Exploring sex differences: insights into gene expression, neuroanatomy, neurochemistry, cognition, and pathology

Increased knowledge about sex differences is important for development of individualized treatments against many diseases as well as understanding behavioral and pathological differences. This review summarizes sex chromosome effects on gene expression, epigenetics, and hormones in relation to the brain. We explore neuroanatomy, neurochemistry, cognition, and brain pathology aiming to explain the current state of the art. While some domains exhibit strong differences, others reveal subtle differences whose overall significance warrants clarification. We hope that the current review increases awareness and serves as a basis for the planning of future studies that consider both sexes equally regarding similarities and differences.

Association Between Estimated Pulse Wave Velocity and Cognitive Performance in Older Black and White Adults in NHANES

BACKGROUND

Aging-associated cognitive decline is greater in non-Hispanic Black (NHB) adults than non-Hispanic White (NHW) adults. An important risk factor for cognitive decline with aging is arterial stiffening, though the importance to racial variation remains poorly understood.

OBJECTIVE

We examined the association of an estimate of arterial stiffness with cognitive function in a bi-racial sample of 60-85-year-old adults (N = 3,616, 26.5% NHB) enrolled in the National Health and Nutrition Examination Survey (NHANES) between 1999-2002 and 2011-2014.

METHODS

As a measure of vascular aging, pulse wave velocity was estimated (ePWV) using an equation incorporating age and mean arterial pressure and expressed as m/s. Using the digit symbol substitution test (DSST), cognitive function was expressed as the number of correctly matched symbols (out of 133) within 120 s. Linear regression models examined associations between ePWV and DSST.

RESULTS

In models that adjusted for sex, education, smoking, body mass index, history of cardiovascular disease, and hypertension, ePWV was inversely associated with DSST score in NHB adults (β= -3.47, 95% CI = -3.9 to -3.0; p <  0.001) and NHW adults (β= -3.51, 95% CI = -4.4 to -2.6; p <  0.001).

CONCLUSION

ePWV is inversely associated with a measure of cognitive function in older Black and White adults. ePWV may be a useful measure of vascular aging that can offer insight into cognitive aging.

Blood Pressure and Later-Life Cognition in Hispanic and White Adults (BP-COG): A Pooled Cohort Analysis of ARIC, CARDIA, CHS, FOS, MESA, and NOMAS

BACKGROUND

Ethnic differences in cognitive decline have been reported. Whether they can be explained by differences in systolic blood pressure (SBP) is uncertain.

OBJECTIVE

Determine whether cumulative mean SBP levels explain differences in cognitive decline between Hispanic and White individuals.

METHODS

Pooled cohort study of individual participant data from six cohorts (1971-2017). The present study reports results on SBP and cognition among Hispanic and White individuals. Outcomes were changes in global cognition (GC) (primary), executive function (EF) (secondary), and memory standardized as t-scores (mean [SD], 50 [10]); a 1-point difference represents a 0.1 SD difference in cognition. Median follow-up was 7.7 (Q1-Q3, 5.2-20.1) years.

RESULTS

We included 24,570 participants free of stroke and dementia: 2,475 Hispanic individuals (median age, cumulative mean SBP at first cognitive assessment, 67 years, 132.5 mmHg; 40.8% men) and 22,095 White individuals (60 years,134 mmHg; 47.3% men). Hispanic individuals had slower declines in GC, EF, and memory than White individuals when all six cohorts were examined. Two cohorts recruited Hispanic individuals by design. In a sensitivity analysis, Hispanic individuals in these cohorts had faster decline in GC, similar decline in EF, and slower decline in memory than White individuals. Higher time-varying cumulative mean SBP was associated with faster declines in GC, EF, and memory in all analyses. After adjusting for time-varying cumulative mean SBP, differences in cognitive slopes between Hispanic and White individuals did not change.

CONCLUSION

We found no evidence that cumulative mean SBP differences explained differences in cognitive decline between Hispanic and White individuals.

