ABSTRACT
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.
ABSTRACT
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.