Smoking increases risk for cognitive decline among community-dwelling older Mexican Americans

A synergistic effect of secondhand smoke with vitamin D deficiency on cognitive impairment in older adults: a cross sectional study

Objectives

To investigate whether exposure to secondhand smoke (SHS) aggravates the detrimental effect of vitamin D deficiency (VDD) on cognitive performance in the elderly.

Methods

Based on National Health and Nutrition Examination Surveys (NHANES) 2011-2014, 1,446 non-smoking participants (≥ 60 years old) with detailed serum 25-hydroxyvitamin D [25(OH)D], concentration of cotinine and tests score of cognitive function were included. Cognitive impairment was defined as having a cognitive score in the lowest quartile. The possible synergistic effect of SHS with VDD on cognitive impairment was evaluated by using a multivariable logistic regression model.

Results

VDD was independently associated with risk of low the Digit Symbol Substitution Test (DSST) scores, increased by nearly 60% [< 34, adjusted odds ratio (aOR) = 1.62, 95% CI: 1.03 ~ 2.53]. Although it only had an association with cognitive impairment indicated by DSST and the Animal Fluency test (AFT) in the crude model, SHS exposure showed significant synergistic effects with VDD on DSST (aOR: 3.03, 95% CI: 1.57 ~ 5.83, Pinteraction = 0.001) and AFT (aOR: 2.40, 95% CI: 1.34 ~ 4.29, Pinteraction = 0.003), respectively, after adjusting for the possible confounders. In further stratified analysis, a more obvious synergistic effect of SHS with VDD on DSST (aOR: 4.73, 95%CI:1.77 ~ 12.68, Pinteraction = 0.002) and AFT (aOR: 5.30, 95%CI: 1.63 ~ 17.24, Pinteraction = 0.006) was found in obese and overweight subjects, respectively.

Conclusion

SHS exposure had synergistic effect with VDD on cognitive impairment among elderly and the interaction effect was more obvious in overweight and obese individuals.

Integrative blood-based characterization of oxidative mitochondrial DNA damage variants implicates Mexican American's metabolic risk for developing Alzheimer's disease

Alzheimer's Disease (AD) continues to be a leading cause of death in the US. As the US aging population (ages 65 +) expands, the impact will disproportionately affect vulnerable populations, e.g., Hispanic/Latino population, due to their AD-related health disparities. Age-related regression in mitochondrial activity and ethnic-specific differences in metabolic burden could potentially explain in part the racial/ethnic distinctions in etiology that exist for AD. Oxidation of guanine (G) to 8-oxo-guanine (8oxoG) is a prevalent lesion and an indicator of oxidative stress and mitochondrial dysfunction. Damaged mtDNA (8oxoG) can serve as an important marker of age-related systemic metabolic dysfunction and upon release into peripheral circulation may exacerbate pathophysiology contributing to AD development and/or progression. Analyzing blood samples from Mexican American (MA) and non-Hispanic White (NHW) participants enrolled in the Texas Alzheimer's Research & Care Consortium, we used blood-based measurements of 8oxoG from both buffy coat PBMCs and plasma to determine associations with population, sex, type-2 diabetes, and AD risk. Our results show that 8oxoG levels in both buffy coat and plasma were significantly associated with population, sex, years of education, and reveal a potential association with AD. Furthermore, MAs are significantly burdened by mtDNA oxidative damage in both blood fractions, which may contribute to their metabolic vulnerability to developing AD.

Association of air pollution with dementia: a systematic review with meta-analysis including new cohort data from China

