Smoking

Several large, long-running studies have found that smoking significantly increases your risk of Alzheimer's, as does high exposure to secondhand smoke. Smoking, both in old age and in adolescence, is also associated with lower IQs and lower cognitive performance. It appears, however, that this is largely recoverable if you give up smoking.

Smoking has a particularly negative effect in conjunction with alcohol (and unfortunately they are often found in tandem). While moderate drinking can in some circumstances have positive effects on the brain, this is probably not the case for those who smoke. Moreover, smoking makes it much harder for the brain to recover from the effects of alcohol abuse and the damage done to the brain by heavy alcohol consumption is likely to be much worse if the individual is a smoker.

Data from 196,383 older adults (60+; mean age 64) in the UK Biobank found that a healthy lifestyle was associated with lower dementia risk regardless of genes.

Both an unhealthy lifestyle and high genetic risk were associated with higher dementia risk.

Lifestyle factors included smoking, physical activity, diet, and alcohol consumption. Bearing in mind that lifestyle factors were self-reported, 68.1% followed a healthy lifestyle, 23.6% were intermediate, and 8.2% followed an unhealthy lifestyle. Regarding genes, 20% were at high risk, 60% were intermediate, and 20% were at low risk.

Of those at high genetic risk, 1.23% developed dementia in the 8-year period (remember that these are people who are still relatively — the average age at study end would still only be 72), compared with 0.63% of those at low genetic risk. Of those at high genetic risk plus an unhealthy lifestyle, 1.78% developed dementia compared to 0.56% of those at low risk with a healthy lifestyle. Among those who had a high genetic risk but a healthy lifestyle, 1.13% developed dementia in the period.

I trust that these people will continue to be followed — it will be very interesting to see the statistics in another 10 years.

There were 1,769 new cases of dementia during the 8-year study period.

https://www.eurekalert.org/pub_releases/2019-07/jn-ihl071219.php

https://www.theguardian.com/society/2019/jul/14/healthy-lifestyle-may-cut-risk-of-dementia-regardless-of-genes

Brain scans of 9,772 people aged 44 to 79, who were enrolled in the UK Biobank study, have revealed that smoking, high blood pressure, high pulse pressure, diabetes, and high BMI — but not high cholesterol — were all linked to greater brain shrinkage, less grey matter and less healthy white matter.

Smoking, high blood pressure, and diabetes were the most important factors, but there was also a compound effect, with the number of vascular risk factors being associated with greater damage to the brain. On average, those with the highest vascular risk had nearly 3% less volume of grey matter, and one-and-a-half times the damage to their white matter, compared to people who had the lowest risk.

The brain regions affected were mainly those involved in ‘higher-order’ thinking, and those known to be affected early in the development of dementia.

The associations were as strong for middle-aged adults as for older ones, suggesting the importance of tackling these factors early.

While the effect size was small, the findings emphasize how vulnerable the brain is to vascular factors even in relatively healthy adults. This also suggests the potential of lifestyle changes for fighting cognitive decline.

Although this study didn't itself examine cognitive performance in its participants, other studies have shown links between cognitive impairment and vascular risk factors, particularly diabetes, obesity, hypertension, and smoking.

https://www.eurekalert.org/pub_releases/2019-03/esoc-shb030719.php

Cognitive decline in type 2 diabetes linked to white matter hyperintensities

While type 2 diabetes has been associated with cognitive problems, the mechanism has been unclear. Now a study involving 93 people with type 2 diabetes has found that greater white matter hyperintensities (indicative of cerebral small vessel disease) were associated with decreased processing speed (but not with memory or executive function).

https://www.eurekalert.org/pub_releases/2018-09/w-rem091818.php

Cox, Simon R. et al. 2019. Associations between vascular risk factors and brain MRI indices in UK Biobank. European Heart Journal. doi:10.1093/eurheartj/ehz100

[4395] Mankovsky, B., Zherdova N., van den Berg E., Biessels G.-J., & de Bresser J.
(2018).  Cognitive functioning and structural brain abnormalities in people with Type 2 diabetes mellitus.
Diabetic Medicine. 35(12), 1663 - 1670.

 

A large meta-analysis has concluded that having diabetes increases the chance that a person with mild cognitive impairment will progress to dementia by 65%.

