The Effect of Undiagnosed Diabetes on the Association Between Self-Reported Diabetes and Cognitive Impairment Among Older Mexican Adults

The impact of diabetes in cognitive impairment: A review of current evidence and prospects for future investigations

Cognitive impairment in individuals with diabetes represents a multifaceted and increasingly prevalent health concern. This review critically examines the current evidence regarding the intricate relationship between diabetes and cognitive decline. It highlights the existing knowledge on the impact of diabetes on cognitive function, spanning from mild cognitive impairment to dementia, including vascular and Alzheimer dementia. The review underscores the need for a standardized diagnostic paradigm and explores research gaps, such as the implications of cognitive impairment in younger populations and various diabetes types. Furthermore, this review emphasizes the relevance of diabetes-related comorbidities, including hypertension and dyslipidemia, in influencing cognitive decline. It advocates for a comprehensive, interdisciplinary approach, integrating insights from neuroscience, endocrinology, and immunology to elucidate the mechanistic underpinnings of diabetes-related cognitive impairment. The second part of this review outlines prospective research directions and opportunities. It advocates for longitudinal studies to understand disease progression better and identifies critical windows of vulnerability. The search for accurate biomarkers and predictive factors is paramount, encompassing genetic and epigenetic considerations. Personalized approaches and tailored interventions are essential in addressing the substantial variability in cognitive outcomes among individuals with diabetes.

Differences in the Cognitive Function of Mexican Adults Aged 60 and Older with Self-Reported Diabetes in 2001 and 2018

BACKGROUND

The prevalence of type 2 diabetes in Mexico has nearly doubled for adults aged ≥60. Increases in education and healthcare resources to manage chronic conditions have contributed to population-level increases in the cognitive functioning of older adults. However, research has not focused on older adults with chronic conditions such as diabetes.

OBJECTIVE

Our objective was to compare the cognitive functioning of Mexican adults aged ≥60 with diabetes in 2001 and 2018.

METHODS

Data came from Mexican Health and Aging Study. Our study used a cross-sectional design and included participants aged ≥60 with self-reported diabetes during the 2001 (n = 1,052, mean age = 68.4, female = 59.6%) and 2018 (n = 2,469, mean age = 70.6, female = 62.0%) observation waves. Five cognitive tests were used to create a score of global cognition. Generalized estimating equations were used to compare global cognition in 2001 to 2018.

RESULTS

Older adults in 2018 had more education and were more likely than older adults in 2001 to take oral medication for diabetes, insulin, and to check blood sugar weekly. Older adults in 2018 had higher global cognition than in 2001 when adjusting for age, gender, education, and health insurance coverage (b = 0.38, SE = 0.02). This statistically significant difference remained after adjusting for health conditions, health behaviors, and diabetes management behaviors.

CONCLUSIONS

Older adults in Mexico with self-reported diabetes in 2018 had higher cognitive function than in 2001. Future research is needed to investigate causes of the cohort differences in cognitive functioning among Mexican older adults with self-reported diabetes.

Association Between Social Participation and Cognitive Function in Community-Dwelling Adults

Social participation is associated with cognitive function; however, their causal relationships have not been reported yet. This study was designed to examine the autoregressive effects and bidirectional causal relationship between social participation and cognitive function. In this secondary longitudinal data analysis, we enrolled 4,834 Korean adults. A cross-lagged panel model with fixed effects was used to examine the causal relationships between social participation and cognitive function. Both participation (unstandardized coefficient = .370, p < .001) and cognitive function (unstandardized coefficient = .151, p < .001) had positive autoregressive effects over time. Participation had a cross-lagged effect on cognitive function (unstandardized coefficient = .061, p < .001). However, the cross-lagged effects of cognitive function on participation were not statistically significant (unstandardized coefficient = .051, p = .312). Various health-care programs that promote social participation and improve cognitive function must be established. Additional studies are required to confirm the causal effects of cognitive function on participation.

The association between undiagnosed diabetes and cognitive function: findings from the China health and retirement longitudinal study

BACKGROUND

The cognitive function of people with diabetes has gained an increasing interest in recent years, and this study focuses on exploring the relationship between undiagnosed diabetes and cognitive function among the middle-aged and elderly people in China.