It remains unclear whether a total exposure to air pollution (AP) is associated with an increased risk of dementia. Little is known on the association in low- and middle-income countries. Two cohort studies in China (in Anhui cohort 1402 older adults aged ≥ 60 followed up for 10 years; in Zhejiang cohort 6115 older adults followed up for 5 years) were conducted to examine particulate matter - PM_2.5 associated with all dementia and air quality index (AQI) with Alzheimer's disease, respectively. A systematic literature review and meta-analysis was performed following worldwide literature searched until May 20, 2020 to identify 15 population-based cohort studies examining the association of AP with dementia (or any specific type of dementia) through PubMed, MEDLINE, PsycINFO, SocINDEX, CINHAL, and CNKI. The cohort studies in China showed a significantly increased relative risk (RR) of dementia in relation to AP exposure; in Anhui cohort the adjusted RR was 2.14 (95% CI 1.00-4.56) in people with PM_2.5 exposure at ≥ 64.5 μg/m³ versus <63.5 μg/m³ and in Zhejiang cohort the adjusted RR was 2.28 (1.07-4.87) in AQI>90 versus ≤ 80. The systematic review revealed that all 15 studies were undertaken in high income countries/regions, with inconsistent findings. While they had reasonably good overall quality of studies, seven studies did not adjust smoking in analysis and 13 did not account for depression. Pooling all eligible data demonstrated that dementia risk increased with the total AP exposure (1.13, 1.08-1.19). Data analysis of air pollutants showed that the RR significantly increased with PM_2.5 (1.06, 1.03-1.10 in 2nd tertile exposure; 1.13, 1.07-1.19 in 3rd tertile versus 1st tertile), PM₁₀ (1.05, 0.86-1.29; 1.62, 0.60-4.36), carbon monoxide (1.69, 0.72-3.93; 1.52, 1.35-1.71), nitrogen dioxide (1.06, 1.03-1.09; 1.18, 1.10-1.28) and nitrogen oxides (1.09, 1.04-1.15; 1.26, 1.13-1.41), but not ozone. Controlling air pollution and targeting on specific pollutants would reduce dementia globally.

Integrative Blood-Based Characterization of Oxidative Mitochondrial DNA Damage Variants Implicates Mexican Americans' Metabolic Risk for Developing Alzheimer's Disease

Alzheimer's Disease (AD) continues to be a leading cause of death in the US. As the US aging population (ages 65+) expands, the impact will disproportionately affect vulnerable populations, e.g., Hispanic/Latinx population, due to their AD-related health disparities. Age-related regression in mitochondrial activity and ethnic-specific differences in metabolic burden could potentially explain in part the racial/ethnic distinctions in etiology that exist for AD. Oxidation of guanine (G) to 8-oxo-guanine (8oxoG) is a prevalent lesion and an indicator of oxidative stress and mitochondrial dysfunction. Damaged mtDNA (8oxoG) can serve as an important marker of age-related systemic metabolic dysfunction and upon release into peripheral circulation may exacerbate pathophysiology contributing to AD development and/or progression. Analyzing blood samples from Mexican American (MA) and non-Hispanic White (NHW) participants enrolled in the Texas Alzheimer's Research & Care Consortium, we used blood-based measurements of 8oxoG from both buffy coat PBMCs and plasma to determine associations with population, sex, type-2 diabetes, and AD risk. Our results show that 8oxoG levels in both buffy coat and plasma were significantly associated with population, sex, years of education, and reveal a potential association with AD. Furthermore, MAs are significantly burdened by mtDNA oxidative damage in both blood fractions, which may contribute to their metabolic vulnerability to developing AD.

Nutritional status, alcohol-tobacco consumption behaviour and cognitive decline among older adults in India

Cognition capacity is essentially age-dependent and it is associated with the overall well-being of an individual. The public health aspects of cognitive research primarily focus on the possible delaying of cognitive decline among the older adult population. In this context, using the most recent round of the Longitudinal Ageing Study in India, 2017-2018 data, this study examines the cognition capacity among older adults aged 45 and above subject to their nutritional health and health behaviour (tobacco and alcohol consumption). It is observed that almost one in every tenth individual (10%) above 45 years of age in India shows low cognition scores. Low cognition is much more prevalent among 60 + females than males. Around one-fifth of the underweight older adults (18%) demonstrate low cognition capacity among them. Of those older adults who consume only tobacco, 11% of them demonstrate low cognition than the rest. The partial proportional odds model estimation shows that older adults are at higher risk of developing low cognition with increasing age and beyond age 65, the individuals carry a critically higher risk to experience low cognition. The estimation also shows that with increasing age older adults are higher likely to experience poor cognition independent of nutritional status, but underweight older adults are comparatively more likely to experience low cognition followed by normal and overweight older adults. In terms of alcohol-tobacco consumption behaviour, older adults who consume both are more likely to experience low cognition with increasing age followed by 'only alcohol consumers', and 'only tobacco consumers'.

