating deficits have been reported to be a sensitive biomarker for cognitive impairment in schizophrenia. This study examined the inter-relationship between P50 suppression, cognitive function, and smoking in a healthy Han Chinese population, which has not been reported before.

METHODS

We recruited 82 healthy male subjects, including 48 smokers and 34 non-smokers who were matched for age and education. The authors measured P50 sensory gating and administered the Chinese-language version of the MATRICS consensus cognitive battery (MCCB) and Stroop tests.

RESULTS

The results showed that the smokers scored lower than nonsmokers on the MCCB brief visuospatial memory test (BVMT) index and the STROOP test. Furthermore, the MCCB total score was negatively associated with number of cigarettes smoked per day in the smoker group. However, P50 sensory gating was not associated with either smoking status or any cognitive performance.

CONCLUSIONS

Our results show that smoking is associated with cognitive impairment, but not with P50 sensory gating.

Dual role of nicotine in addiction and cognition: a review of neuroimaging studies in humans

Substantial evidence demonstrates both nicotine's addiction liability and its cognition-enhancing effects. However, the neurobiological mechanisms underlying nicotine's impact on brain function and behavior remain incompletely understood. Elucidation of these mechanisms is of high clinical importance and may lead to improved therapeutics for smoking cessation as well as for a number of cognitive disorders such as schizophrenia. Neuroimaging techniques such as positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI), which make it possible to study the actions of nicotine in the human brain in vivo, play an increasingly important role in identifying these dual mechanisms of action. In this review, we summarize the current state of knowledge and discuss outstanding questions and future directions in human neuroimaging research on nicotine and tobacco. This research spans from receptor-level PET and SPECT studies demonstrating nicotine occupancy at nicotinic acetylcholine receptors (nAChRs) and upregulation of nAChRs induced by chronic smoking; through nicotine's interactions with the mesocorticolimbic dopamine system believed to mediate nicotine's reinforcing effects leading to dependence; to functional activity and connectivity fMRI studies documenting nicotine's complex behavioral and cognitive effects manifest by its actions on large-scale brain networks engaged both during task performance and at rest. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.

Life-course socio-economic disadvantage and late-life cognitive functioning in Taiwan: results from a national cohort study

BACKGROUND

Declines in late-life cognitive functioning differ greatly between socio-economic status (SES) groups, but little is known about whether these effects are related to child and adult SES versus SES effects that accumulate over the individual's life course.

METHODS

An 18-year longitudinal national sample of older adults from Taiwan (n=2944) was used to estimate the effect of socio-economic disadvantage over the individual's life course on cognitive functioning during late life. Cognitive functioning was assessed using the brief Short Portable Mental Status Questionnaire scale. Life-course socio-economic disadvantage, as accrued during childhood and adulthood, included measures of paternal education and occupation and participant's education and occupation.

RESULTS

Multivariate analyses using various mixed-effects models showed that the effects of childhood SES could be largely explained by adult SES and that disadvantageous SES in adulthood further exacerbated declines in late-life cognitive functioning (β=-0.02; p<0.001), even controlling for aging, practice and other covariates. Possible factors that are associated with life-course socio-economic disadvantage and late-life cognitive decline included household income and perception of economic strain.

CONCLUSIONS

The results suggest a critical role for life-course socio-economic disadvantage in late-life cognitive decline and that this may be manifested via the inequitable distribution of socio-economic resources over the individual's life course.

Trajectories of cigarette smoking from adolescence to adulthood as predictors of unemployment status

INTRODUCTION

This longitudinal study examined the association between trajectories of cigarette smoking and unemployment across a 29-year time period from mean age 14 to mean age 43.

METHODS

Participants came from a community-based random sample of residents in 2 upstate New York counties. Data were collected at 7 timepoints.

RESULTS

Using growth mixture modeling, 5 trajectory groups of cigarette smokers were identified. The trajectory groups were as follows: heavy/continuous smokers, occasional smokers, late-starting smokers, quitters/decreasers, and nonsmokers. Multivariate logistic regression analysis was used to study the relationship between the participant's trajectory group membership and unemployment in the fifth decade of life. The association was determined with controls for age, gender, current cigarette use, current alcohol use, current marijuana use, physical diseases, occupation, educational level, past unemployment experience, socioeconomic status measures of family of origin, depressive mood, and self-control from adolescence through the early 40s. The findings indicate that patterns of adolescent and young adult cigarette smoking have implications for later unemployment. Overall, the results showed that people who fell into the categories of heavy/continuous smokers (adjusted odds ratio [AOR] = 3.84) and occasional smokers (AOR = 4.03) were more likely to be unemployed at mean age 43 when compared with nonsmokers. There was no significant difference between the quitters/decreasers and the nonsmokers with respect to unemployment.