There was no consistent evidence that hypertension or cholesterol levels increased the risk of someone with MCI progressing to dementia. Smoking was similarly not associated with increased risk, although the reason for this probably lies in mortality: smokers tend to die before developing dementia.

There was some evidence that having symptoms of psychiatric conditions, including depression, increased the risk of progressing to dementia.

There was some evidence that following a Mediterranean diet decreased the risk of an individual with amnestic MCI progressing to Alzheimer's, and that higher folate levels decrease the risk of progressing from MCI to dementia. The evidence regarding homocysteine levels was inconsistent.

The evidence indicates that level of education does not affect the risk of someone with MCI progressing to dementia.

Do note that all this is solely about progression from MCI to dementia, not about overall risk of developing dementia. Risk factors are complex. For example, cholesterol levels in mid-life are associated with the later development of dementia, but cholesterol levels later in life are not. This is consistent with cholesterol levels not predicting progression from MCI to dementia. Level of education is a known risk factor for dementia, but it acts by masking the damage in the brain, not preventing it. It is not surprising, therefore, that it doesn't affect progression from MCI to dementia, because higher education helps delay the start, it doesn't slow the rate of decline.

Do note also that a meta-analysis is only as good as the studies it's reviewing! Some factors couldn't be investigated because they haven't been sufficiently studied in this particular population (those with MCI).

The long-running Cache County study has previously found that 46% of those with MCI progressed to dementia within three years; this compared with 3% of those (age-matched) with no cognitive impairment at the beginning of the study.

More recently, data from the long-running, population-based Rotterdam study revealed that those diagnosed with MCI were four times more likely to develop dementia, over seven years. compared with those without MCI. Of those with MCI (10% of the 4,198 study participants), 40% had amnestic MCI — the form of MCI that is more closely associated with Alzheimer's disease.

The 2014 study also found that older age, positive APOE-ɛ4 status, low total cholesterol levels, and stroke, were all risk factors for MCI. Having the APOE-ɛ4 genotype and smoking were related only to amnestic MCI. Waist circumference, hypertension, and diabetes were not significantly associated with MCI. This may be related to medical treatment — research has suggested that hypertension and diabetes may be significant risk factors only when untreated or managed poorly.

http://www.theguardian.com/science/occams-corner/2015/feb/24/speeding-up-the-battle-against-slowing-minds

http://www.eurekalert.org/pub_releases/2015-02/ucl-dad022015.php

http://www.eurekalert.org/pub_releases/2014-08/ip-drq080614.php

[3913] Cooper, C., Sommerlad A., Lyketsos C. G., & Livingston G.
(2015).  Modifiable Predictors of Dementia in Mild Cognitive Impairment: A Systematic Review and Meta-Analysis.
American Journal of Psychiatry. 172(4), 323 - 334.

[3914] Tschanz, J. T., Welsh-Bohmer K. A., Lyketsos C. G., Corcoran C., Green R. C., Hayden K., et al.
(2006).  Conversion to dementia from mild cognitive disorder The Cache County Study.
Neurology. 67(2), 229 - 234.

de Bruijn, R.F.A.G. et al. Determinants, MRI Correlates, and Prognosis of Mild Cognitive Impairment: The Rotterdam Study. Journal of Alzheimer’s Disease, Volume 42/Supplement 3 (August 2014): 2013 International Congress on Vascular Dementia (Guest Editor: Amos D. Korczyn), DOI: 10.3233/JAD-132558.

There are five healthy behaviors that appear to significantly reduce the risk of dementia,

A 35-year study that monitored the healthy behaviors of 2,235 Welsh men aged 45 to 59 at the beginning of the study has found that those who consistently followed at least four of these five healthy behaviors — regular exercise, no smoking, acceptable BMI, high fruit and vegetable intake, and low/moderate alcohol intake — experienced a 60% reduction in dementia and cognitive decline compared with people who followed none. They also had 70% fewer instances of diabetes, heart disease, and stroke,.

Exercise was the most important of these factors.

