Hyperuricemia as a Protective Factor for Mild Cognitive Impairment in Non-Obese Elderly

Inflammatory Risk Status Shapes the Association Between Uric Acid and Cognitive Function in Non-Hyperuricemia Middle Aged and Elderly

BACKGROUND

The association between uric acid (UA) and cognitive function still remains controversial. Moreover, the role of inflammation in the above association is also unclear.

OBJECTIVE

We aimed to determine the association between UA and cognitive function among non-hyperuricemia adults, and in particular, whether the association was shaped by different inflammation levels.

METHODS

From the China Health and Retirement Longitudinal Study (CHARLS), 7,272 participants aged 45 and above were enrolled in 2011. Cognitive function measurement included orientation and attention, episodic memory, and visuospatial ability. Fasting blood samples were collected to measure levels of UA and high-sensitivity C-reactive protein (hs-CRP). Generalized estimating equation models were used to evaluate the effect of UA on cognitive function in all participants and those at different levels of hs-CRP (hs-CRP <3 mg/L or ≥3 mg/L).

RESULTS

Among non-hyperuricemia adults (mean age: 58.08, 49.59% males) for a median of 7 years follow-up, participants with higher levels of UA had better cognitive function score compared to those with lower UA levels (β: 0.09, 95% confidence interval [CI]: 0.01-0.17, p = 0.023). And this association was significant under low-grade inflammation levels condition (β:0.10, 95% CI: 0.10-0.19, p = 0.024), but not in high-grade inflammation levels condition. Further, the cognitive function benefit of elevated UA existed only in people with persistent low-grade inflammation levels at a longitudinal perspective (β: 0.14, 95% CI: 0.01-0.27, p = 0.039).

CONCLUSIONS

Elevated UA levels were associated with better cognitive function in non-hyperuricemia population, especially for those at low inflammation levels.

Moderate increase of serum uric acid within a normal range is associated with improved cognitive function in a non-normotensive population: A nationally representative cohort study

Background

Associations between serum uric acid (SUA) and changes in cognitive function are understudied in non-normotensive populations, and many previous studies only considered the baseline SUA at a single time point. We aimed to examine the effects of baseline SUA and 4-year changes in SUA on cognitive changes in the non-normotensive population.

Materials and methods

In the China Health and Retirement Longitudinal Study (CHARLS), cognitive function was measured based on executive function and episodic memory in four visits (years: 2011, 2013, 2015, and 2018). We identified two study cohorts from CHARLS. The first cohort included 3,905 non-normotensive participants. Group-based single-trajectory and multi-trajectory models were applied to identify 7-year cognitive trajectories. Adjusted ordinal logistics models were performed to assess the association between baseline SUA and 7-year cognitive trajectories, and subgroup analyses were conducted according to the presence of hyperuricemia or SUA levels. The second cohort included 2,077 eligible participants. Multiple linear regression was used to explore the effect of a 4-year change in SUA on cognitive change during the subsequent 3-year follow-up.

Results

Four distinct single-trajectories of global cognitive performance and four multi-trajectories of executive function and episodic memory were identified. Higher baseline SUA levels were significantly associated with more favorable cognitive single-trajectories (OR_{Q4 vs}. _Q1: 0.755; 95% CI: 0.643, 0.900) and multi-trajectories (OR_{Q4 vs}. _Q1: 0.784; 95% CI: 0.659, 0.933). Subgroup analyses revealed that the protective effect of SUA was significant in the non-hyperuricemia groups or the low-level SUA groups. Additionally, changes in SUA could influence future cognitive changes. Compared with non-hyperuricemia participants with elevated SUA, non-hyperuricemia participants with decreased SUA and patients with persistent hyperuricemia had a higher risk for cognitive decline. Furthermore, only the Q3 group of changes in SUA could enhance global cognitive function compared with the Q1 group (β: 0.449; 95% CI: 0.073, 0.826).

Conclusion

Our study indicates that the maintenance of normal SUA levels and a moderate increase of SUA were advantageous in improving cognitive function or trajectories in a non-normotensive population. Conversely, SUA may impair cognitive function in patients with persistent hyperuricemia.

High Blood Uric Acid Is Associated With Reduced Risks of Mild Cognitive Impairment Among Older Adults in China: A 9-Year Prospective Cohort Study

Background: It remains unsolved that whether blood uric acid (UA) is a neuroprotective or neurotoxic agent. This study aimed to evaluate the longitudinal association of blood UA with mild cognitive impairment (MCI) among older adults in China.