CONCLUSIONS

Intervention programs designed to deal with unemployment should consider focusing on heavy/continuous and occasional cigarette smokers as risk factors for unemployment.

Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis

Background

Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer’s disease (AD) is the most frequent cause of dementia, increasing in prevalence from <1% below the age of 60 years to >40% above 85 years of age.

Methods

We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias.

Results

In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ~38.9% for caffeine to ~89% for physical activity. Education also had a significantly higher propensity for “a positive finding” compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found.

Conclusions

Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

Vorinostat positively regulates synaptic plasticity genes expression and spine density in HIV infected neurons: role of nicotine in progression of HIV-associated neurocognitive disorder

Background

HIV-associated neurocognitive disorder (HAND) is characterized by development of cognitive, behavioral and motor abnormalities, and occurs in approximately 50% of HIV infected individuals. In the United States, the prevalence of cigarette smoking ranges from 35-70% in HIV-infected individuals compared to 20% in general population. Cognitive impairment in heavy cigarette smokers has been well reported. However, the synergistic effects of nicotine and HIV infection and the underlying mechanisms in the development of HAND are unknown.

Results

In this study, we explored the role of nicotine in the progression of HAND using SK-N-MC, a neuronal cell line. SK-N-MC cells were infected with HIV-1 in the presence or absence of nicotine for 7 days. We observed significant increase in HIV infectivity in SK-N-MC treated with nicotine compared to untreated HIV-infected neuronal cells. HIV and nicotine synergize to significantly dysregulate the expression of synaptic plasticity genes and spine density; with a concomitant increase of HDAC2 levels in SK-N-MC cells. In addition, inhibition of HDAC2 up-regulation with the use of vorinostat resulted in HIV latency breakdown and recovery of synaptic plasticity genes expression and spine density in nicotine/HIV alone and in co-treated SK-N-MC cells. Furthermore, increased eIF2 alpha phosphorylation, which negatively regulates eukaryotic translational process, was observed in HIV alone and in co-treatment with nicotine compared to untreated control and nicotine alone treated SK-N-MC cells.

Conclusions

These results suggest that nicotine and HIV synergize to negatively regulate the synaptic plasticity gene expression and spine density and this may contribute to the increased risk of HAND in HIV infected smokers. Apart from disrupting latency, vorinostat may be a useful therapeutic to inhibit the negative regulatory effects on synaptic plasticity in HIV infected nicotine abusers.

Disparities in current cigarette smoking prevalence by type of disability, 2009-2011

OBJECTIVES

Smoking, the leading cause of disease and death in the United States, has been linked to a number of health conditions including cancer and cardiovascular disease. While people with a disability have been shown to be more likely to report smoking, little is known about the prevalence of smoking by type of disability, particularly for adults younger than 50 years of age.

METHODS

We used data from the 2009-2011 National Health Interview Survey to estimate the prevalence of smoking by type of disability and to examine the association of functional disability type and smoking among adults aged 18-49 years.

RESULTS

Adults with a disability were more likely than adults without a disability to be current smokers (38.8% vs. 20.7%, p<0.001). Among adults with disabilities, the prevalence of smoking ranged from 32.4% (self-care difficulty) to 43.8% (cognitive limitation). When controlling for sociodemographic characteristics, having a disability was associated with statistically significantly higher odds of current smoking (adjusted odds ratio = 1.57, 95% confidence interval 1.40, 1.77).

CONCLUSIONS

The prevalence of current smoking for adults was higher for every functional disability type than for adults without a disability. By understanding the association between smoking and disability type among adults younger than 50 years of age, resources for cessation services can be better targeted during the ages when increased time for health improvement can occur.

[Factors Associated with Cognitive Decline in a Population Less than 65 Years Old. A Systematic Review]

INTRODUCTION

Cognitive decline could begin 20 years before the diagnosis of dementia. Besides age, several factors related to medical, socioeconomic, and behavioral and genetic condition may be associated with cognitive decline. The aim of this systematic review was to summarize evidence on the risk and protective factors for cognitive decline in people under 65 years old.

METHODS

A systematic review was conducted using a search strategy in MEDLINE and Embase, including longitudinal studies to analyze the effect of protective or risk factors on cognitive decline in a population under 65 years old.

RESULTS

A total of 22 studies were included in this review. Factors such as diabetes, hyperinsulinemia, overweight or obesity, metabolic syndrome, education, physical activity, cognitive stimulation, marital status and diet, could be related to cognitive decline before 65 years of age.

CONCLUSIONS

Cardiovascular risk factors and lifestyle conditions may be associated with cognitive decline before 65 years of age. However, the quality of the evidence was low.