Cognitive decline trajectories and influencing factors in China: A non-normal growth mixture model analysis

BACKGROUND

With the increase in the aging population worldwide, cognitive decline has become an important research topic. The purpose of this study is to examine the cognitive development trajectories and influencing factors of different latent classes of Chinese elderly people. This will provide us with effective guidance for prevention and intervention.

METHODS

Four waves of data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) were collected and included 2440 Chinese elderly individuals. The cognitive function of elderly individuals was measured using the Mini Mental State Examination (MMSE). A nonnormal Growth Mixture model (GMM) with five time-invariant covariates was used to identify the different trajectories of cognitive decline in elderly individuals.

RESULTS

Three latent decline trajectory groups were identified: stable cognitive group (SCG), high initial level - cognitive decline group (HIL-CDG), and high initial level - cognitive decline group (LIL-CDG). Elderly women were more likely to be assigned to a lower level subgroup than men. People who smoked and played cards or mahjong were more likely to be assigned to a cognitively stable group.

CONCLUSION

Education may help raise the upper limit of cognition. Smoking may impair cognitive upper limit. A small amount of alcohol intake and participation in cognitive and physical activities may help the elderly to delay cognitive decline in their later years.

Associations between metabolic syndrome and type of dementia: analysis based on the National Health Insurance Service database of Gangwon province in South Korea

BACKGROUND

Metabolic syndrome is a cluster of conditions that occur together, increasing the risk of cardiovascular disease. However, the relationship between metabolic syndrome and dementia has remained controversial. Using nationwide population cohort data, we investigated the association between metabolic syndrome and dementia, according to the dementia type.

METHODS

We analyzed data of 84,144 individuals, in the aged group of more than 60 years, between January 1, 2009, to December 31, 2009, at Gangwon province by using the information of the (Korean) National Health Insurance Service. After eight years of gap, in 2017, we investigated the relationship between metabolic syndrome and dementia. We classified Dementia either as dementia of the Alzheimer type (AD) or vascular dementia (VD). AD and VD were defined as per the criteria of International Classification of Disease, Tenth Revision, Clinical Modification codes. Multiple logistic regression analyses examined the associations between metabolic syndrome or five metabolic syndrome components and dementia. Analyses included factors like age, sex, smoking, alcohol, physical inactivity, previous stroke, and previous cardiac disease.

RESULTS

Metabolic syndrome was associated with AD (OR = 11.48, 95% CI 9.03-14.59), not with VD. Each of five components of metabolic syndrome were also associated with AD. (high serum triglycerides: OR = 1.87, 95% CI 1.60-2.19; high blood pressure: OR = 1.85, 95% CI 1.55-2.21; high glucose: OR = 1.77, 95% CI 1.52-2.06; abdominal obesity: OR = 1.88, 95% CI 1.57-2.25; low serum high-density lipoprotein cholesterol: OR = 1.91, 95% CI 1.63-2.24) However, among components of metabolic syndrome, only the high glucose level was associated with VD. (OR = 1.26, 95% CI 1.01-1.56) body mass index (BMI), fasting glucose, and smoking were also associated with AD. (BMI: OR = 0.951, 95% CI 0.927-0.975; fasting glucose: OR = 1.003, 95% CI 1.001-1.005; smoking: OR = 1.020, 95% CI 1.003-1.039) A history of the previous stroke was associated with both AD and VD. (AD: OR = 1.827, 95% CI 1.263-2.644; VD: OR 2.775, 95% CI 1.747-4.406) CONCLUSIONS: Metabolic syndrome was associated with AD but not with VD. Patients with metabolic syndrome had an 11.48 times more likeliness to develop AD compared to those without metabolic syndrome. VD was associated only with several risk factors that could affect the vascular state rather than a metabolic syndrome. We suggested that the associations between metabolic syndrome and dementia would vary depending on the type of dementia.