Only 5% of the men were living a healthy lifestyle (i.e., following at least 4 of these healthy behaviors). Just under half of the 2235 men were non-smokers (46%), and around a third (35%) had an acceptable BMI. Only 15 men ate their “5+” daily (!!), so the requirement was reduced to only three or more portions of fruit and vegetables, enabling 18% to reach it. 39% exercised regularly and 59% reported alcohol intake within the guidelines. Only two men managed five healthy behaviors, and 109 managed four; 19% managed three; 36% two; 31% one; 8% couldn’t manage any.

http://www.futurity.org/five-healthy-behaviors-can-reduce-dementia-risk/

http://www.eurekalert.org/pub_releases/2013-12/cu-3ys120913.php

Elwood, P., Galante, J., Pickering, J., Palmer, S., Bayer, A., Ben-Shlomo, Y., … Gallacher, J. (2013). Healthy Lifestyles Reduce the Incidence of Chronic Diseases and Dementia: Evidence from the Caerphilly Cohort Study. PLoS ONE, 8(12), e81877. doi:10.1371/journal.pone.0081877

The study involved 74 non-smokers with amnestic MCI (average age 76), of whom half were given a nicotine patch of 15 mg a day for six months and half received a placebo. Cognitive tests were given at the start of the study and again after three and six months.

After 6 months of treatment, the nicotine-treated group showed significant improvement in attention, memory, speed of processing and consistency of processing. For example, the nicotine-treated group regained 46% of normal performance for age on long-term memory, whereas the placebo group worsened by 26%.

Nicotine is an interesting drug, in that, while predominantly harmful, it can have positive effects if the dose is just right, and if the person’s cognitive state is at a particular level (slipping below their normal state, but not too far below). Too much nicotine will make things worse, so it’s important not to self-medicate.

Nicotine has been shown to improve cognitive performance in smokers who have stopped smoking and previous short-term studies with nicotine have shown attention and memory improvement in people with Alzheimer's disease. Nicotine receptors in the brain are reduced in Alzheimer’s brains.

Because the dose is so crucial, and the effects so dependent on brain state (including, one assumes, whether the person has been a smoker or not), more research is needed before this can be used as a treatment.

[2736] Newhouse, P., Kellar K., Aisen P., White H., Wesnes K., Coderre E., et al.
(2012).  Nicotine treatment of mild cognitive impairment.
Neurology. 78(2), 91 - 101.

In the last five years, three studies have linked lower neighborhood socioeconomic status to lower cognitive function in older adults. Neighborhood has also been linked to self-rated health, cardiovascular disease, and mortality. Such links between health and neighborhood may come about through exposure to pollutants or other environmental stressors, access to alcohol and cigarettes, barriers to physical activity, reduced social support, and reduced access to good health and social services.

Data from the large Women’s Health Initiative Memory Study has now been analyzed to assess whether the relationship between neighborhood socioeconomic status can be explained by various risk and protective factors for poor cognitive function.

Results confirmed that higher neighborhood socioeconomic status was associated with higher cognitive function, even after individual factors such as age, ethnicity, income, education, and marital status have been taken into account. A good deal of this was explained by vascular factors (coronary heart disease, diabetes, stroke, hypertension), health behaviors (amount of alcohol consumed, smoking, physical activity), and psychosocial factors (depression, social support). Nevertheless, the association was still (barely) significant after these factors were taken account of, suggesting some other factors may also be involved. Potential factors include cognitive activity, diet, and access to health services.

In contradiction of earlier research, the association appeared to be stronger among younger women. Consistent with other research, the association was stronger for non-White women.

Data from 7,479 older women (65-81) was included in the analysis. Cognitive function was assessed by the Modified MMSE (3MSE). Neighborhood socioeconomic status was assessed on the basis of: percentage of adults over 25 with less than a high school education, percentage of male unemployment, percentage of households below the poverty line, percentage of households receiving public assistance, percentage of female-headed households with children, and median household income. Around 87% of participants were White, 7% Black, 3% Hispanic, and 3% other. Some 92% had graduated high school, and around 70% had at least some college.

[2523] Shih, R. A., Ghosh-Dastidar B., Margolis K. L., Slaughter M. E., Jewell A., Bird C. E., et al.
(2011).  Neighborhood Socioeconomic Status and Cognitive Function in Women.
Am J Public Health. 101(9), 1721 - 1728.