Methods: A total of 3,103 older adults (aged 65+ years) free of MCI at baseline were included from the Healthy Aging and Biomarkers Cohort Study (HABCS). Blood UA level was determined by the uricase colorimetry assay and analyzed as both continuous and categorical (by quartile) variables. Global cognition was assessed using the Mini-Mental State Examination four times between 2008 and 2017, with a score below 24 being considered as MCI. Cox proportional hazards models were used to examine the associations.

Results: During a 9-year follow-up, 486 (15.7%) participants developed MCI. After adjustment for all covariates, higher UA had a dose-response association with a lower risk of MCI (all P_{for  trend} < 0.05). Participants in the highest UA quartile group had a reduced risk [hazard ratio (HR), 0.73; 95% (CI): 0.55–0.96] of MCI, compared with those in the lowest quartile group. The associations were still robust even when considering death as a competing risk. Subgroup analyses revealed that these associations were statistically significant in younger older adults (65–79 years) and those without hyperuricemia. Similar significant associations were observed when treating UA as a continuous variable.

Conclusions: High blood UA level is associated with reduced risks of MCI among Chinese older adults, highlighting the potential of managing UA in daily life for maintaining late-life cognition.

The relationship between serum uric acid and cognitive function in patients with chronic heart failure

BACKGROUND

Evidence has shown that serum uric acid (UA) is associated with cognitive function, but this finding remains debatable. Serum UA is commonly elevated in patients with chronic heart failure (CHF), especially in men. However, the relationship between serum UA and cognitive function in CHF populations and stratified by sex are unclear. We aimed to examine whether serum UA was independently associated with cognitive function in CHF populations after controlling for demographic, medical and psychological variables and whether there was a sex difference in the association between serum UA and cognitive function among male and female CHF patients.

METHODS

One hundred ninety-two hospitalized patients with CHF underwent an assessment of cognitive function using the Montreal Cognitive Assessment (MoCA) and the determination of serum UA. Hyperuricemia was defined as serum UA ≥7 mg/dl in men and ≥ 6 mg/dl in women. Multiple linear hierarchical regression analyses were conducted to examine the independent association between serum UA and cognitive function in CHF populations and stratified by sex.

RESULTS

The mean serum UA concentration of participants was 7.3 ± 2.6 mg/dL. The prevalence of hyperuricemia was 54.7% (105 of 192) in CHF patients, 52.9% (64 of 121) in men, and 57.7% (41 of 71) in women. In the total sample, higher serum UA was associated with poorer cognitive function independent of demographic, medical and psychological variables (β = - 0.130, ΔR² = 0.014, p = 0.015). In sex-stratified groups, elevated serum UA was independently associated with worse cognitive function in men (β = - 0.247, ΔR² = 0.049, p = 0.001) but not in women (β = - 0.005, ΔR² = 0.000, p = 0.955).

CONCLUSIONS

Higher serum UA is independently associated with poorer cognitive function in CHF populations after adjusting for confounding variables. Furthermore, elevated serum UA is independently related to worse performance on cognitive function in men but not in women. More longitudinal studies are needed to examine the association between serum UA and cognitive function in CHF populations and stratified by sex.

Uric Acid and Cognitive Function in Older Individuals

Hyperuricemia has been recognized as an independent cardiovascular risk factor in epidemiological studies. However, uric acid can also exert beneficial functions due to its antioxidant properties, which may be particularly relevant in the context of neurodegenerative diseases. In this paper, we critically revise the evidence on the relationship between serum uric acid levels and cognitive function in older individuals, focusing on the etiology of cognitive impairment (Alzheimer’s disease, Parkinson’s dementia, and vascular dementia) and on the interactive connections between uric acid, dementia, and diet. Despite high heterogeneity in the existing studies, due to different characteristics of studied populations and methods of cognitive dysfunction assessment, we conclude that serum uric acid may modulate cognitive function in a different way according to the etiology of dementia. Current studies indeed demonstrate that uric acid may exert neuroprotective actions in Alzheimer’s disease and Parkinson’s dementia, with hypouricemia representing a risk factor for a quicker disease progression and a possible marker of malnutrition. Conversely, high serum uric acid may negatively influence the disease course in vascular dementia. Further studies are needed to clarify the physio-pathological role of uric acid in different dementia types, and its clinical-prognostic significance.