The long-term effect of intra-European migration on cognitive abilities in later life

The study raises the question about the long-term effect of intra-European migration on cognitive abilities in later life. In contrast to previous research that compares migrants to natives of the destination country, this study uses stayers in the European origin countries as reference group for migrants who moved to another European country earlier in life and are now growing old abroad. Selection into migration is addressed methodologically by applying an instrumental variable approach. Using the Global Bilateral Migration Database to generate the country- and time-specific share of emigrants as instrument for migration, the results indicate that intra-European migration turns out to have a negative long-term effect on the level of cognitive abilities.

Cigarette smoking and cognitive function among older adults living in the community

Background. The present study aimed to examine the long-term impact of CS on Executive Function (EF) and memory among older adults living in the community. Methods. Clock Drawing Test (CDT) and Delayed Word Recall Test (DWRT) were used to examine EF and memory, respectively, using four waves of National Health and Aging Trend Study. The respondents were asked whether they have ever smoked, length of smoking, and age of start and quit smoking. Results. CS can have a long-term impact on both EF and memory. However, current smoking can increase the risk of EF impairment compared to former smokers. Lung disease and current smoking can have a synergic effect of impairment in EF. Conclusion. In the long-term, smoking can negatively affect cognitive. Lung diseases and smoking can synergize their impacts on EF. The impact of smoking on cognition varies across ethnic groups; hence, educational programs targeting minorities can reduce discrepancies.

Cognitive Functioning and Associated Factors in Older Adults: Results from the Indonesian Family Life Survey-5 (IFLS-5) in 2014-2015

Objective

The study aims to investigate cognitive functioning and associated factors in a national general population-based sample of older Indonesians.

Methods

Participants were 1228 older adults, 65 years and older (median age 70.0 years, Interquartile Range=6.0), who took part in the cross-sectional Indonesian Family Life Survey-5 (IFLS-5) in 2014-15. They were requested to provide information about sociodemographic and various health variables, including cognitive functioning measured with items from the Telephone Survey of Cognitive Status (TICS). Multivariable linear regression analysis was performed to assess the association of sociodemographic factors, health variables, and cognitive functioning.

Results

The overall mean cognition score was 14.7 (SD=4.3) (range 0-34). In adjusted linear regression analysis, older age, having hypertension, and being underweight were negatively associated with better cognitive functioning and higher education was positively associated with better cognitive functioning.

Conclusion

Several sociodemographic and health risk factors for poor cognitive functioning were identified which can guide intervention strategies in Indonesia.

The Role of Education in the Relationship Between Age of Migration to the United States and Risk of Cognitive Impairment Among Older Mexican Americans

Prior research indicates age of migration is associated with cognitive health outcomes among older Mexican Americans; however, factors that explain this relationship are unclear. This study used eight waves from the Hispanic Established Populations for the Epidemiologic Study of the Elderly to examine the role of education in the risk for cognitive impairment (CI) by nativity, age of migration, and gender. Foreign-born women had a higher risk for CI than U.S.-born women, regardless of age of migration. After adjusting for education, this risk remained significant only for late-life migrant women (risk ratio [RR] = 1.28). Foreign-born men who migrated at >50 had significantly higher risk for CI compared to U.S.-born men (RR = 1.33) but not significant after adjusting for education. Findings from a decomposition analysis showed education significantly mediated the association between age of migration and CI. This study highlights the importance of education in explaining the association between age of migration and CI.

Age of Migration and the Incidence of Cognitive Impairment: A Cohort Study of Elder Mexican-Americans

BACKGROUND AND OBJECTIVES

To explore nativity and age of migration differentials in the incidence of cognitive impairment among older Mexican-Americans.

RESEARCH DESIGN AND METHODS

We employ maximum-likelihood discrete time hazard models to estimate risk ratios of cognitive impairment in a sample of 2,708 Mexican-Americans 65 and older who were cognitively healthy at baseline over a follow-up period of up to 20 years.