Previous:

Lang IA, Llewellyn DJ, Langa KM, Wallace RB, Huppert FA, Melzer D. 2008. Neighborhood deprivation, individual socioeconomic status, and cognitive function in older people: analyses from the English Longitudinal Study of Ageing. J Am Geriatr Soc., 56(2), 191-198.

Sheffield KM, Peek MK. 2009. Neighborhood context and cognitive decline in older Mexican Americans: results from the Hispanic Established Populations for Epidemiologic Studies of the Elderly. Am J Epidemiol., 169(9), 1092-1101.

Wight RG, Aneshensel CS, Miller-Martinez D, et al. 2006. Urban neighborhood context, educational attainment, and cognitive function among older adults. Am J Epidemiol., 163(12), 1071-1078.

Binge drinking is, unfortunately, most common among adolescents (12-20 years). But this is a time when brains are still developing. Does this make them more vulnerable to the detrimental effects of excessive alcohol?

A study involving adolescent mice has revealed that not only did an alcoholic binge reduce the activity of many neurotransmitter genes, but that gene expression in adulthood was even more seriously reduced. Although this deficit didn’t translate into problems with spatial learning, adult mice that had been exposed to excess alcohol in adolescence were significantly worse on a reversal learning task. Moreover, certain brain regions (the olfactory bulb and basal forebrain) were smaller.

In humans, it is thought that these impairments might translate into greater difficulty in adapting to changed situations, in evaluating consequences and controlling impulses.

Similarly, another recent study involving teenagers (15-21) has found that activity in the prefrontal cortex varied according to how heavily they smoked, with those who smoked most heavily having the least activity.

The 25 smokers and 25 non-smokers were tested on a Stop-Signal Task, which tests a person’s ability to inhibit an action. Despite the differences in activity level, smokers and non-smokers performed similarly on the task, suggesting that other brain areas are in some way compensating for the impaired prefrontal cortex. Nevertheless, reduced activity in the prefrontal cortex, which is still developing in adolescence, does suggest long-term consequences for decision-making and cognitive control.

Data from 21,123 people, surveyed between 1978 and 1985 when in their 50s and tracked for dementia from 1994 to 2008, has revealed that those who smoked more than two packs per day in middle age had more than twice the risk of developing dementia, both Alzheimer's and vascular dementia, compared to non-smokers.

A quarter of the participants (25.4%) were diagnosed with dementia during the 23 years follow-up, of whom a little over 20% were diagnosed with Alzheimer's disease and nearly 8% with vascular dementia.

Former smokers, or those who smoked less than half a pack per day, did not appear to be at increased risk. Associations between smoking and dementia did not vary by race or sex.

Smoking is a well-established risk factor for stroke, and is also known to contribute to oxidative stress and inflammation.

[1934] Rusanen, M., Kivipelto M., Quesenberry C. P., Zhou J., & Whitmer R. A.
(2010).  Heavy Smoking in Midlife and Long-term Risk of Alzheimer Disease and Vascular Dementia.
Arch Intern Med. archinternmed.2010.393 - archinternmed.2010.393.

Comparison of the brains of 22 smokers and 21 people who have never smoked in their lives has revealed that the left medial orbitofrontal cortex of the smokers was on average smaller than that of the non-smokers. Moreover, this reduction was greater the more cigarettes were smoked daily, and as a function of how long they had smoked. The region is involved in reward, impulse control, and decision-making, suggesting that fewer neurons there may mean you have to work harder for reward, and that your ability to curb your impulses and make decisions is impaired.

While it may be that smoking is affecting this damage, it may also be that those with a smaller orbitofrontal cortex are more likely to smoke (perhaps it is most likely that both are true!). Further research will need to distinguish these two possibilities.

[1923] Kühn, S., Schubert F., & Gallinat J.
(Submitted).  Reduced Thickness of Medial Orbitofrontal Cortex in Smokers.
Biological Psychiatry. In Press, Corrected Proof,

A 12-year study following the drinking and smoking habits of 22,524 people aged 39-79 has found that in non-smokers, people who consumed moderate amounts of alcohol were 37% less likely to develop stroke than non-drinkers. This association was not found among smokers. The finding may explain the inconsistency in previous studies into the relationship between light to moderate drinking and stroke.

