Smoking and Cognitive Function Among Middle-Aged Adults in China: Findings From the China Health and Retirement Longitudinal Study Baseline Survey

The relationship between healthy lifestyles and cognitive function in Chinese older adults: the mediating effect of depressive symptoms

BACKGROUND

Previous studies have proven the positive relationship between healthy lifestyles and cognitive function in older adults. However, the specific impacts and mechanisms require further investigation. Therefore, this study aimed to investigate whether healthy lifestyles and cognitive function were associated with Chinese older adults and whether depressive symptoms mediated their association.

METHODS

8272 valid samples were included using the latest data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Pearson's test was applied to investigate the relationship between the key variables. Regression models were employed to examine the mediating effects of healthy lifestyles, using Sobel's test and the bootstrap method to confirm path effects.

RESULTS

There was a significant correlation between healthy lifestyles, depressive symptoms, and cognitive function (p < 0.01). Healthy lifestyles directly impact cognitive function (β = 0.162, p < 0.01). Healthy lifestyles had a significant effect on depressive symptoms (β=-0.301, p < 0.01), while depressive symptoms have a significant impact on cognitive function (β=-0.108, p < 0.01). Depressive symptoms partially mediated the effect of healthy lifestyles on cognitive function (β = 0.032, p < 0.01). The Sobel and bootstrap tests confirmed the robustness of the regression analysis results.

CONCLUSION

Depressive symptoms mediate the relationship between healthy lifestyles and cognitive function. Our findings suggest that prevention strategies for cognitive impairment in older adults should focus on healthy lifestyles and mental health.

Risk assessment and stratification of mild cognitive impairment among the Chinese elderly: attention to modifiable risk factors

BACKGROUND

The early identification of individuals at risk of mild cognitive impairment (MCI) has major public health implications for Alzheimer's disease prevention.

OBJECTIVE

This study aims to develop and validate a risk assessment tool for MCI with a focus on modifiable factors and a suggested risk stratification strategy.

METHODS

Modifiable risk factors were selected from recent reviews, and risk scores were obtained from the literature or calculated based on the Rothman-Keller model. Simulated data of 10 000 subjects with the exposure rates of the selected factors were generated, and the risk stratifications were determined by the theoretical incidences of MCI. The performance of the tool was verified using cross-sectional and longitudinal datasets from a population-based Chinese elderly cohort.

RESULTS

Nine modifiable risk factors (social isolation, less education, hypertension, hyperlipidaemia, diabetes, smoking, drinking, physical inactivity and depression) were selected for the predictive model. The area under the curve (AUC) was 0.71 in the training set and 0.72 in the validation set for the cross-sectional dataset. The AUCs were 0.70 and 0.64 in the training and validation sets, respectively, for the longitudinal dataset. A combined risk score of 0.95 and 1.86 was used as the threshold to categorise MCI risk as 'low', 'moderate' and 'high'.

CONCLUSION

A risk assessment tool for MCI with appropriate accuracy was developed in this study, and risk stratification thresholds were also suggested. The tool might have significant public health implications for the primary prevention of MCI in elderly individuals in China.

Urinary tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and cognitive functioning in older adults: The National Health and Nutrition Examination Survey 2013-2014

INTRODUCTION

Tobacco contains carcinogens called tobacco-specific nitrosamines. Among the tobacco-specific nitrosamines, is nicotine-derived nitrosamine ketone (NNK) which produces the metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). We aimed to examine the association between urinary tobacco-specific NNAL and cognitive functioning among older adults.

METHODS

A total of 1673 older adults aged ≥60 years from the National Health and Nutrition Examination Survey 2013-2014 were included. Urinary tobacco-specific NNAL was analyzed in the laboratory. Cognitive functioning was measured using the Consortium to Establish a Registry for Alzheimer's Disease Word Learning subtest (CERAD-WL) immediate and delayed memory tests, the Animal Fluency test (AFT), and the Digit Symbol Substitution Test (DSST). Test-specific and global cognition z-scores were calculated based on means and standard deviations of the cognitive test scores. Multivariable linear regression models were constructed to examine the independent association between quartiles of urinary tobacco-specific NNAL and cognitive test-specific and global cognition z-scores controlling for age, sex, race/ethnicity, education level, depressive symptoms, body mass index, systolic blood pressure, urinary creatinine, hypertension, diabetes, alcohol use, and smoking status.