Adolescent self-organization predicts midlife memory in a prospective birth cohort study

Childhood and adolescent mental health have a lasting impact on adult life chances, with strong implications for subsequent health, including cognitive aging. Using the British 1946 birth cohort, the authors tested associations between adolescent conduct problems, emotional problems and aspects of self-organization, and verbal memory at 43 years and rate of decline in verbal memory from 43 to 60-64 years. After controlling for childhood intelligence, adolescent self-organization was positively associated with verbal memory at 43 years, mainly through educational attainment, although not with rate of memory decline. Associations between adolescent conduct and emotional problems and future memory were of negligible magnitude. It has been suggested that interventions to improve self-organization may save a wide range of societal costs; this study also suggests that this might also benefit cognitive function in later life.

Neurocognitive impairments in non-deprived smokers--results from a population-based multi-center study on smoking-related behavior

The aim of the present study was to examine neurocognitive function associated with chronic nicotine use. A total of 2163 healthy participants (1002 smokers, 1161 never-smoking controls) participated in a population-based case-control design. The main outcome measures were six cognitive domain factors derived from a neuropsychological test battery. In smokers, the battery was administered after controlled smoking of one cigarette. Analyses included age, sex and education as covariates. Results demonstrated small, but significant deficits in smokers for visual attention (P<0.001) and cognitive impulsivity (P<0.006), while verbal episodic memory, verbal fluency, verbal working memory, and Stroop-interference did not differ between groups. These attention/impulsivity deficits were also present in smokers with only a low amount of cigarette consumption. Lifetime nicotine use (pack-years) was not correlated with cognition in smokers. In conclusion, this study confirmed subtle and specific cognitive deficits in non-deprived smokers. The independence of these deficits from consumption intensity may argue for an a priori deficit of some cognitive abilities in smokers. These specific deficits may constitute intermediate phenotypes for genetic research on nicotine use.

Smoking exacerbates amyloid pathology in a mouse model of Alzheimer's disease

Several epidemiological studies have shown that cigarette smoking might alter the incidence of Alzheimer's disease. However, inconsistent results have been reported regarding the risk of Alzheimer's disease among smokers. Previous studies in experimental animal models have reported that administration of some cigarette components (for example, nicotine) alters amyloid-β aggregation, providing a possible link. However, extrapolation of these findings towards the in vivo scenario is not straightforward as smoke inhalation involves a number of other components. Here, we analysed the effect of smoking under more relevant conditions. We exposed transgenic mouse models of Alzheimer's disease to cigarette smoke and analysed the neuropathological alterations in comparison with animals not subjected to smoke inhalation. Our results showed that smoking increases the severity of some abnormalities typical of Alzheimer's disease, including amyloidogenesis, neuroinflammation and tau phosphorylation. Our findings suggest that cigarette smoking may increase Alzheimer's disease onset and exacerbate its features and thus, may constitute an important environmental risk factor for Alzheimer's disease.

Cardiovascular risk factors and cognitive decline in adults aged 50 and over: a population-based cohort study

OBJECTIVES

the objective of the present study was to explore the association between cardiovascular risk and cognitive decline in adults aged 50 and over.

METHODS

participants were older adults who participated in the English Longitudinal Study of Ageing. Outcome measures included standardised z-scores for global cognition, memory and executive functioning. Associations between cardiovascular risk factors and 10-year Framingham risk scores with cognitive outcomes at 4-year and 8-year follow-ups were estimated.

RESULTS

the mean age of participants (n = 8,780) at 2004-05 survey was 66.93 and 55% were females. Participants in the highest quartile of Framingham stroke risk score (FSR) had lower global cognition (b = -0.73,CI: -1.37, -0.10), memory (b = -0.56, CI: -0.99, -0.12) and executive (b = -0.37, CI: -0.74, -0.01) scores at 4-year follow-up compared with those in the lower quartile. Systolic blood pressure ≥160 mmHg at 1998-2001 survey was associated with lower global cognitive (b = -1.26, CI: -2.52, -0.01) and specific memory (b = -1.16, CI: -1.94, -0.37) scores at 8-year follow-up. Smoking was consistently associated with lower performance on all three cognitive outcomes.

CONCLUSION

elevated cardiovascular risk may be associated with accelerated decline in cognitive functioning in the elderly. Future intervention studies may be better focused on overall risk rather than individual risk factor levels.

How cigarette smoking may increase the risk of anxiety symptoms and anxiety disorders: a critical review of biological pathways

Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis.

Smoking-related prospective memory deficits observed on naturalistic everyday memory task

OBJECTIVE

This study assessed self-reported and objective prospective memory (PM) processes in smokers and a never-smoked comparison group. If persistent smoking does impair PM, then one would expect smokers recall being lower on a study that requires them to remember everyday activities when compared with a never-smoked group.