The findings were presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto, April 10 - 17, 2010.

Data from more than 20,000 18-year-old Israeli men has revealed that IQ scores are lower in male adolescents who smoke compared to non-smokers, and in twin brothers who smoke compared to their non-smoking brothers. The average IQ for a non-smoker was about 101, while the smokers' average was about 94, with those who smoked more than a pack a day being lower still, at about 90. 28% of the sample smoked one or more cigarettes a day, 3% identified as ex-smokers, and 68% said they never smoked.

Older news items (pre-2010) brought over from the old website

Second-hand smoke linked to cognitive impairment

Smoking is known to be a risk factor for cognitive impairment and dementia. Now a large study of some 4800 non-smoking adults over the age of 50 has revealed that exposure to second-hand smoke (measured by levels of a nicotine by-product in their saliva) is associated with an increased chance of developing cognitive impairment, including dementia.

[641] Llewellyn, D. J., Lang I. A., Langa K. M., Naughton F., & Matthews F. E.
(2009).  Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement.
BMJ. 338(feb12_2), b462 - b462.

The open-access article is available here.
http://www.eurekalert.org/pub_releases/2009-02/uoc-ssl021209.php

Midlife smokers may have worse memory than non-smokers

Data from the very large Whitehall II study has found that those who smoked were more likely to be in the lowest 20% for cognitive performance compared with those who had never smoked. Those who reported being ex-smokers at the beginning of the study were 30% less likely than smokers to have poor vocabulary and low verbal frequency scores, showing that recovery is likely if smoking is stopped. The study also found a higher risk of death as well as non-participation in cognitive tests among smokers, suggesting the association between smoking and cognition may have been under-estimated.

[476] Sabia, S., Marmot M., Dufouil C., & Singh-Manoux A.
(2008).  Smoking History and Cognitive Function in Middle Age From the Whitehall II Study.
Arch Intern Med. 168(11), 1165 - 1173.

http://www.eurekalert.org/pub_releases/2008-06/jaaj-msm060508.php

Smokers are more likely to develop dementia

A seven-year study of some 7,000 people age 55 and older found that those who were current smokers at the time of the study were 50% more likely to develop dementia than people who had never smoked or past smokers. Smoking did not increase the risk for those with the Alzheimer’s gene apolipoprotein E4. Current smokers without the gene were nearly 70% more likely to develop Alzheimer’s than nonsmokers or past smokers without the gene.

[2381] Reitz, C., den Heijer T., van Duijn C., Hofman A., & Breteler M. M. B.
(2007).  Relation between smoking and risk of dementia and Alzheimer disease.
Neurology. 69(10), 998 - 1005.

http://www.eurekalert.org/pub_releases/2007-09/aaon-sam082807.php

Secondhand smoke increases risk of dementia

Preliminary findings from the Cardiovascular Health Study indicates that elderly people with high lifetime exposure to secondhand smoke (more than 30 years) were approximately 30% more likely to develop dementia than those with no lifetime secondhand smoke exposure. People with abnormalities of their carotid arteries and high lifetime exposure to secondhand smoke were nearly two-and-a-half times as likely to develop dementia as those with no secondhand smoke exposure and no indications of carotid artery disease.

Haight presented the findings at the American Academy of Neurology’s 59th Annual Meeting in Boston, April 28 – May 5, 2007.

http://www.eurekalert.org/pub_releases/2007-05/aaon-ssi041007.php

Smoking now found detrimental for Alzheimer’s

Previous animal studies had suggested that nicotine reduces the number of amyloid plaques; a new study, however, has found that chronic nicotine exposure increases neurofibrillary tangles.

[2380] Oddo, S., Caccamo A., Green K. N., Liang K., Tran L., Chen Y., et al.
(2005).  Chronic nicotine administration exacerbates tau pathology in a transgenic model of Alzheimer's disease.
Proceedings of the National Academy of Sciences of the United States of America. 102(8), 3046 - 3051.

http://www.eurekalert.org/pub_releases/2005-02/uoc--ctp020805.php

Smoking associated with working memory impairment in adolescents

A study of 41 adolescent daily smokers and 32 nonsmokers has revealed that adolescent smokers had impairments in accuracy of working memory performance. Male adolescents as a group begin smoking at an earlier age than female smokers and were significantly more impaired during tests of selective and divided attention. All of the adolescent smokers also showed further disruption of working memory when they stopped smoking.

