Greenness, cognitive impairment and dementia: a systematic review and meta-analysis

BACKGROUND AND AIM: Many recent studies identified the benefits of green space exposure for the improvment of human health, especially mental health. The involved patways could be increased physical activity, improved sleep quality, reduced stress and also increased social interaction. The relation between greenness and cognitive decline, however, is still uncertain. METHODS: We searched epidemiological studies related to green space exposure and cognitive impairment and dementia in two electronic databases (PubMed and EMBASE) using terms related to residential greenness, including Normalized Difference Vegetation Index-NDVI, land cover, land use, green index, greenness, green space, urban park, urban green and recreational park, along with cognitive impairment, decline and dementia. A meta-analysis comparing the highest versus the lowest greenness exposure and risk of cognitive decline was performed using a random-effects model. RESULTS:Out of 64 studies retrieved from the online search 11 studies were eligible for the review. The majority of included reports used satellied-derived NDVI, while the remaining studies used land cover maps to determine the greenness-related exposure areas. Cognitive impairment or dementia risk are calculated using different exposure types (greenness within a buffer, the areal radius, or greenness of census block) at subject residential address. Overall, summary risk ratio-RR showed no effect of greenness on cognitive decline (RR 0.99, 95% confidence interval-CI 0.91-1.07), whereas a slight indication of a beneficial effect of NDVI emerged (RR 0.96, 95%CI 0.90-1.03). Two studies that reported correlation coefficents only did not suggest an association between cognitive impairment and dementia measurement. CONCLUSIONS:Overall, our study yielded limited evidence of a protective effect of greenness on cognitive decline. The rapid evolution of greenness definition over time and the limitations in exposure assessment, however, suggest the need to further investigate this issue in order to draw more reliable conclusions. KEYWORDS: Green space, Neurodegenerative outcomes, Environmental epidemiolog

Atrial Fibrillation and the Risk of Early‐Onset Dementia: A Systematic Review and Meta‐Analysis

BACKGROUNDRecent studies have identified an increased risk of dementia in patients with atrial fibrillation (AF). However, both AF and dementia usually manifest late in life. Few studies have investigated this association in adults with early‐onset dementia. The aim of this study was to investigate the relationship between AF and early‐onset dementia. METHODS AND RESULTSWe searched the PubMed/MEDLINE, Embase, and Scopus databases through April 15, 2022, for studies reporting on the association between AF and dementia in adults aged <70 years, without language restrictions. Two reviewers independently performed the study selection, assessed the risk of bias, and extracted the study data. We performed a meta‐analysis of early‐onset dementia risk according to occurrence of AF using a random‐effects model. We retrieved and screened 1006 potentially eligible studies. We examined the full text of 33 studies and selected the 6 studies that met our inclusion criteria. The pooled analysis of their results showed an increased risk of developing dementia in individuals with AF, with a summary relative risk of 1.50 (95% CI, 1.00–2.26) in patients aged <70 years, and 1.06 (95% CI, 0.55–2.06) in those aged <65 years. CONCLUSIONSIn this systematic review and meta‐analysis, AF was a risk factor for dementia in adults aged <70 years, with an indication of a slight and statistically imprecise excess risk already at ages <65 years. Further research is needed to assess which characteristics of the arrhythmia and which mechanisms play a role in this relationship

A Systematic Review and Dose-response Meta-analysis on Fluoride Exposure and Neurodevelopmental Toxicity in Children

Background The possible harmful effect of fluoride exposure on neurodevelopment in children is widely discussed, however, the magnitude of this relation is still controversial. The aim of this systematic review and meta-analysis was to characterize this relation through a dose-response approach. Methods/Approach We performed an online literature search in PubMed, Web of Science and Embase up to September 10, 2022. From each eligible study we extracted the effect size as a mean difference (MD) of intelligence quotient (IQ) scores and its 95% confidence intervals (CI). We performed a meta-analysis comparing the highest versus lowest fluoride exposure using a random-effects model, stratifying for type of exposure (fluoride in drinking water or urinary fluoride). Finally, we quantitively assessed such relation by performing a one-stage dose-response meta-analysis based on a cubic spline random-effects model. Results Out of 1955 potentially relevant records retrieved through a systematic literature search, we identified 34 eligible studies for review; 32 were also included for meta-analysis. The analysis comparing the highest-versus-lowest exposure showed decreased IQ scores for both water and urinary fluoride with MD of -6.62 (95% CI -8.61, -4.63) and -3.58 (95% CI -7.28, 0.12), respectively. The dose-response analysis showed a decrease in IQ score from 1 mg/L, considerably steeper above 2.5 mg/L for water fluoride. The dose-response curve for urinary fluoride showed a weaker but constant decrease in IQ scores with increasing fluoride levels. Conclusions Overall, a substantial consistency in the effect direction emerged, with adverse effects of different magnitude on children’s intelligence, arising from rather low fluoride exposure previously considered safe from a public health perspective. However, potential methodological limitations, such as heterogeneity in outcome measures and lack of consideration of possible confounders in some of the studies, may have affected these findings

Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis

Introduction: Fluoride exposure may have various adverse health effects, including affecting thyroid function and disease risk, but the pattern of such relation is still uncertain. Methods: We systematically searched human studies assessing the relation between fluoride exposure and thyroid function and disease. We compared the highest versus the lowest fluoride category across these studies, and we performed a one-stage dose-response meta-analysis for aggregated data to explore the shape of the association. Results: Most retrieved studies (27 of which with a cross-sectional design) were conducted in Asia and in children, assessing fluoride exposure through its concentrations in drinking water, urine, serum, or dietary intake. Twenty-four studies reported data on thyroid function by measuring thyroid-related hormones in blood (mainly thyroid-stimulating-hormone - TSH), 9 reported data on thyroid disease, and 4 on thyroid volume. By comparing the highest versus the lowest fluoride categories, overall mean TSH difference was 1.05 μIU/mL. Dose-response curve showed no change in TSH concentrations in the lowest water fluoride exposure range, while the hormone levels started to linearly increase around 2.5 mg/L, also dependending on the risk of bias of the included studies. The association between biomarkers of fluoride exposure and TSH was also positive, with little evidence of a threshold. Evidence for an association between fluoride exposure and blood concentrations of thyroid hormones was less evident, though there was an indication of inverse association with triiodothyronine. For thyroid disease, the few available studies suggested a positive association with goiter and with hypothyroidism in both children and adults. Conclusions: Overall, exposure to high-fluoride drinking water appears to non-linearly affect thyroid function and increase TSH release in children, starting above a threshold of exposure, and to increase the risk of some thyroid diseases