RESULTS

Late-life immigrant women have a 46% higher risk of cognitive impairment compared to U.S.-born Mexican-American women. Conversely, midlife immigrant men have a 29% lower risk of cognitive impairment compared to U.S.-born Mexican-American men. The incidence of cognitive impairment did not differ for early-life and midlife immigrant women relative to U.S.-born women or for early- and late-life immigrant men compared to U.S.-born men.

DISCUSSION AND IMPLICATIONS

Differences in cognitive impairment risk between U.S.-born and foreign-born Mexican-American subgroups may be partly due to health selectivity. Cognitive impairment is more prevalent among immigrant groups which may result in a higher burden on family members and/or high dependency on public resources. Programs are needed that can detect decline at earlier stages and reduce the risk for cognitive impairment among older immigrants entering their last decades of life.

The Hispanic Paradox: Race/Ethnicity and Nativity, Immigrant Enclave Residence and Cognitive Impairment Among Older US Adults

Hispanics, and particularly foreign-born Mexican Americans, have been shown to fare better across a range of health outcomes than might be expected given the generally higher levels of socioeconomic disadvantage in this population, a phenomena termed the "Hispanic Paradox". Previous research on social disparities in cognitive aging, however, has been unable to address both race/ethnicity and nativity (REN) in a nationally-representative sample of US adults leaving unanswered questions about potentially "paradoxical" advantages of Mexican ethnic-origins and the role of nativity, socioeconomic status (SES), and enclave residence. We employ biennial assessments of cognitive functioning to study prevalent and incident cognitive impairment (CI) within the three largest US REN groups: US-born non-Hispanic whites (US-NHW), US-born non-Hispanic blacks (US-NHB), US-born Mexican Americans (US-MA), and foreign-born Mexican Americans (FB-MA). Data come from a nationally-representative sample of community-dwelling older adults in the Health and Retirement Study linked with the 2000 Census and followed over 10 years (N = 8,433). Large disadvantages in prevalent and incident CI were observed for all REN minorities respective to US-born non-Hispanic whites. Individual and neighborhood SES accounted substantially for these disadvantages and revealed an immigrant advantage: FB-MA odds of prevalent CI were about half those of US-NHW and hazards of incident CI were about half those of US-MA. Residence in an immigrant enclave was protective of prevalent CI among FB-MA. The findings illuminate important directions for research into the sources of cognitive risk and resilience and provide guidance about CI screening within the increasingly diverse aging US population.

Association of midlife smoking status with change in processing speed and mental flexibility among HIV-seropositive and HIV-seronegative older men: the Multicenter AIDS Cohort Study

Smoking is a potential risk factor for age-related cognitive decline. To date, no study has examined the association between smoking and cognitive decline in men living with human immunodeficiency virus (HIV). The aim of this present study is to examine whether smoking status and severity in midlife is associated with a rate of decline in cognitive processing speed among older HIV-seropositive and HIV-seronegative men who have sex with men. Data from 591 older HIV-seropositive and HIV-seronegative men who have sex with men from the Multicenter AIDS Cohort Study were examined. All participants had information on smoking history collected before age 50 years and at least 5 years of follow-up after age 50. Smoking history was categorized as never smoker, former smoker, and current smoker and cumulative pack years was calculated. The raw scores of three neuropsychological tests (Trail Making A, Trail Making B, and Symbol Digit Modalities tests) were log transformed (Trail Making A and B) and used in linear mixed models to determine associations between smoking history and at least subsequent 5-year decline in cognitive processing speed. There were no significant differences in the rates of neurological decline among never smokers, former smokers, and current smokers. Findings were similar among HIV-seropositive participants. However, an increase of 5 pack-years was statistically significantly associated with a greater rate of decline in the Trail Making Test B score and Composite Score (β -0.0250 [95% CI, -0.0095 to -0.0006] and -0.0077 [95% CI, -0.0153 to -0.0002], respectively). We found no significant association between smoking treated as a categorical variable (never smoked, former smoker, or current smoker) and a small change in every increase of 5 pack-years on measures of psychomotor speed and cognitive flexibility. To optimize healthy aging, interventions for smoking cessation should be tailored to men who have sex with men.