METHOD

An existing-groups design was used to compare a group of smokers with a never-smoked group on the self-report Prospective Memory Questionnaire (PMQ) and the Prospective Remembering Video Procedure (PRVP) measuring objective PM. An example of the location-action combination from the PRVP is 'At Thornton's shop' (location), 'Buy a bag of sweets' (action). Participants who reported using an illegal substance (e.g. ecstasy, cannabis), who drank excessively or were 'binge drinkers', or who reported suffering from a clinical condition, such as depression, were excluded from the study. Age, weekly 'safe levels' alcohol use, and strategy use were also measured and controlled for in the study. Each person was tested individually in a quiet laboratory setting on a university campus.

RESULTS

After controlling for variations in age, weekly alcohol use, and strategy use, smokers recalled significantly fewer location-action combinations on the PRVP when compared with a never-smoked group, with no between-group differences on self-reported PM as measured by the PMQ.

CONCLUSIONS

The findings suggest objective PM deficits are associated with persistent smoking - a relatively unexplored area of research. This cannot be attributed to other drug use, mood, or strategy use. The findings also suggest smokers lack self-awareness of such PM deficits. This study extends the area by utilising a more naturalistic object measure of PM and incorporating strict controls into the study.

The effects of cigarette smoking on learning and memory performance among people living with HIV/AIDS

The purpose of this study was to examine the effects of smoking (past and current) on multiple domains of cognitive functioning in a sample of people living with HIV/AIDS (PLWHA). We hypothesized that among PLWHA, current smokers would demonstrate poorer cognitive functioning when compared to non-smokers, specifically in the cognitive domains of auditory-verbal learning and memory, visuospatial memory, overall cognitive efficiency, executive skills, processing speed, and working memory. Results suggest that in patients being treated for HIV infection, current smoking is negatively associated with learning, memory, and global cognitive functioning. There was also some evidence that cognitive deficits in learning associated with smoking were more pronounced among men compared to women. However, the cause of these effects is not at all clear. In multivariate models, the differences associated with smoking were non-significant when adjusting for education and hepatitis C virus infection. Therefore, smoking may simply reflect a general tendency to more widespread deficits and comorbidities rather than directly impacting cognitive function. Future studies should attempt to examine a priori cognitive factors which contribute to smoking debut and other associated risk factors in order to understand why smoking may be a marker for other risk factors and may ultimately influence neurocognitive functioning critical to daily activities and adherence.

Executive functions in adult offspring of alcohol-dependent probands: toward a cognitive endophenotype?

BACKGROUND

Executive function (EF) impairment in alcohol dependence (AD) has been related to the toxic effects of alcohol on frontal lobes. However, this impairment could be partially present before the onset of the disease and might constitute a vulnerability factor. Although a considerable body of research has investigated executive functioning among AD patients, much less attention has been directed toward high-risk individuals. Most studies were carried out among children or adolescents, and very few were conducted in adults. The aim of this study was to examine EF in a group of adult offspring of AD individuals.

METHODS

One hundred and fifty-five nonalcoholic adults with (family history positive [FHP]) or without (family history negative [FHN]) family history of AD were included in the study. All participants were screened for past and current psychiatric diagnoses, and alcohol, tobacco, and other substance use. They were compared on self-rated impulsiveness using the Barratt Impulsiveness Scale-11 (BIS-11) and EF using a neuropsychological test battery.

RESULTS

Group comparison revealed that FHP participants had significantly higher BIS-11 scores than the FHN participants, while neuropsychological examination revealed lower EF scores for FHP participants. Hierarchical regression analysis revealed that the number of AD family members was a predictor of EF results, whereas impulsiveness was not.

CONCLUSIONS

Nonalcoholic adult offspring of AD individuals showed increased impulsiveness and decreased EF, suggesting weakness of 2 distinct neurobehavioral decision systems. Findings support evidence that EF weaknesses may qualify as a suitable endophenotype candidate for AD.

Chronic smoking and brain gray matter changes: evidence from meta-analysis of voxel-based morphometry studies

Structural neuroimaging studies on chronic smokers using voxel-based morphometry (VBM) had provided cumulative evidence of gray matter (GM) changes relative to nonsmokers. However, not all the studies reported entirely consistent findings. Here, we aimed at identifying consistent GM anomalies in chronic smokers by performing a meta-analysis, and a systematic search of VBM studies on chronic smokers and nonsmokers published in PubMed and Embase database from 2000 to April 2012. Meta-analysis was performed using a newly improved voxel-based meta-analytic tool, namely effect size signed differential mapping, to quantitatively explore the GM abnormalities between chronic smokers and nonsmokers. A total of 7 eligible VBM studies involving 213 chronic smokers and 205 nonsmokers met the inclusion criteria. A considerable regional GM volume decrease was detected in the anterior cingulate cortex (ACC) (BA 24) extending to BA32 in chronic smokers. The findings remain largely unchanged in the entire brain jackknife sensitivity analyses. The results of the present meta-analysis provide evidence of GM changes in ACC in chronic smokers which may be an important potential therapeutic neuro-target for nicotine dependence.