Differences in the prevalence of mental health disorders among Black American adults with sickle cell disease compared to those with non-heritable medical conditions or no medical conditions

Our aim was to determine differences in the prevalence of mental health disorders between Black Americans living with sickle cell disease (SCD) and Black Americans with other, non-heritable medical conditions, or no medical conditions. We examined the prevalence of mental health disorders among a non-institutionalized, community sample of Black adults in the US from the National Survey of American Life. We compared the odds of mental health disorders between Black American adults with SCD and those with other medical conditions, or no medical condition. Among the SCD group, 38·8% reported at least one mental health disorder: 17·6% endorsed a mood disorder, 24·7% an anxiety disorder, 2·4% an eating disorder, and 11·8% a childhood disorder. Compared to those with other medical conditions, Black Americans with SCD had greater poverty, more children in the household, and were less likely to be married/cohabitating (all P < 0·05). Yet, Black Americans with SCD were not at greater odds of having a mental health disorder compared to those with other medical conditions. When compared to the group with no conditions, however, individuals with SCD had 2·57 greater odds of mood disorder (95% confidence interval: 1·43-4·65; P = 0·002). The effect remained when controlling for socioeconomic status, marital status, and perceived physical health. In this study, almost 40% of Black American adults with SCD presented with a mental health disorder. Prevalence of mental health disorders was similar among those with non-heritable medical conditions, but those without a medical condition had a lower prevalence than in SCD. Among Black Americans, there appear to be unmeasured factors, common across medical conditions, that are linked to mental health disorders.

Racial and ethnic differences in medication use among beneficiaries of social security disability insurance with rheumatoid arthritis

OBJECTIVE

To determine racial/ethnic differences in the use of conventional synthetic or biologic disease-modifying anti-rheumatic drugs (csDMARDs or bDMARDs, respectively) and long-term glucocorticoids (GC) or opioids among beneficiaries of the Social Security Disability Insurance (SSDI) with rheumatoid arthritis (RA) and <65 years old.

METHODS

Serial cross-sectional analyses of Centers for Medicare and Medicaid Services claims data (2007, 2011, and 2014) for individuals <65 years old with RA receiving SSDI Medicare and Medicaid, no longer working because they were considered disabled. Generalized estimating equation models were used to determine whether the proportion of patients who used csDMARD, bDMARD, long-term GC, and long-term opioids differed by race/ethnicity.

RESULTS

There were 12,931; 15,033; and 15,599 participants in 2007, 2011, and 2014, respectively. The overall use of csDMARD without bDMARD among beneficiaries of the SSDI were 31.1%, 30.3%, and 29.2%; 50.2%, 51.7%, and 53.8% used bDMARDs; 37.6%, 36.1%, and 34.4% used long-term GC; and 61.1%, 63.8%, and 63.7% used long-term opioids in years 2007, 2011, and 2014 respectively. The use of csDMARDs without bDMARDs was higher and the use of bDMARDs was lower among Blacks compared to Whites (adjusted absolute difference: +3.0%, +5.0%, and +3.3% for csDMARDs without bDMARDs and -4.6%, -5.7%, and -4.0% for bDMARDs in 2007, 2011, and 2014, respectively; all p<0.05). The use of bDMARDs was higher among Hispanics compared to Whites (adjusted absolute difference: +7.1%, +7.3%, and +7.5% in 2007, 2011, and 2014, respectively; all p<0.05). Long-term GC use was lower among Hispanics than among Whites only in year 2014 (absolute percentage point difference of -4.2%); no other difference in long-term GC use was identified. Whites were the patients with the highest use of long-term opioids (more than two third in each calendar year).

CONCLUSION

Racial and ethnic differences exists in regards to the treatment of RA among beneficiaries of the SSDI. These findings suggest that this already vulnerable population of patients with RA can also have a racial and ethnic disparity that can contribute to additional disease burden and that should be examined in order to inform future interventions or even inform future policy changes to the SSDI.

Association Between Blood Pressure and Later-Life Cognition Among Black and White Individuals

Importance

Black individuals are more likely than white individuals to develop dementia. Whether higher blood pressure (BP) levels in black individuals explain differences between black and white individuals in dementia risk is uncertain.

Objective

To determine whether cumulative BP levels explain racial differences in cognitive decline.

Design, Setting, and Participants

Individual participant data from 5 cohorts (January 1971 to December 2017) were pooled from the Atherosclerosis Risk in Communities Study, Coronary Artery Risk Development in Young Adults Study, Cardiovascular Health Study, Framingham Offspring Study, and Northern Manhattan Study. Outcomes were standardized as t scores (mean [SD], 50 [10]); a 1-point difference represented a 0.1-SD difference in cognition. The median (interquartile range) follow-up was 12.4 (5.9-21.0) years. Analysis began September 2018.

Main Outcomes and Measures

The primary outcome was change in global cognition, and secondary outcomes were change in memory and executive function.

Exposures

Race (black vs white).