Change in Cognitive Abilities in Older Latinos

The aim of this study was to compare patterns of cognitive decline in older Latinos and non-Latinos. At annual intervals for a mean of 5.7 years, older Latino (n=104) and non-Latino (n=104) persons of equivalent age, education, and race completed a battery of 17 cognitive tests from which previously established composite measures of episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability were derived. In analyses adjusted for age, sex, and education, performance declined over time in each cognitive domain, but there were no ethnic group differences in initial level of function or annual rate of decline. There was evidence of retest learning following the baseline evaluation, but neither the magnitude nor duration of the effect was related to Latino ethnicity, and eliminating the first two evaluations, during which much of retest learning occurred, did not affect ethnic group comparisons. Compared to the non-Latino group, the Latino group had more diabetes (38.5% vs. 25.0; χ2[1]=4.4; p=.037), fewer histories of smoking (24.0% vs. 39.4%, χ2[1]=5.7; p=.017), and lower childhood household socioeconomic level (-0.410 vs. -0.045, t[185.0]=3.1; p=.002), but controlling for these factors did not affect results. Trajectories of cognitive aging in different abilities are similar in Latino and non-Latino individuals of equivalent age, education, and race. (JINS, 2016, 22, 58-65).

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.

Target risk factors for dementia prevention: a systematic review and Delphi consensus study on the evidence from observational studies

OBJECTIVE

Dementia has a multifactorial etiology, but the importance of individual health and lifestyle related risk factors is often uncertain or based on few studies. The goal of this paper is to identify the major modifiable risk factors for dementia as a first step in developing an effective preventive strategy and promoting healthy late life cognitive functioning.

METHODS

A mixed-method approach combined findings from a systematic literature review and a Delphi consensus study. The literature search was conducted in PubMed and updated an earlier review by the United States National Institutes of Health from 2010. We reviewed the available evidence from observational epidemiological studies. The online Delphi study asked eight international experts to rank and weigh each risk factor for its importance for dementia prevention.

RESULTS

Out of 3127 abstracts, 291 were included in the review. There was good agreement between modifiable risk factors identified in the literature review and risk factors named spontaneously by experts. After triangulation of both methods and re-weighting by experts, strongest support was found for depression, (midlife) hypertension, physical inactivity, diabetes, (midlife) obesity, hyperlipidemia, and smoking, while more research is needed for coronary heart disease, renal dysfunction, diet, and cognitive activity.

CONCLUSIONS

Findings provide good support for several somatic and lifestyle factors and will be used to inform the design of a new multicenter trial into dementia prevention.

Risk Factors Related to Cognitive Functioning: A Cross-National Comparison of U.S. and Korean Older Adults

The purpose of this study was to conduct a cross-national comparison of factors related to cognitive functioning in later life in a U.S. and Korean sample. The study sample was comprised of subjects from the HRS ( N = 10,175) and the KLoSA ( N = 3,550). Separate multivariate regression models were employed to examine the impact of socio-demographic, health, and health behaviors on cognitive functioning among older adults. Regression results showed that age, gender, education, wealth, self-rated health, ADL, IADL, stroke, and poor eyesight were significantly associated with cognitive functioning in both countries. However, depression, high blood pressure, diabetes, and drinking were significantly associated with cognition only among Americans, while marital status and poor hearing were significantly associated with cognition only among Koreans. In addition, gender-specific models suggested several socio-economic and health factors had significantly different effects by gender in both countries. Cross-national comparative research identified similar risk factors, suggesting robust associations. Unique factors related to cognitive functioning in U.S. and Korean older adults highlight the important role of societal influences on cognitive outcomes.

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.

Association between tobacco smoking and cognitive functioning in young adults

BACKGROUND

Tobacco smoking represents a considerable public health burden globally. Smoking in older adults is associated with cognitive impairment and more rapid age-associated cognitive decline, but there is a paucity of studies in younger people.

METHOD

Adults aged 18-29 years were recruited from a longitudinal study investigating impulsivity in young people. Exclusion criteria were presence of any axis-I morbidity or cannabis use. Subjects undertook neurocognitive assessment using the Cambridge Neuropsychological Test Automated Battery (CANTAB). Demographic, clinical, and cognitive differences between smokers (N = 37) and nonsmokers (N = 177) were characterized.