[1252] Jacobsen, L. K., Krystal J. H., Mencl E. W., Westerveld M., Frost S. J., & Pugh K. R.
(2005).  Effects of smoking and smoking abstinence on cognition in adolescent tobacco smokers.
Biological Psychiatry. 57(1), 56 - 66.

http://www.eurekalert.org/pub_releases/2005-02/yu-scc020105.php

Smoking is bad for the brain

465 participants in the Scottish Mental Survey (11 year olds tested in 1947), approximately half of whom were smokers, were tested again when they were 64. Smokers performed significantly worse in five different cognitive tests than did both former smokers and those who had never smoked. This drop in cognitive function held when factors such as education, occupation and alcohol consumption were taken into account. A link between impaired lung function and cognitive ageing has long been suspected, though the mechanism is unclear.

[2382] Whalley, L. J., Fox H. C., Deary I. J., & Starr J. M.
(2005).  Childhood IQ, smoking, and cognitive change from age 11 to 64 years.
Addictive Behaviors. 30(1), 77 - 88.

http://www.newscientist.com/news/news.jsp?id=ns99996765

Smoking and alcohol

Smoking may counteract benefit of moderate drinking on stroke risk

A 12-year study following the drinking and smoking habits of 22,524 people aged 39-79 has found that in non-smokers, people who consumed moderate amounts of alcohol were 37% less likely to develop stroke than non-drinkers. This association was not found among smokers. The finding may explain the inconsistency in previous studies into the relationship between light to moderate drinking and stroke.

The findings were presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto, April 10 - 17, 2010.

www.physorg.com/news190375547.html

Smoking interferes with recovery from alcohol-related brain damage

Another study has come out with more evidence that smoking makes it a lot harder for the brain to recover from the effects of long-term heavy drinking. The study looked specifically at changes in blood flow in the brain — blood flow is affected by alcohol use disorders. The study found that after 5 weeks of abstinence, alcohol-dependent individuals who didn’t smoke showed significantly improved blood flow, but those who smoked showed essentially no change. Moreover, the number of cigarettes smoked daily was correlated with how poorly the blood was flowing in the frontal lobe.

[1045] Mon, A., Durazzo T. C., Gazdzinski S., & Meyerhoff D. J.
(2009).  The impact of chronic cigarette smoking on recovery from cortical gray matter perfusion deficits in alcohol dependence: longitudinal arterial spin labeling MRI.
Alcoholism, Clinical and Experimental Research. 33(8), 1314 - 1321.

http://www.eurekalert.org/pub_releases/2009-05/ace-siw050509.php

Alzheimer's starts earlier for heavy drinkers, smokers

A study of nearly 1000 people diagnosed with possible or probable Alzheimer’s disease has found that those who were heavy drinkers developed Alzheimer’s 4.8 years earlier than those who were not, while heavy smokers developed the disease 2.3 years sooner than people who were not heavy smokers. Those with the APOE å4 gene developed the disease three years sooner than those without the gene variant. The risk factors are additive — those with all three risk factors developed the disease 8.5 years earlier than those with none of the risk factors.

The research was presented at the American Academy of Neurology Annual Meeting in Chicago, April 12 – April 19.

http://www.eurekalert.org/pub_releases/2008-04/aaon-ase040208.php

Nicotine may enhance attention and working memory in recovering alcoholics

New findings show that nicotine patches may enhance cognitive functioning among newly recovering alcoholics with a history of smoking. Nicotine (but not tobacco) has been shown to have a cognitive benefit, particularly on attention processes. The study also found that alcoholics who smoked were more sensitive to the drug dose of nicotine than were community controls who also smoked.

[1006] Nixon, S J., Lawton-Craddock A., Tivis R., & Ceballos N.
(2007).  Nicotine's Effects on Attentional Efficiency in Alcoholics.
Alcoholism: Clinical and Experimental Research. 31(12), 2083 - 2091.

http://www.eurekalert.org/pub_releases/2007-11/ace-nme111907.php

Smoking interferes with brain's recovery from alcoholism

In another study indicating smoking worsens the effect of alcoholism on the brain, smoking was found to apparently interfere with the brain's ability to recover from the effects of chronic alcohol abuse.