METHODS

The data came from the China Health and Retirement Longitudinal Study (CHARLS) which was conducted between July and October 2015. 9855 subjects were enrolled in the study. Executive function and episodic memory were used to assess cognitive function. The subjects were divided into three groups: no diabetes, diagnosed diabetes, and undiagnosed diabetes, and weighted multiple linear regression models were established to evaluate the association of undiagnosed diabetes with cognitive function.

RESULTS

After controlling for covariates, undiagnosed diabetes was statistically associated with executive function (β = -0.215, P < 0.01). In the age group of ≥65 years, undiagnosed diabetes was statistically associated with executive function (β = -0.358, P < 0.01) and episodic memory (β = -0.356, P < 0.01). When adjusting for confounders, no statistically significant associations were found between diagnosed diabetes and cognitive function except in 45-54 age group (β = 0.374, P < 0.05).

CONCLUSIONS

The cross-sectional study suggested that undiagnosed diabetes was linked to poor cognitive function, especially in the elderly population. Timely diagnosis and active treatment of diabetes are important to reduce the occurrence of cognitive impairment. Further prospective cohort studies are required to articulate the association between undiagnosed diabetes and cognitive function.

Social, behavioural, and functional characteristics of community-dwelling South Korean adults with moderate and severe cognitive impairment

OBJECTIVES

This study used the 2016 Korean Longitudinal Study on Aging to investigate the social, behavioural, and functional characteristics of community-dwelling South Korean adults with cognitive impairment.

METHODS

Participants were classified as normal, moderate impairment, and severe impairment according to an algorithm that combined the Korean Mini-Mental State Examination score and the number of difficulties in performing instrumental activities of daily living. Selected characteristics included grip strength, depression, participation in exercise and social activities, and living in a rural, urban, or suburban community.

RESULTS

Most (72.7%) participants were classified as having normal cognition, 20.1% were classified as moderate impairment, and 7.2% were classified as severe impairment. Regardless of sex, the differences in grip strength across the cognitive status classifications were statistically significant, except for the difference between moderate and severe cognitive impairment in males (p = 0.8477). Greater number of depressive symptoms and living in rural areas were associated with significantly higher odds for severe cognitive impairment. Participants with moderate (OR = 0.51) and severe (OR = 0.33) cognitive impairment were less likely to participate in social activities than those with normal cognition.

CONCLUSIONS

The study findings revealed that social, behavioural, and functional characteristics are closely related to the cognitive status of community-dwelling adults in South Korea.

Midlife Vascular Factors and Prevalence of Mild Cognitive Impairment in Late-Life in Mexico

OBJECTIVE

To estimate the prevalence of mild cognitive impairment (MCI) and its subtypes and investigate the impact of midlife cardiovascular risk factors on late-life MCI among the aging Mexican population.

METHOD

Analyses included a sample of non-demented adults over the age of 55 living in both urban and rural areas of Mexico (N = 1807). MCI diagnosis was assigned based on a comprehensive cognitive assessment assessing the domains of memory, executive functioning, language, and visuospatial ability. The normative sample was selected by means of the robust norms approach. Cognitive impairment was defined by a 1.5-SD cut-off per cognitive domain using normative corrections for age, years of education, and sex. Risk factors included age, education, sex, rurality, depression, insurance status, workforce status, hypertension, diabetes, stroke, and heart disease.

RESULTS

The prevalence of amnestic MCI was 5.9%. Other MCI subtypes ranged from 4.2% to 7.7%. MCI with and without memory impairment was associated with older age (OR = 1.01 [1.01, 1.05]; OR = 1.03 [1.01, 1.04], respectively) and residing in rural areas (OR = 1.49 [1.08, 2.06]; OR = 1.35 [1.03, 1.77], respectively). Depression (OR = 1.07 [1.02, 1.12]), diabetes (OR = 1.37 [1.03, 1.82]), and years of education (OR = 0.94 [0.91, 0.97]) were associated with MCI without memory impairment. Midlife CVD increased the odds of MCI in late-life (OR = 1.76 [1.19, 2.59], which was driven by both midlife hypertension and diabetes (OR = 1.70 [1.18, 2.44]; OR = 1.88 [1.19, 2.97], respectively).