RESULTS

Groups were well matched in terms of age, education, income, and gender. In comparison to nonsmokers, nicotine users showed significant cognitive impairments on sustained attention (target detection: p= .005), spatial working memory (errors: p= .023, strategy use: p= .004), executive planning (p= .002), and did not appropriately adjust behavior as a function of risk (Gamble task risk adjustment: p= .004). Smokers were intact on general response speeds and response inhibition.

CONCLUSIONS

These data, using objective translational paradigms, support an association between tobacco smoking and cognitive problems in young people, with implications for such individuals and for society. Future studies should extend these results longitudinally to explore causality, and evaluate effects of nicotinic agents (including anti-smoking medications) on cognition.

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.

Blood pressure, smoking and alcohol use, association with vascular dementia

The success of the ageing global population brings with it a growth in the number of dementia sufferers. Older adults are at highest risk of dementia and are likely to manifest both vascular and Alzheimer's pathology. Blood pressure also changes with ageing and there is evidence linking high blood pressure in midlife to an increased risk of later dementia. Data from later life is sparser. A number of intervention trials have been carried out with antihypertensives and have shown mixed results with regard to cognitive and dementia outcomes (both dementia overall and of vascular and Alzheimer's types). Meta-analyses have in general not found an association between blood pressure lowering and reduced dementia incidence, although the number of cases reported in the placebo controlled trials is invariably lower in the actively treated group. Systematic reviews and meta-analyses have also been published with regard to smoking and alcohol use and incident dementia. Despite mixed reports, overall smoking was associated with an increased risk of later dementia and alcohol with a 'U' or 'J' shaped relationship. Following the systematic reviews subsequent publications tend to report similar findings. The literature in this area suffers from differing populations, lengths of follow up and assessments of both risk factor and outcome. However, at present, maintenance of cognitive function would seem to be best served by treating cardiovascular risk factors in accordance with current guidelines, controlling blood pressure, reducing smoking and if consuming alcohol doing so in moderation. This review will concentrate on the prevention of dementia and attempt to provide an overview of the evidence relating to vascular related dementia and the potential risk factors of hypertension, alcohol use and smoking behaviour.

Immigrant status and cognitive functioning in late-life: an examination of gender variations in the healthy immigrant effect

Although some research suggests that the healthy immigrant effect extends to cognitive functioning, it is unclear whether this general pattern varies according to gender. We use six waves of data collected from the original cohort of the Hispanic Established Populations for the Epidemiologic Study of the Elderly to estimate a series of linear growth curve models to assess variations in cognitive functioning trajectories by nativity status and age at migration to the U.S.A. among women and men. Our results show, among women and men, no differences in baseline cognitive status (intercepts) between early- (before age 20) and late-life (50 and older) immigrants and U.S.-born individuals of Mexican-origin. We also find, among women and men, that middle-life (between the ages of 20 and 49) immigrants tend to exhibit higher levels of baseline cognitive functioning than the U.S.-born. Our growth curve analyses suggest that the cognitive functioning trajectories (slopes) of women do not vary according to nativity status and age at migration. The cognitive functioning trajectories of early- and late-life immigrant men are also similar to those of U.S.-born men; however, those men who migrated in middle-life tend to exhibit slower rates of cognitive decline. A statistically significant interaction term suggests that the pattern for middle-life migration is more pronounced for men (or attenuated for women). In other words, although women and men who migrated in middle-life exhibit higher levels of baseline cognitive functioning, immigrant men tend to maintain this advantage for a longer period of time. Taken together, these patterns confirm that gender is an important conditioning factor in the association between immigrant status and cognitive functioning.

