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IntroductionEpidemiological studies have shown that tooth loss may be associated with an increased risk of cognitive decline and dementia. However, some results do not show a significant association. Therefore, we performed a meta-analysis to evaluate this association.MethodsRelevant cohort studies were searched in PubMed, Embase, Web of Science (up to May 2022), and the reference lists of retrieved articles. The pooled relative risk (RR) and 95% confidence intervals were computed using a random-effects model (CI). Heterogeneity was evaluated using the I2 statistic. Publication bias was evaluated using the Begg's and Egger's tests.ResultsEighteen cohort studies met the inclusion criteria. Original studies with 356,297 participants with an average follow-up of 8.6 years (ranging from 2 to 20 years) were included in this study. The pooled RRs of tooth loss on dementia and cognitive decline were 1.15 (95% CI: 1.10–1.20; P < 0.01, I2 = 67.4%) and 1.20 (95% CI: 1.14–1.26; P = 0.04, I2 = 42.3%), respectively. The results of the subgroup analysis showed an increased association between tooth loss and Alzheimer's disease (AD) (RR = 1.12, 95% CI: 1.02–1.23) and vascular dementia (VaD) (RR = 1.25, 95% CI: 1.06–1.47). The results of the subgroup analysis also showed that pooled RRs varied by geographic location, sex, use of dentures, number of teeth or edentulous status, dental assessment, and follow-up duration. None of the Begg's and Egger's tests or funnel plots showed evidence of publication bias.DiscussionTooth loss is associated with a significantly increased risk of cognitive decline and dementia, suggesting that adequate natural teeth are important for cognitive function in older adults. The likely mechanisms mostly suggested include nutrition, inflammation, and neural feedback, especially deficiency of several nutrients like vitamin D.

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Existing research on the relationship of trade openness and economic growth is increasingly serious challenged by the reality of Chinese economic development. At the same time, compared to the United States ,Chinese trade openness has brought some adverse effects to Chinese macro economy, such as rising prices, trade imbalance, trade frictions and RMB appreciation. Openness and market size on economic growth is alternative. We make the empirical analysis on the impact of openness and market size on economic growth and concluded that for the provinces or regions of high trade openness, growth rate of trade should continue should not be higher than the rate of economic growth to maintain or reduce the degree of openness; For other provinces where the openness of the is still far away from the critical openness, they can continue to improve the way of the opening rate, and promote economic growth.

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