Short- and long-term consequences of nicotine exposure during adolescence for prefrontal cortex neuronal network function

More than 70% of adolescents report to have smoked a cigarette at least once. At the adolescent stage the brain has not completed its maturation. The prefrontal cortex (PFC), the brain area responsible for executive functions and attention performance, is one of the last brain areas to mature and is still developing during adolescence. Smoking during adolescence increases the risk of developing psychiatric disorders and cognitive impairment in later life. In addition, adolescent smokers suffer from attention deficits, which aggravate with the years of smoking. Recent studies in rodents reveal the molecular changes induced by adolescent nicotine exposure that alter the functioning of synapses in the PFC and that underlie the lasting effects on cognitive function. Here we provide an overview of these recent findings.

Impact of smoking on cognitive decline in early old age: the Whitehall II cohort study

CONTEXT

Smoking is a possible risk factor for dementia, although its impact may have been underestimated in elderly populations because of the shorter life span of smokers.

OBJECTIVE

To examine the association between smoking history and cognitive decline in the transition from midlife to old age.

DESIGN

Cohort study.

SETTING

The Whitehall II study. The first cognitive assessment was in 1997 to 1999, repeated over 2002 to 2004 and 2007 to 2009.

PARTICIPANTS

Data are from 5099 men and 2137 women in the Whitehall II study, mean age 56 years (range, 44-69 years) at the first cognitive assessment.

MAIN OUTCOME MEASURES

The cognitive test battery was composed of tests of memory, vocabulary, executive function (composed of 1 reasoning and 2 fluency tests), and a global cognitive score summarizing performance across all 5 tests. Smoking status was assessed over the entire study period. Linear mixed models were used to assess the association between smoking history and 10-year cognitive decline, expressed as z scores.

RESULTS

In men, 10-year cognitive decline in all tests except vocabulary among never smokers ranged from a quarter to a third of the baseline standard deviation. Faster cognitive decline was observed among current smokers compared with never smokers in men (mean difference in 10-year decline in global cognition=-0.09 [95% CI, -0.15 to -0.03] and executive function=-0.11 [95% CI, -0.17 to -0.05]). Recent ex-smokers had greater decline in executive function (-0.08 [95% CI, -0.14 to -0.02]), while the decline in long-term ex-smokers was similar to that among never smokers. In analyses that additionally took dropout and death into account, these differences were 1.2 to 1.5 times larger. In women, cognitive decline did not vary as a function of smoking status.

CONCLUSIONS

Compared with never smokers, middle-aged male smokers experienced faster cognitive decline in global cognition and executive function. In ex-smokers with at least a 10-year cessation, there were no adverse effects on cognitive decline.

The role of lifestyle behaviors on 20-year cognitive decline

This study examined the association between smoking, physical activity and dietary choice at 36 and 43 years, and change in these lifestyle behaviors between these ages, and decline in verbal memory and visual search speed between 43 and 60-64 years in 1018 participants from MRC National Survey of Health and Development (NSHD, the British 1946 birth cohort). ANCOVA models were adjusted for sex, social class of origin, childhood cognition, educational attainment, adult social class, and depression; then the lifestyle behaviors were additionally mutually adjusted. Results showed that healthy dietary choice and physical activity were associated, respectively, with slower memory and visual search speed decline over 20 years, with evidence that increasing physical activity was important. Adopting positive health behaviors from early midlife may be beneficial in reducing the rate of cognitive decline and ultimately reducing the risk of dementia.

Nicotine exposure during adolescence alters the rules for prefrontal cortical synaptic plasticity during adulthood

The majority of adolescents report to have smoked a cigarette at least once. Adolescence is a critical period of brain development during which maturation of areas involved in cognitive functioning, such as the medial prefrontal cortex (mPFC), is still ongoing. Tobacco smoking during this age may compromise the normal course of prefrontal development and lead to cognitive impairments in later life. In addition, adolescent smokers suffer from attention deficits, which progress with the years of smoking. Recent studies in rodents reveal the molecular changes induced by adolescent nicotine exposure that alter the functioning of synapses in the PFC and underlie the lasting effects on cognitive function. In particular, the expression and function of metabotropic glutamate receptors (mGluRs) are changed and this has an impact on short- and long-term plasticity of glutamatergic synapses in the PFC and ultimately on the attention performance. Here, we review and discuss these recent findings.

Smoking, childhood IQ, and cognitive function in old age

OBJECTIVES

To examine the association between smoking history and cognitive function in old age, and whether it remains after controlling for childhood cognitive ability (IQ) and adult socioeconomic status (SES).