Relation of secondhand smoking to mild cognitive impairment in older inpatients

Up to now, controversy still exists regarding the role of secondhand smoking (SHS) in developing cognitive impairment. This study aimed to evaluate the prevalence of SHS in hospitalized older patients with cognitive deficit, particularly in those with mild cognitive impairment (MCI). Smoking history was classified into four groups: never smokers, former-active smokers/no SHS, active smokers, and secondhand smokers, and cognitive function into three levels: normal cognition (C), MCI, and dementia. A total of 933 older subjects with diagnoses of MCI (n = 98), dementia (n = 124), or C (n = 711) were enrolled in this cross-sectional study. As expected, patients with dementia had significantly higher frequency of former-active smokers than cognitively normal. Moreover, patients with MCI showed a significantly higher frequency of active and secondhand smokers than patients with dementia or C. A smoking history is very frequent in older patients with dementia. Patients with MCI had even higher rate of exposure to active or secondhand smoking.

A prospective cohort study of long-term cognitive changes in older Medicare beneficiaries

Background

Promoting cognitive health and preventing its decline are longstanding public health goals, but long-term changes in cognitive function are not well-documented. Therefore, we first examined long-term changes in cognitive function among older Medicare beneficiaries in the Survey on Assets and Health Dynamics among the Oldest Old (AHEAD), and then we identified the risk factors associated with those changes in cognitive function.

Methods

We conducted a secondary analysis of a prospective, population-based cohort using baseline (1993-1994) interview data linked to 1993-2007 Medicare claims to examine cognitive function at the final follow-up interview which occurred between 1995-1996 and 2006-2007. Besides traditional risk factors (i.e., aging, age, race, and education) and adjustment for baseline cognitive function, we considered the reason for censoring (entrance into managed care or death), and post-baseline continuity of care and major health shocks (hospital episodes). Residual change score multiple linear regression analysis was used to predict cognitive function at the final follow-up using data from telephone interviews among 3,021 to 4,251 (sample size varied by cognitive outcome) baseline community-dwelling self-respondents that were ≥ 70 years old, not in managed Medicare, and had at least one follow-up interview as self-respondents. Cognitive function was assessed using the 7-item Telephone Interview for Cognitive Status (TICS-7; general mental status), and the 10-item immediate and delayed (episodic memory) word recall tests.

Results

Mean changes in the number of correct responses on the TICS-7, and 10-item immediate and delayed word recall tests were -0.33, -0.75, and -0.78, with 43.6%, 54.9%, and 52.3% declining and 25.4%, 20.8%, and 22.9% unchanged. The main and most consistent risks for declining cognitive function were the baseline values of cognitive function (reflecting substantial regression to the mean), aging (a strong linear pattern of increased decline associated with greater aging, but with diminishing marginal returns), older age at baseline, dying before the end of the study period, lower education, and minority status.

Conclusions

In addition to aging, age, minority status, and low education, substantial and differential risks for cognitive change were associated with sooner vs. later subsequent death that help to clarify the terminal drop hypothesis. No readily modifiable protective factors were identified.

Do executive function deficits predict later substance use disorders among adolescents and young adults?

OBJECTIVE

There is increasing interest regarding the risk and overlap of executive function deficits (EFDs) in stable cigarette smoking and substance use disorders (SUD). Therefore, we examined whether earlier EFD was a risk factor for subsequent cigarette smoking and SUD and further explored the relationship between EFD and SUD.

METHOD

We assessed 435 subjects at the 5-year follow-up (232 subjects with attention-deficit/hyperactivity disorder [ADHD], mean age ± SD: 15.4 ± 3.43 years; and 203 controls: 16.3 ± 3.42 years) and again 4 to 5 years later as part of a prospective family study of youth with ADHD. Individuals were assessed by structured psychiatric interview for psychopathology and SUD. EFD was categorically defined in an individual who had abnormal results on at least two of six neuropsychological tests of executive functioning.

RESULTS

At the final follow-up period, ADHD was found to be a significant predictor of stable cigarette smoking (p < .01) and SUD into late adolescence and young adult years (p < .01). However, EFDs were not associated with an increase in subsequent substance use outcomes. New-onset stable cigarette smoking, but not SUD, was associated with subsequent EFD (p < .01).

CONCLUSIONS

Our results do not support the hypothesis that EFDs predicts later stable cigarette smoking or SUD in children with ADHD growing up. However, stable cigarette smoking is associated with subsequent EFD.