RESULTS

About half of the participants (mean age 69.8 years) were female (52.1%), non-Hispanic White (48.3%), and completed some college and above (49.7%). Multivariable linear regression results showed that participants in the 4th quartile (highest quartile) of urinary NNAL, compared with those in the 1st quartile (lowest quartile), had lower DSST z-scores (β= -0.19; 95% CI: -0.34 - -0.04).

CONCLUSIONS

Tobacco-specific NNAL was negatively associated with processing speed, sustained attention, and working memory in older adults.

Mendelian randomization analyses of smoking and Alzheimer's disease in Chinese and Japanese populations

Background

Previous epidemiological studies have reported controversial results on the relationship between smoking and Alzheimer's disease (AD). Therefore, we sought to assess the association using Mendelian randomization (MR) analysis.

Methods

We used single nucleotide polymorphisms (SNPs) associated with smoking quantity (cigarettes per day, CPD) from genome-wide association studies (GWAS) of Japanese population as instrumental variables, then we performed two-sample MR analysis to investigate the association between smoking and AD in a Chinese cohort (1,000 AD cases and 500 controls) and a Japanese cohort (3,962 AD cases and 4,074 controls), respectively.

Results

Genetically higher smoking quantity showed no statistical causal association with AD risk (the inverse variance weighted (IVW) estimate in the Chinese cohort: odds ratio (OR) = 0.510, 95% confidence interval (CI) = 0.149-1.744, p = 0.284; IVW estimate in the Japanese cohort: OR = 1.170, 95% confidence interval CI = 0.790-1.734, p = 0.434).

Conclusion

This MR study, for the first time in Chinese and Japanese populations, found no significant association between smoking and AD.

Frailty is associated with worse cognitive functioning in older adults

INTRODUCTION

Frailty and impaired cognitive functioning often co-occur in older adults and are associated with adverse health outcomes. However, their relationship is unclear. This study sought to examine the association of frailty status with cognitive functioning in older adults.

METHOD

The study population consisted of 2,296 older adults aged ≥60 from the National Health and Nutrition Examination Survey 2011-2014. Frailty status was measured based on the Fried Phenotype and the participants were categorized into three groups- robust, pre-frailty, and frailty. Cognitive functioning was measured using the Consortium to Establish a Registry for Alzheimer's Disease Word Learning subtest (CERAD-WL) immediate and delayed recall tests, the Animal Fluency test (AFT), and the Digit Symbol Substitution Test (DSST). Test-specific and global cognition z-scores were calculated. Multinomial linear regression models were constructed to examine the association between frailty status (reference: robust) and test-specific and global cognition z-scores. Multiple linear regression models were used to examine the relationship between the number of frailty dimensions and test-specific and global cognition z-scores. All models controlled for age, race/ethnicity, education, total cholesterol level, and systolic blood pressure.

RESULTS

About half of the participants (median age 68 years) were female (49.9%) and non-Hispanic White (48.7%). A quarter (23.3%) of the participants completed some college and above. Multinominal linear regression showed that compared with participants who were robust, those with frailty had worse DSST [β = -0.234, 95% confidence interval (CI): -0.391, -0.078, P = 0.003] and global cognition z scores (β = -0.129, 95% CI -0.233, -0.025, P = 0.02). Multiple linear regression model showed that the number of frailty dimensions was significantly associated with decreased the DSST (β = -0.065, 95% CI -0.103, -0.026, P = 0.001) and global cognition z-scores (β= -0.034, 95% CI -0.06, -0.009, P = 0.009).

