Peripheral immune function and Alzheimer's disease: a living systematic review and critical appraisal.

BACKGROUND: A growing body of literature examines the relationship between peripheral immune function and Alzheimer's Disease (AD) in human populations. Our living systematic review summarizes the characteristics and findings of these studies, appraises their quality, and formulates recommendations for future research. METHODS: We searched the electronic databases PubMed, PsycINFO, and Web of Science, and reviewed references of previous reviews and meta-analyses to identify human studies examining the relationship between any peripheral immune biomarkers and AD up to September 7th, 2023. We examined patterns of reported statistical associations (positive, negative, and null) between each biomarker and AD across studies. Evidence for each biomarker was categorized into four groups based on the proportion of studies reporting different associations: corroborating a positive association with AD, a negative association, a null association, and presenting contradictory findings. A modified Newcastle-Ottawa scale (NOS) was employed to assess the quality of the included studies. FINDINGS: In total, 286 studies were included in this review. The majority were cross-sectional (n = 245, 85.7%) and hospital-based (n = 248, 86.7%), examining relationships between 187 different peripheral immune biomarkers and AD. Cytokines were the most frequently studied group of peripheral immune biomarkers. Evidence supported a positive association with AD for six biomarkers, including IL-6, IL-1ß, IFN-γ, ACT, IL-18, and IL-12, and a negative association for two biomarkers, including lymphocytes and IL-6R. Only a small proportion of included studies (n = 22, 7.7%) were deemed to be of high quality based on quality assessment. INTERPRETATION: Existing research on peripheral immune function and AD exhibits substantial methodological variations and limitations, with a notable lack of longitudinal, population-based studies investigating a broad range of biomarkers with prospective AD outcomes. The extent and manner in which peripheral immune function can contribute to AD pathophysiology remain open questions. Given the biomarkers that we identified to be associated with AD, we posit that targeting peripheral immune dysregulation may present a promising intervention point to reduce the burden of AD.

U.S. Breastfeeding Outcomes at the Intersection: Differences in Duration Among Racial and Ethnic Groups With Varying Educational Attainment in a Nationally Representative Sample.

BACKGROUND: As breastfeeding rates in the United States increase, barriers persist for Black, Latine, and low-socioeconomic status household dyads when compared to White and high-socioeconomic status household dyads. Previous breastfeeding disparities research has almost exclusively considered the influence of race, ethnicity, and socioeconomic status separately, although these attributes are not randomly distributed across the population. RESEARCH AIM: To identify breastfeeding duration patterns by race/ethnicity and educational attainment in a nationally representative U.S. National Immunization Survey sample. METHOD: We conducted a cross-sectional, secondary analysis of the U.S. Centers for Disease Control and Prevention's 2020 National Immunization Survey-Child public-use data. To examine breastfeeding and exclusive breastfeeding durations at the intersection of race/ethnicity and educational attainment, we created a 12-item, cross-classified variable using three educational attainment groups and four race/ethnicity groups. We used linear regressions to test these associations. RESULTS: In all, 83% of the sample breastfed. Mean durations of breastfeeding were 7.5 (SE = 1.95) months and exclusive breastfeeding duration was 4.9 (SE = 0.87) months. In adjusted models, multi-race/other high-educational attainment participants had the longest breastfeeding duration by almost 3 weeks (ß: 19.53, 95% CI [5.27, 33.79]), and Black low-educational attainment participants exclusively breastfed for 1 month less than White high-educational attainment participants (ß:-30.23, 95% CI [-40.87, -19.58]). CONCLUSIONS: Examining race/ethnicity and educational attainment together provides an intersectional understanding of breastfeeding outcomes and can inform targeted, culturally appropriate interventions.

Prenatal household size and composition are associated with infant fecal bacterial diversity in Cebu, Philippines.

OBJECTIVES: The gut microbiome (GM) connects physical and social environments to infant health. Since the infant GM affects immune system development, there is interest in understanding how infants acquire microbes from mothers and other household members. MATERIALS AND METHODS: As a part of the Cebu Longitudinal Health and Nutrition Survey (CLHNS), we paired fecal samples (proxy for the GM) collected from infants living in Metro Cebu, Philippines at 2 weeks (N = 39) and 6 months (N = 36) with maternal interviews about prenatal household composition. We hypothesized that relationships between prenatal household size and composition and infant GM bacterial diversity (as measured in fecal samples) would vary by infant age, as well as by household member age and sex. We also hypothesized that infant GM bacterial abundances would differ by prenatal household size and composition. RESULTS: Data from 16 S rRNA bacterial gene sequencing show that prenatal household size was the most precise estimator of infant GM bacterial diversity, and that the direction of the association between this variable and infant GM bacterial diversity changed between the two time points. The abundances of bacterial families in the infant GM varied by prenatal household variables. CONCLUSIONS: Results highlight the contributions of various household sources to the bacterial diversity of the infant GM, and suggest that prenatal household size is a useful measure for estimating infant GM bacterial diversity in this cohort. Future research should measure the effect of specific sources of household bacterial exposures, including social interactions with caregivers, on the infant GM.

Water, food, and the dual burden of disease in Galápagos, Ecuador.

OBJECTIVE: Rapid development in low- and middle-income countries (LMIC) has led to changes in diet that have outpaced water and sanitation improvements, contributing to a dual burden of overweight and noncommunicable disease risk factors (OWT/NCD) and undernutrition and infectious disease symptoms (UND/ID) within individuals and households. Yet, little work has examined the joint impact of water and food exposures on the development of the dual burden. METHODS: We use data from Ecuador's nationally representative Encuesta Nacional de Salud y Nutrición (ENSANUT-ECU) to test whether water access and quality and diet quality and security are associated with OWT/NCD and UND/ID among 1119 children and 1582 adults in Galápagos. Adjusted multinomial and logistic models were used to test the separate and joint associations between water and food exposures and the dual burden and its components at the individual and household levels. RESULTS: The prevalence of the dual burden of OWT/NCD and UND/ID was 16% in children, 33% in adults, and 90% in households. Diet quality was associated with a higher risk of dual burden in individuals and households. Mild food insecurity was positively associated with the risk of dual burden at the household level. No water variable separately predicted the dual burden. Joint exposure to poor water access and food insecurity was associated with greater odds of dual burden in households. CONCLUSION: Our results suggest that unhealthy diets and poor water quality contribute to the dual burden at the individual and household levels. Addressing both food and water limitations is important in LMIC.