A U-shaped Association of Breastfeeding Duration with Cognitive Impairment in Chinese Postmenopausal Women

Association of reproductive factors with dementia: A systematic review and dose-response meta-analyses of observational studies

BACKGROUND

Associations between endogenous estrogen exposure indicators and risk of subtypes of dementia have been unclear.

METHODS

Databases (PubMed, EMBASE and Web of Science) were searched electronically on 1st July and updated regularly until 12nd November 2021. Observational studies of English language were selected if reported an effect estimate [e.g., odds ratio (OR), rate ratio (RR) or hazard ratio (HR)] and 95% CI for the association between any exposure (age of menarche, age at menopause, reproductive period, estradiol level) and any endpoint variable [all-cause dementia, Alzheimer's disease (AD), vascular dementia (VD), cognitive impairment (CI)]. Random-effects models and dose-response meta-analyses were used to calculate estimates and to show the linear/nonlinear relationship. PROSPERO CRD42021274827.

FINDINGS

We included 22 studies (475 9764 women) in this analysis. We found no clear relationship between late menarche (≥14 vs <14 years) and dementia, CI in categorical meta-analysis compared to a J-shape relationship in dose-response meta-analyses. Later menopause (≥45 vs <45 years) was consistently associated with a lower risk of all-cause dementia (pooled RR: 0.87, 95%CI: 0.78-0.97, I²=56.0%), AD (0.67, 0.44-0.99, I²=78.3%), VD (0.87, 0.80-0.94) and CI (0.82, 0.71-0.94, I²=19.3%) in categorical meta-analysis, showing similar results in dose-response meta-analyses. An inverse relationship between longer reproductive duration (≥35 vs <35 years) and dementia was observed in dose-response meta-analysis. In addition, estradiol levels after menopause were inversely correlated with the risk of AD and CI.

INTERPRETATION

In this study, later menopause and longer reproductive period were associated with a lower risk of dementia, while the relationship for menarchal age was J-shaped. There was an inverse relationship between higher postmenopausal estrogen levels and risk of AD and CI. Longitudinal study are needed to further explore the association between life-time estrogen exposure and risk of subtypes of dementia.

FUNDING

Start-up Foundation for Scientific Research in Shandong University.

Association between serum uric acid level and mortality in China

BACKGROUND

Whether there is an association between serum uric acid (SUA) level and risk of mortality in the general population remains unclear. Based on the China National Survey of Chronic Kidney Disease linked to mortality data, a population-based cohort study was performed to investigate the association between SUA level and all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality in China.

METHODS

The survival status of participants in the cross-sectional survey was identified from January 1, 2006 to December 31, 2017. Only 33,268 individuals with complete SUA data among the 47,204 participants were included in the analysis. We determined the rates of all-cause mortality, CVD mortality, and cancer mortality. We used Cox proportional hazards regression models to evaluate the effect of the SUA level on mortality.

RESULTS

During a total of 297,538.4 person-years of follow-up, 1282 deaths occurred. In the Cox proportional hazards regression model, the rate of all-cause mortality, CVD mortality, and cancer mortality had a U-shaped association with SUA levels only in men, whereas no significant associations were detected in women. For all-cause mortality in men, the multivariable-adjusted hazard ratios (HRs) in the first, second, and fourth quartiles compared with the third quartile were 1.31 (95% confidence interval [CI] 1.04-1.67), 1.17 (95% CI 0.92-1.47), and 1.55 (95% CI 1.24-1.93), respectively. For CVD mortality, the corresponding HRs were 1.47 (95% CI 1.00-2.18), 1.17 (95% CI 0.79-1.75), and 1.67 (95% CI 1.16-2.43), respectively. For the cancer mortality rate, only a marginally significant association was detected in the fourth quartile compared with the third quartile with an HR of 1.43 (95% CI 0.99-2.08).

CONCLUSIONS

The association between SUA and mortality differed by sex. We demonstrated a U-shaped association with SUA levels for all-cause and CVD mortalities among men in China.