CONCLUSIONS

Older age, depression, low education, rurality, and midlife hypertension and diabetes were associated with higher risk of late-life MCI among older adults in Mexico. Our findings suggest that the causes of cognitive impairment are multifactorial and vary by MCI subtype.

Effects of diabetes and obesity on cognitive impairment and mortality in older mexicans

BACKGROUND

Diabetes is a risk factor for dementia and mortality, while obesity later in life is associated with a reduced risk. Their co-occurrence, diabesity, is common, but its association with dementia and mortality is unclear.

METHODS

Using data from the Mexican Health and Aging Study, we used multinomial logistic regression to examine the associations of diabetes and body mass index (BMI), and diabesity, in 2012, with cognitive impairment and mortality in 2018, among participants aged ≥60 years with normal cognition at baseline (n = 7,885).

RESULTS

Diabetes was associated with cognitive impairment, compared to not having diabetes (RRR=1.83, 95% CI=1.48-2.26). BMI was not associated with cognitive impairment. Regarding mortality, diabetes was associated with an increased risk (RRR=2.28, 95% CI=1.98-2.63) and being overweight or having obesity was associated with a reduced risk (RRR=0.74, 95% CI=0.65-0.86; RRR=0.79, 95% CI= 0.66-0.95). When BMI and diabetes were combined, having diabetes only (RRR=2.01, 95% CI=1.40-2.87), being overweight with diabetes (RRR=1.42, 95% CI=1.02-1.97) or having diabesity (RRR=1.50, 95% CI=1.08-2.06) were associated with cognitive impairment, compared to having a normal BMI without diabetes. Diabetes, regardless of BMI, was associated with an increased risk of mortality, while being overweight or having obesity was associated with a reduced risk of mortality.

CONCLUSIONS

With the increase in the prevalence of obesity and diabetes among Mexicans, it is important to understand how these conditions and their co-occurrence impact cognitive impairment and mortality. Among older Mexicans, diabesity is associated with 6-year mortality and cognitive impairment onset, likely driven by the effect of diabetes.

Effect of Demographic and Health Dynamics on Cognitive Status in Mexico between 2001 and 2015: Evidence from the Mexican Health and Aging Study

Sources of health disparities such as educational attainment, cardiovascular risk factors, and access to health care affect cognitive impairment among older adults. To examine the extent to which these counteracting changes affect cognitive aging over time among Mexican older adults, we examine how sociodemographic factors, cardiovascular diseases, and their treatment relate to changes in cognitive function of Mexican adults aged 60 and older between 2001 and 2015. Self and proxy respondents were classified as dementia, cognitive impairment no dementia (CIND), and normal cognition. We use logistic regression models to examine the trends in dementia and CIND for men and women aged 60 years or older using pooled national samples of 6822 individuals in 2001 and 10,219 in 2015, and sociodemographic and health variables as covariates. We found higher likelihood of dementia and a lower risk of CIND in 2015 compared to 2001. These results remain after adjusting for sociodemographic factors, cardiovascular diseases, and their treatment. The improvements in educational attainment, treatment of diabetes and hypertension, and better access to health care in 2015 compared to 2001 may not have been enough to counteract the combined effects of aging, rural residence disadvantage, and higher risks of cardiovascular disease among older Mexican adults.

Does undiagnosed diabetes mitigate the association between diabetes and cognitive impairment? Findings from the ELSI-Brazil study

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with cognitive impairment. However, most of the evidence has been based on self-reported T2DM, and undiagnosed diabetes has not been considered as a separate category. We aimed to examine the extent to which undiagnosed diabetes modifies the association between diabetes and cognitive impairment in a representative sample of Brazilian adults aged 50 years and older.