METHODS

In the Lothian Birth Cohort 1936 Study, 1080 men and women, who previously participated in a nationwide IQ-type test in childhood, were followed up at age 70. The associations between smoking history and age 70 IQ, general cognitive ability (g), processing speed, memory, and verbal ability were assessed.

RESULTS

Lower childhood IQ was associated with a higher risk of becoming a smoker and continuing to smoke in late life, and with reduced lung function (FEV1) in late life. Current smokers scored significantly lower than ex-smokers and never smokers on tests of age 70 IQ, general cognitive ability, and processing speed, but not memory or verbal ability. After controlling for childhood IQ and SES, current smoking at age 70 (but not pack years of smoking) was associated with impairments in general cognitive ability and processing speed.

CONCLUSION

Smoking in old age makes a small, independent contribution to cognitive performance in old age.

Cigarette smoking might impair memory and sleep quality

Although nicotine can enhance some cognitive functions, cigarette smoking may impair memory and sleep quality. Our aim was to investigate the impact of cigarette smoking on memory and sleep quality in healthy smokers. Sixty-eight healthy participants (34 smokers and 34 controls) completed the Wechsler Memory Scale-Revised and a Chinese version of the Pittsburgh Sleep Quality Index. The Wilcoxon signed ranks test was performed, and Hochberg's Sharpened Bonferroni correction was applied for multiple comparisons. The results show that current smokers had a worse visual memory compared to nonsmokers. There was no significant correlation between the index of Wechsler Memory Scale-Revised and Fagerström test for nicotine dependence. Moreover, smokers had poorer sleep quality. Cigarette smoking might impair memory and adversely influence sleep quality.

Developmental effects of acute, chronic, and withdrawal from chronic nicotine on fear conditioning

Pre-adolescence and adolescence are developmental periods associated with increased vulnerability for tobacco addiction, and exposure to tobacco during these periods may lead to long-lasting changes in behavioral and neuronal plasticity. The present study examined the short- and long-term effects of nicotine and nicotine withdrawal on fear conditioning in pre-adolescent, adolescent, and adult mice, and potential underlying substrates that may mediate the developmental effects of nicotine, such as changes in nicotinic acetylcholine receptor (nAChR) binding, CREB expression, and nicotine metabolism. Age-related differences existed in sensitivity to the effects of acute nicotine, chronic nicotine and nicotine withdrawal on contextual fear conditioning (no changes in cued fear conditioning were seen); younger mice were more sensitive to the acute effects and less sensitive to the effects of nicotine withdrawal 24 h post treatment cessation. Developmental differences in nAChR binding were associated with the effects of nicotine withdrawal on contextual learning. Developmental differences in nicotine metabolism and CREB expression were also observed, but were not related to the effects of nicotine withdrawal on contextual learning 24 h post treatment. Chronic nicotine exposure during pre-adolescence or adolescence, however, produced long-lasting impairments in contextual learning that were observed during adulthood, whereas adult chronic nicotine exposure did not. These developmental effects could be related to changes in CREB. Overall, there is a developmental shift in the effects of nicotine on hippocampus-dependent learning and developmental exposure to nicotine results in adult cognitive deficits; these changes in cognition may play an important role in the development and maintenance of nicotine addiction.

A comprehensive assessment of neurocognition in middle-aged chronic cigarette smokers

BACKGROUND

The majority of studies investigating the neurocognitive consequences of chronic smoking have been conducted with adults 60 years and older. Therefore, the scope of neurocognitive dysfunction associated with chronic cigarette smoking in middle age (i.e., 30-60 age range) has not been fully delineated.

METHODS

Twenty-seven (44±9 years of age; 4 females) non-smoking and 30 smoking (49±8 years of age; 4 females) participants completed a comprehensive neurocognitive battery and measures of fine motor dexterity and postural stability. All participants were free of biomedical or psychiatric conditions that may have influenced neurocognitive and motor function.

RESULTS

Smokers performed significantly worse than non-smokers on the following domains: auditory-verbal and visuospatial learning, visuospatial memory, cognitive efficiency, executive skills, general intelligence, processing speed, fine motor dexterity and postural stability. The differences between smokers and non-smokers evidenced moderate to strong effect sizes and were not mediated by age, education, vocational level, estimated verbal intelligence or alcohol consumption. In smokers, a greater number of lifetime years of smoking was related to poorer performance on measures of cognitive efficiency, processing speed and visuospatial skills.

CONCLUSIONS

Results from this middle-aged cohort replicated previous research and provides novel findings indicating that chronic smoking was associated with inferior performance on measures of general intelligence, visuospatial learning and memory and fine motor dexterity. Research that relates measures of neurobiological function/integrity to neurocognition is needed to better understand the mechanisms contributing to the poorer performance across multiple domains demonstrated by smokers.