[2371] Durazzo, T. C., Gazdzinski S., Rothlind J. C., Banys P., & Meyerhoff D. J.
(2006).  Brain Metabolite Concentrations and Neurocognition During Short‐term Recovery from Alcohol Dependence: Preliminary Evidence of the Effects of Concurrent Chronic Cigarette Smoking.
Alcoholism: Clinical and Experimental Research. 30(3), 539 - 551.

http://www.eurekalert.org/pub_releases/2006-03/uoc--siw031506.php

Long-term smoking associated with dulled thinking and lower IQ

A long-term study involving 172 alcoholic and non-alcoholic men has found that long-term smoking impaired memory and reasoning skills and reduced IQ. The effect was most pronounced among those who had smoked for years. The effects of smoking were found among the non-alcoholics as well as the alcoholics, and among the alcoholics, the cognitive impact of long-term heavy smoking appeared to be greater than the impact of drinking.

[1116] Glass, J. M., Adams K. M., Nigg J. T., Wong M. M., Puttler L. I., Buu A., et al.
(2006).  Smoking is associated with neurocognitive deficits in alcoholism.
Drug and Alcohol Dependence. 82(2), 119 - 126.

http://www.eurekalert.org/pub_releases/2005-10/uomh-dsc101005.php

Smoking seems to increase brain damage in alcoholics

Another study has come out indicating that alcoholics who smoke are at greater risk of brain damage. The imaging study compared brain volume in recovered alcoholics and light drinkers. The study found no difference between smokers and non-smokers among the light drinkers, but among the alcoholics, the more severe the tobacco habit, the more brain volume had been lost.

[1049] Gazdzinski, S., Durazzo T. C., Studholme C., Song E., Banys P., & Meyerhoff D. J.
(2005).  Quantitative Brain MRI in Alcohol Dependence: Preliminary Evidence for Effects of Concurrent Chronic Cigarette Smoking on Regional Brain Volumes.
Alcoholism: Clinical and Experimental Research. 29(8), 1484 - 1495.

http://www.eurekalert.org/pub_releases/2005-09/uoc--sst092805.php

Cigarette smoking exacerbates alcohol-induced brain damage

Heavy alcohol consumption is known to cause brain damage. A new imaging study has compared 24, one-week-abstinent alcoholics (14 smokers, 10 nonsmokers) in treatment with 26 light-drinking "controls" (7 smokers, 19 nonsmokers), and found that cigarette smoking can both exacerbate alcohol-induced damage as well as independently cause brain damage. The damage is most prominent in the frontal lobes (important in planning, decision-making, and multi-tasking among other functions). Independent of alcohol consumption, cigarette smoking also had adverse effects on brain regions involved in fine and gross motor functions and balance and coordination. Roughly 80% of alcohol-dependent individuals report smoking regularly.

[2370] Durazzo, T. C., Gazdzinski S., Banys P., & Meyerhoff D. J.
(2004).  Cigarette Smoking Exacerbates Chronic Alcohol‐Induced Brain Damage: A Preliminary Metabolite Imaging Study.
Alcoholism: Clinical and Experimental Research. 28(12), 1849 - 1860.

http://www.eurekalert.org/pub_releases/2004-12/ace-cse120504.php

Benefits of nicotine

Nicotine patch may alleviate 'senior moments'

A small preliminary clinical trial has found that four weeks of nicotine skin patches helped decision-making and attention in people with age-associated memory impairment (the mildest form of cognitive impairment in seniors). Given the health risks of smoking, and health risks associated with nicotine patches, it is too early to recommend the use of nicotine to improve memory, however. Nicotine mimics the brain chemical acetylcholine, a nerve signal that plays a role in learning and memory.

[2383] White, H. K., & Levin E. D.
(2004).  Chronic transdermal nicotine patch treatment effects on cognitive performance in age-associated memory impairment.
Psychopharmacology. 171(4), 465 - 471.

http://www.eurekalert.org/pub_releases/2003-12/dumc-npm120303.php