METHODS

We analyzed baseline data from 1944 participants of the Brazilian Longitudinal Study of Aging (ELSI-Brazil) conducted from 2015 to 2016. Diabetes was evaluated based on self-reported doctor diagnosis and glycosylated hemoglobin levels. Participants were classified as diabetics (D), undiagnosed diabetics (UDD), or nondiabetics (ND). Cognitive function was assessed by word list learning and verbal fluency tests. Three multiple logistic regression models were used to evaluate the changes in the strength of the associations.

RESULTS

Participants with diabetes had 49% greater odds of exhibiting impaired memory than nondiabetics (odds ratio [OR] = 1.49; 95% CI: 1.01-2.20). By combining UDD and ND, the association between diabetes and impaired memory was attenuated by 2.0%, losing its statistical significance (OR = 1.46; 95% CI: 0.98-2.17). By combining UDD and D, the association was attenuated by 7.4% (OR = 1.38; 95% CI: 1.01-1.90). No significant association was found between T2DM and impaired verbal fluency.

CONCLUSION

This study found an association between T2DM and impaired memory but not with impaired verbal fluency. When UDD individuals are considered diabetics, this association is attenuated; when UDD individuals are considered as ND, this association is attenuated to the extent that it loses its statistical significance, affecting thus the clinical interpretation.

Decreased Levels of Serum IGF-1 and Vitamin D Are Associated With Cognitive Impairment in Patients With Type 2 Diabetes

PURPOSE

To determine the association of serum insulin-like growth factor 1 (IGF-1) and vitamin D levels with cognition status in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 173 patients with T2DM were recruited and divided into mild cognitive impairment (MCI) group (n = 94) and normal cognition (NC) group (n = 79). Levels of IGF-1 and 25(OH)D were measured and compared, and the correlations among IGF-1, 25(OH)D, and cognitive function were analyzed.

RESULTS

Insulin-like growth factor 1 and 25(OH)D levels significantly decreased in MCI group than those in the NC group (both P < .001). Multiple stepwise regression analysis revealed that IGF-1 (β = .146, P < .001) and 25(OH)D (β = .199, P < .001) independently predicted Montreal Cognitive Assessment (MoCA) scores. Partial least square regression showed that contributions of both 25(OH)D (P < .001) and IGF-1 (P < .001) to MoCA scores were significant, while no cross-effect was observed between them (P = .714).

CONCLUSIONS

Low serum IGF-1 and 25(OH)D levels may separately predict poor cognitive performance in patients with diabetes.

Association of Hypoglycemia With Subsequent Dementia in Older Patients With Type 2 Diabetes Mellitus

Background

Studies have found conflicting evidence regarding the association of hypoglycemia with dementia. We evaluated an association of hypoglycemia with subsequent dementia in patients with type 2 diabetes.

Methods

This retrospective longitudinal cohort study used the Clinical Practice Research Datalink, an electronic medical records data from the United Kingdom, from 2003 to 2012. We included patients aged >65 years diagnosed with type 2 diabetes, with no prior diagnosis of dementia. Dementia was defined using diagnosis codes from medical records. All patients were followed from the date of initial diabetes diagnosis. To account for competing risk of death, we used Fine and Gray's competing risk model to determine the association of hypoglycemia with dementia while adjusting for potential confounders. Hypoglycemia was modeled as a time-dependent covariate.

Results

Of 53,055 patients, 5.7% (n = 3,018) had at least one hypoglycemia episodes. The overall incidence rate of dementia was 12.7 per 1,000 person-years. In the fully adjusted model that controlled for all confounders, the occurrence of at least one hypoglycemia episode was associated with 27% higher odds of subsequent dementia (hazard ratio = 1.27; 95% confidence interval = 1.06-1.51). The risk increased with the number of hypoglycemia episodes: one episode (hazard ratio = 1.26; 95% confidence interval = 1.03-1.54); two or more episodes (hazard ratio = 1.50; 95% confidence interval = 1.09-2.08).

Conclusions

Hypoglycemia is associated with a higher risk of dementia and may be responsible in part for the higher risk of dementia in patients with diabetes. Alternatively, hypoglycemia may be a marker for undiagnosed cognitive impairment, and we cannot rule out the possibility of reverse causation between hypoglycemia and dementia.