Accounting for bias due to selective attrition: the example of smoking and cognitive decline

BACKGROUND

Selective attrition may introduce bias into analyses of the determinants of cognitive decline. This is a concern especially for risk factors, such as smoking, that strongly influence mortality and dropout. Using inverse-probability-of-attrition weights, we examined the influence of selective attrition on the estimated association of current smoking (vs. never smoking) with cognitive decline.

METHODS

Chicago Health and Aging Project participants (n = 3713), aged 65-109 years, who were current smokers or never- smokers, underwent cognitive assessments up to 5 times at 3-year interval. We used pooled logistic regression to fit predictive models of attrition due to death or study dropout across the follow-up waves. With these models, we computed inverse-probability-of-attrition weights for each observation. We fit unweighted and weighted, multivariable-adjusted generalized-estimating-equation models, contrasting rates of change in cognitive scores in current versus never-smokers. Estimates are expressed as rates of change in z score per decade.

RESULTS

During the 12 years of follow-up, smokers had higher mortality than never-smokers (hazard ratio = 1.93 [95% confidence interval = 1.67 to 2.23]). Higher previous cognitive score was associated with increased likelihood of survival and continued participation. In unweighted analyses, current smokers' cognitive scores declined 0.11 standard units per decade more rapidly than never-smokers' (95% CI = -0.20 to -0.02). Weighting to account for attrition yielded estimates that were 56% to 86% larger, with smokers' estimated 10-year rate of decline up to 0.20 units faster than never-smokers' (95% CI = -0.36 to -0.04).

CONCLUSIONS

Estimates of smoking's effects on cognitive decline may be underestimated due to differential attrition. Analyses that weight for the inverse probability of attrition help compensate for this attrition.

Chronic Cigarette Smoking Alters Circulating Sex Hormones and Neuroactive Steroids in Premenopausal Women

Chronic smoking alters the circulating levels of sex hormones and possibly also the neuroactive steroids. However, the data available is limited. Therefore, a broad spectrum of free and conjugated steroids and related substances was quantified by GC-MS and RIA in premenopausal smokers and in age-matched (38.9±7.3 years of age) non-smokers in the follicular (FP) and luteal phases (LP) of menstrual cycle (10 non-smokers and 10 smokers, in the FP, and 10 non-smokers and 8 smokers in the LP). Smokers in both phases of the menstrual cycle showed higher levels of conjugated 17-hydroxypregnenolone, 5α-dihydroprogesterone, conjugated isopregnanolone, conjugated 5α-pregnane-3β,20α-diol, conjugated androstenediol, androstenedione, testosterone, free testosterone, conjugated 5α-androstane-3α/β,17β-diols, and higher free testosterone index. In the FP, the smokers exhibited higher levels of conjugated pregnenolone, progesterone, conjugated pregnanolone, lutropin, and a higher lutropin/follitropin ratio, but lower levels of cortisol, allopregnanolone, and pregnanolone. In the LP, the smokers exhibited higher levels of free and conjugated 20α-dihydropregnenolone, free and conjugated dehydroepiandrosterone, free androstenediol, 5α-dihydro-testosterone, free and conjugated androsterone, free and conjugated epiandrosterone, free and conjugated etiocholanolone, 7α/β-hydroxy-dehydroepiandrosterone isomers, and follitropin but lower levels of estradiol and sex hormone binding globulin (SHBG) and lower values of the lutropin/follitropin ratio. In conclusion, chronic cigarette smoking augments serum androgens and their 5α/β-reduced metabolites (including GABAergic substances) but suppresses the levels of estradiol in the LP and SHBG and may induce hyperandrogenism in female smokers. The female smokers had pronouncedly increased serum progestogens but paradoxically suppressed levels of their GABA-ergic metabolites. Further investigation is needed concerning these effects.

Smoking-related prospective memory deficits in a real-world task

BACKGROUND

Smokers, previous smokers and a never smoked group were compared on self-reported and real world prospective memory (PM - the cognitive ability of remembering to carry out particular actions at some future point in time).

METHODS

Twenty-seven current smokers, 24 people who had never smoked and 18 previous smokers were compared using an existing groups design. Scores on the long and short term PM subscales of the Prospective and Retrospective Memory Questionnaire (PRMQ) and scores on a Real World Prospective Memory Task (RWPMT) constituted the dependent measures. Smoking and other drug use were assessed by a Recreational Drug Use Questionnaire. The Hospital Anxiety and Depression Scale gauged levels of anxiety and depression. The National Adult Reading Test measured IQ, and retrospective memory was measured using the PRMQ. Gender, age, anxiety and depression, IQ, alcohol use and the retrospective memory scores, were measured as covariates and controlled for in the analysis.