Results

Among 34 349 participants, 19 378 individuals who were free of stroke and dementia and had longitudinal BP, cognitive, and covariate data were included in the analysis. The mean (SD) age at first cognitive assessment was 59.8 (10.4) years and ranged from 5 to 95 years. Of 19 378 individuals, 10 724 (55.3%) were female and 15 526 (80.1%) were white. Compared with white individuals, black individuals had significantly faster declines in global cognition (-0.03 points per year faster [95% CI, -0.05 to -0.01]; P = .004) and memory (-0.08 points per year faster [95% CI, -0.11 to -0.06]; P < .001) but significantly slower declines in executive function (0.09 points per year slower [95% CI, 0.08-0.10]; P < .001). Time-dependent cumulative mean systolic BP level was associated with significantly faster declines in global cognition (-0.018 points per year faster per each 10-mm Hg increase [95% CI, -0.023 to -0.014]; P < .001), memory (-0.028 points per year faster per each 10-mm Hg increase [95% CI, -0.035 to -0.021]; P < .001), and executive function (-0.01 points per year faster per each 10-mm Hg increase [95% CI, -0.014 to -0.007]; P < .001). After adjusting for cumulative mean systolic BP, differences between black and white individuals in cognitive slopes were attenuated for global cognition (-0.01 points per year [95% CI, -0.03 to 0.01]; P = .56) and memory (-0.06 points per year [95% CI, -0.08 to -0.03]; P < .001) but not executive function (0.10 points per year [95% CI, 0.09-0.11]; P < .001).

Conclusions and Relevance

These results suggest that black individuals' higher cumulative BP levels may contribute to racial differences in later-life cognitive decline.

Blood Pressure and Cognitive Decline Over 8 Years in Middle-Aged and Older Black and White Americans

Although the association between high blood pressure (BP), particularly in midlife, and late-life dementia is known, less is known about variations by race and sex. In a prospective national study of 22 164 blacks and whites ≥45 years without baseline cognitive impairment or stroke from the REGARDS cohort study (Reasons for Geographic and Racial Differences in Stroke), enrolled 2003 to 2007 and followed through September 2015, we measured changes in cognition associated with baseline systolic and diastolic BP (SBP and DBP), as well as pulse pressure (PP) and mean arterial pressure, and we tested whether age, race, and sex modified the effects. Outcomes were global cognition (Six-Item Screener; primary outcome), new learning (Word List Learning), verbal memory (Word List Delayed Recall), and executive function (Animal Fluency Test). Median follow-up was 8.1 years. Significantly faster declines in global cognition were associated with higher SBP, lower DBP, and higher PP with increasing age ( P<0.001 for age×SBP×follow-up-time, age×DBP×follow-up-time, and age×PP×follow-up-time interaction). Declines in global cognition were not associated with mean arterial pressure after adjusting for PP. Blacks, compared with whites, had faster declines in global cognition associated with SBP ( P=0.02) and mean arterial pressure ( P=0.04). Men, compared with women, had faster declines in new learning associated with SBP ( P=0.04). BP was not associated with decline of verbal memory and executive function, after controlling for the effect of age on cognitive trajectories. Significantly faster declines in global cognition over 8 years were associated with higher SBP, lower DBP, and higher PP with increasing age. SBP-related cognitive declines were greater in blacks and men.

Sex/gender differences in cognition, neurophysiology, and neuroanatomy

In this mini-review, I summarize and interpret the current status of sex/gender differences in terms of brain anatomy, brain function, behavior, and cognition. Based on this review and the reported findings, I conclude that most of these sex/gender differences are not large enough to support the assumption of sexual dimorphism in terms of brain anatomy, brain function, cognition, and behavior. Instead, I suggest that many brain and cognitive features are modulated by environment, culture, and practice (and several other influences). These influences interact with the menstrual cycle, the general hormone level, and current gender stereotypes in a way that has not yet been fully understood.

Disparities in hypertension among black Caribbean populations: a scoping review by the U.S. Caribbean Alliance for Health Disparities Research Group (USCAHDR)

Background

Despite the large body of research on racial/ethnic disparities in health, there are limited data on health disparities in Caribbean-origin populations. This scoping review aimed to analyze and synthesize published and unpublished literature on the disparities in hypertension and its complications among Afro-Caribbean populations.

Methods

A comprehensive protocol, including a thorough search strategy, was developed and used to identify potentially relevant studies. Identified studies were then screened for eligibility using pre-specified inclusion/exclusion criteria. An extraction form was developed to chart data and collate study characteristics including methods and main findings. Charted information was tagged by disparity indicators and thematic analysis performed. Disparity indicators evaluated include ethnicity, sex, socioeconomic status, disability, sexual orientation and geographic location. Gaps in the literature were identified and extrapolated into a gap map.