CONCLUSION

Frailty is associated with worse processing speed, sustained attention, working memory, and global cognition in older adults. Prevention and treatment of frailty in older adults may help protect their cognitive functioning. Further, clinicians should consider assessing cognitive functioning, especially processing speed, sustained attention, and working memory, among frail older patients, which may allow early identification and interventions of cognitive impairment.

Concurrent serum lead levels and cognitive function in older adults

Introduction

In this study, we investigated the relationship between serum lead levels and cognitive functioning in a sample of older adults in the US.

Method

Using the National Health and Nutrition Examination Survey (NHANES) 2011-2013, a total of 768 older adults aged ≥60 years were included in the analysis. Lead concentrations in the whole blood samples were assessed using mass spectrometry. We used the immediate and delayed memory portions of the Consortium to Establish a Registry for Alzheimer's Disease Word Learning Subtest (CERAD-WL), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST) to assess the participants' cognitive performance. Using sample averages and standard deviations (SDs), we computed test-specific and global cognition z-scores. To assess the relationships between the quartiles of serum lead levels and cognitive performance, we built multiple linear regression models and adjusted for covariates, including age, sex, race/ethnicity, education, depressive symptoms, alcohol usage, and body mass index.

Results

The average age of the participants was 69.6 (SD 6.6) years. Approximately half of the participants were women (52.6%), non-Hispanic white (52.0%), and had completed at least some college education (51.8%). The average serum lead concentration was 1.8 g/dL (SD 1.6) for these participants. The results of multiple linear regression using individuals in the lowest serum lead quantile as a reference group revealed that the serum lead level was not associated with test-specific (CERAD-WL, AFT, and DSST) or global cognitive z-scores.

Conclusions

In older adults, concurrent serum lead concentration is not related to cognitive performance. Early or continuous lead exposure may exert a greater effect on the etiology of accelerated cognitive decline with old age.

Effect modification by aging on the associations of nicotine exposure with cognitive impairment among Chinese elderly

Active and passive exposure to tobacco smoke may increase risk of cognitive decline. However, effects of enhanced the aging process on the association of urinary nicotine metabolites with cognitive impairment remain unclear. In this study, 6657 Chinese older adults completed the physical examinations and cognitive tests. We measured urinary nicotine metabolite levels, mitochondrial DNA copy number (mtDNA-CN), and relative telomere length (RTL) and analyzed effects of urinary nicotine metabolites and their interaction with mtDNA-CN or RTL on cognitive impairment by generalized linear models and qg-computation, respectively. Each 1-unit increase in urinary 3-OHCot, 3-OHCotGluc, CotGluc, or NicGluc levels corresponded to a 1.05-, 1.09-, 1.04-, and 0.90-fold increased risk of cognitive impairment. Each 1-quantile increment in the mixture level of 8 nicotine metabolites corresponded to an increment of 1.40- and 1.34-fold risk of cognitive impairment in individuals with longer RTL or low mtDNA-CN. Urinary 3-OHCotGluc and RTL or mtDNA-CN exhibited an additive effect on cognitive impairment in addition to the mixture of 8 nicotine metabolites and mtDNA-CN. The findings suggested that aging process may increase the risk of tobacco-related cognitive impairment.

Higher blood cotinine level is associated with worse cognitive functioning in non-smoking older adults

Introduction

Secondhand smoke (SHS) is common in older adults; however, its cognitive effect is unclear. We aimed to examine the association between serum cotinine level and cognitive functioning among non-smoking older adults.

Materials and methods

A total of 2,703 older adults aged 60 and above from the National Health and Nutrition Examination (NHANES) Survey 2011-2014 were included. Serum cotinine level was analyzed in the laboratory. A level ≤10 ng/ml and a response of "no" to the question "Do you currently smoke?" were used to select non-smokers. Cognitive functioning was measured using the Consortium to Establish a Registry for Alzheimer's disease Word Learning subtest (CERAD-WL) immediate and delayed recall tests, the Animal Fluency test (AFT), and the Digit Symbol Substitution test (DSST). Multivariable linear regression models were constructed to examine the association between serum cotinine level quartile and test-specific and global cognition z scores adjusting for age, race/ethnicity, education, depressive symptoms, body mass index, alcohol use, smoking history, prevalent coronary heart disease (CHD), stroke, and systolic blood pressure.