RESULTS

A series of univariate ANCOVAs were applied to the main PM data across the three groups, controlling for variations in age, gender, mood, IQ, alcohol use and retrospective memory scores. These revealed no significant between-group differences on self-reported PM; however smokers recalled significantly fewer action-location combinations than the never smoked and previous smoker groups on the objective RWPMT.

CONCLUSIONS

Existing smokers showed reduced performance on RWPMT when compared to the never smoked group and previous smokers. Real-world PM impairments should be added to a growing list of neuropsychological sequelae associated with persistent smoking.

Smoking differences between employees in faculties of the University of Tartu, Estonia, and changes during the country's transition

Background

A previous study found marked differences in smoking between employees in various university faculties in Tartu, Estonia, soon after the disruption of communism. The present study was conducted to see whether such differences still exist and how the patterns had changed during the country's first transitional decade.

Methods

All employees at the University of Tartu (UT) were surveyed for smoking habits by means of a questionnaire in 1992 and 2003. The present paper is based on respondents whose faculty or workplace was known (1390 people in 1992, 1790 in 2003). Smoking differences were assessed in terms of regression-based adjusted figures.

Results

While 20% of the male employees smoked daily in 1992, 13% did so in 2003, the figures for females being 10% and 7%, respectively. The prevalence of men's daily smoking varied between faculties and other workplaces in the range 4-30% in 1992, and 0-24% in 2003, with corresponding ranges of 3-21% and 0-10% among females. Men in the medical faculty in both surveys, and those in the faculty of philosophy in the second survey showed higher rates than men in most other faculties, as did women in the faculty of law in the first survey and those in the faculty of philosophy in the second. The figures were usually low in the faculties of sports & exercise, physics & chemistry and mathematics. The sex pattern was reversed in the faculty of law and also in that of economics, where the women smoked more than the men.

Conclusions

Even in this low-smoking academic community, wide smoking differences existed between the faculties and other workplaces. Faculties where physical or mental performance is of prime importance are leading the way towards a smoke-free community, while men in the faculty of philosophy and, paradoxically, men in the medical faculty are lagging behind. The reversed sex ratio in the faculties of law and economics may indicate women's intensified drive for equality in this transitional society. We assume that different professional cultures may introduce variations in smoking patterns, thereby modifying the course of the smoking epidemic.

Brain grey matter deficits in smokers: focus on the cerebellum

Structural cerebral deficiencies in smokers have been well characterized by morphometric investigations focussing on cortical and subcortical structures. Although the role of the cerebellum is increasingly noted in mental and addiction disorders, no reports exist regarding cerebellar alterations in smokers employing a methodology specifically designed to assess the cerebellar morphology. We acquired high-resolution MRI scans from 33 heavy smokers and 22 never-smokers and used a voxel-based morphometry (VBM) approach utilizing the Spatially Unbiased Infratentorial (SUIT) toolbox (Diedrichsen 2006) to provide an optimized and fine-grained exploration of cerebellar structural alterations associated with smoking. Relative to never-smokers, smokers showed significant reductions of grey matter volume in the right cerebellum Crus I. The grey matter volume in Crus I correlated negatively with the amount of nicotine dependence as assessed by means of the Fagerström scale. Since Crus I has been identified as the cognitive division of the cerebellum, the structural deficit may in part mediate cognitive deficits previously reported in smokers. Of note, the dependence-related magnitude of the volume deficit may support the notion that the cerebellum is substantially involved in core mechanisms of drug dependence.

Statistical means to enhance the comparability of data within a pooled analysis of individual data in neurobehavioral toxicology

Meta-analyses of individual participant data (IPD) provide important contributions to toxicological risk assessments. However, comparability of individual data cannot be taken for granted when information from different studies has to be summarized. By means of statistical standardization approaches the comparability of data might be increased. An analysis of individual data on the neurobehavioral impact of manganese (Mn) exemplifies challenges and effects of a multilevel statistical procedure. Confounding from individual-level and study-level covariates was shown by analyses of variance, but could be reduced by linear regressions and z-normalization using data of the respective control groups. Fixed models that were used to estimate the impact of the neurotoxic exposure, provided evidence that the employed procedures, especially the z-normalization, effectively reduced variance that was unrelated to the neurotoxic exposure. Even after this statistical treatment the fixed effect models revealed differences among studies that did not seem to be exhaustively explicable by concentration differences obvious from the Mn biomarker at hand. IPD studies using confounded endpoints as effects markers can be reasonably summarized when appropriate statistical operations are employed. For the data at hand the proposed normalization allowed new insights into exposure-effect relationships, in general it appears appropriate to investigate the effect of the independent variable more closely.