Results

A total of 455 hypertension related records, published between 1972 and 2012, were identified and screened. Twenty-one studies met inclusion criteria for detailed analysis. The majority of studies were conducted in the United Kingdom and utilized a cross-sectional study design. Overall, studies reported a higher prevalence of hypertension among Caribbean blacks compared to West African blacks and Caucasians. Hypertension and its related complications were highest in persons with low socioeconomic status. Gap analysis showed limited research data reporting hypertension incidence by sex and socioeconomic status. No literature was found on disability status or sexual orientation as it relates to hypertension. Prevalence and morbidity were the most frequently reported outcomes.

Conclusion

The literature on hypertension health disparities in Caribbean origin populations is limited. Future research should address these knowledge gaps and develop approaches to reduce them.

Electronic supplementary material

The online version of this article (doi:10.1186/s12939-015-0229-0) contains supplementary material, which is available to authorized users.

Hypertension in the US Black population: risk factors, complications, and potential impact of central aortic pressure on effective treatment

PURPOSE

The identification of specific factors that contribute to hypertension development and progression among blacks in the US is the focus of much ongoing research. The purpose of this paper is to review these factors and discuss how they present unique opportunities for improving the management of hypertension in this difficult-to-treat population.

METHODS

We searched the published literature for articles discussing the risk factors for hypertension and cardiovascular disease in blacks; the target-organ damage and cardiovascular complications associated with hypertension in this difficult-to-treat population; and the role of central blood pressure in predicting cardiovascular events.

RESULTS

The prevalence of hypertension is higher in blacks than in other race/ethnic groups, with environmental and genetic risk factors likely playing an important role. The cardiovascular and renal consequences of hypertension (eg, left ventricular hypertrophy and renal failure) are also greater in blacks relative to their white counterparts. Preliminary data suggest that central blood pressure may be higher in blacks than in whites and has the potential for greater prognostic capability relative to peripheral blood pressure.

CONCLUSIONS

There is an urgent need to successfully control hypertension in the black population. Although data are limited in blacks, evidence suggests that central blood pressure warrants more continued assessment in future clinical studies.

White matter hyperintensity and cognitive functioning in the racial and ethnic minority cohort of the Framingham Heart Study

BACKGROUND

Previous studies have demonstrated an association between white matter hyperintensities (WMH) and cognitive performance primarily in Caucasian samples, limiting generalizability to other ethnic and racial groups. This study investigated the association of WMH and cognition in an ethnic and racial minority cohort (Omni) of the Framingham Heart Study and compared these results to the Caucasian (Offspring) cohort.

METHODS

Quantitative brain MRI and neuropsychological evaluations were performed on stroke- and dementia-free participants. Cognitive assessment included verbal memory, visuospatial memory and organization, language, and executive functioning. Linear regression models were conducted to assess the association between WMH and cognitive function.

RESULTS

The Omni group presented with demographic factors that significantly differed from those of the Offspring group: they were younger, but had more stroke risk factors such as hypertension. In the Offspring group, WMH volume was significantly associated with poorer performance on tests of executive function and visual organization. No significant associations between WMH and cognitive measures were found in the Omni group, but no differences (significant interaction terms) were seen between the regression coefficients.

CONCLUSIONS

The Omni cohort had greater variability in factors that may mediate the association of WMH and cognition. More research is needed to investigate how stroke risk factors impact on the occurrence of WMH and its association with cognition in more diverse cohorts.

Hypertension and dementia

Although hypertension is well known as a cause of vascular dementia (VaD), recent findings highlight the role of hypertension in the pathogenesis of Alzheimer's disease (AD) as well as mild cognitive impairment (MCI). Recent studies have shown that disruption of diurnal blood pressure (BP) variation is closely associated with cognitive impairment via injury of the small cerebral arteries indicating that long-standing hypertension constitutes a risk of brain matter atrophy or white matter lesions (WMLs). In several clinical trials, BP-lowering with antihypertensive agents was suggested to reduce the risk of dementia or cognitive decline. This review paper focuses on the role of hypertension as a risk factor for cognitive impairment, and summarizes current knowledge on the relationships between ambulatory BP monitoring (ABPM) and cognitive impairment. Finally, an overview of the impact of antihypertensive therapy on dementia prevention is provided.