Results

About half of the participants (mean age 70.5 years) were female (53.6%), non-Hispanic White (48.3%), and completed some college and above (50.2%). Multivariate linear regressions with a reference group being those in the 1st quantile (lowest) showed that participants in the 4th quartile (highest) of serum cotinine level had lower immediate recall [β = -0.16, 95% confidence interval (CI) = -0.29, -0.03], AFT (β = -0.19, 95% CI = -0.33, -0.05), DSST (β = -0.27, 95% CI = -0.39, -0.15), and global cognition (β = -0.26, 95% CI = -0.39, -0.14) z scores. Participants in the 3rd quartile had lower immediate recall (β = -0.16, 95% CI = -0.30, -0.02) and global cognition (β = -0.16, 95% CI = -0.29, -0.02) z scores. Participants in the 2nd quartile had lower delayed recall z scores (β = -0.16, 95% CI = -0.29, -0.02).

Conclusion

Higher serum cotinine level was associated with worse cognitive functioning in non-smoking older adults. Prevention and reduction of SHS in older adults may help protect their cognitive functioning.

Secondhand smoke is positively associated with pre-frailty and frailty in non-smoking older adults

INTRODUCTION

Either exposure to secondhand smoke (SHS) or frailty has been linked to adverse health outcomes in nonsmoking adults. However, their relationship is rarely studied. The purpose of this study is to examine the association between serum cotinine level and frailty status among non-smoking older adults.

METHOD

The study population consisted of 2,703 older adults aged ≥60 from the National Health and Nutrition Examination Survey 2011-2014. Non-smokers were included based on (1) a serum cotinine level ≤ 10 ng/mL and 2) a response of "no" to the question, "Do you currently smoke?" Frailty status was measured based on the Fried Phenotype and had three groups- robust, pre-frailty, and frailty. Multinomial logistic regression models were constructed to examine the association between serum cotinine level quartile and frailty status, controlling for age, sex, race/ethnicity, education, depressive symptoms, alcohol use, and systolic blood pressure.

RESULTS

About half of the participants (median age 70.0 years, range 64-78) were female (53.6%), non-Hispanic White (48.3%), and completed some college and above (50.1%). Multinomial logistic regression with a reference group being those in the 1^st quantile (the lowest) of serum cotinine level showed that participants in the 4^th quartile (the highest) of serum cotinine level had increased odds of pre-frailty vs. robust (OR 1.522, 95% confidence interval [CI] 1.060, 2.185, P = 0.023) as well as increased odds of frailty vs. robust (OR 2.349, 95% CI 1.081, 5.107, P = 0.031).

CONCLUSIONS

Higher serum cotinine level is associated with increased risk of pre-frailty and frailty versus robust in non-smoking older adults. Prevention and reduction of SHS in older adults may help protect them from developing pre-frailty or frailty.

Trajectories of Multiple Behavioral Risk Factors and Their Associations With Cognitive Function Trajectories Among Older African Americans and White Americans

Objectives: This study examined the joint trajectories of behavioral risk factors (smoking, alcohol drinking, and body mass index) and their associations with cognitive function trajectories among older African Americans and white Americans. Methods: Data from the Health and Retirement Study (1998-2014) were used. Group-based mixture modeling and multinomial logistic regression analysis were performed. Results: Three joint trajectories of behavioral risk factors (overweight, smoking and drinking, and drinking and overweight) and three cognitive function trajectories (low, moderate, and high) were identified. A significantly higher percentage of African Americans were in the "overweight," "smoking and drinking," and "low" cognitive functioning groups as measured by the total cognition composite score compared to white Americans. After accounting for covariates, the "drinking and overweight" group was associated with the "moderate" or "high" cognitive functioning group. Discussion: Future interventions targeting the combinations of behavioral risk factors are needed to promote healthy aging among high-risk populations.