Waist-to-weight index and cognitive impairment: Understanding the link through depression mediation in the NHANES.

BACKGROUND

In recent years, several studies have suggested that obesity may play an important role in cognitive impairment. Individuals with cognitive impairment often also exhibit depressive symptoms. This study aimed to explore the association between obesity and cognitive impairment and to elucidate the mediating role of depressive symptoms in this association.

METHODS

Older participants in the U.S. were examined in this cross-sectional study (n = 2391). The WWI was computed as follows: WWI = waist circumference/square root of body weight. The Consortium for Alzheimer's Disease Word Learning (CERAD-WL), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST) were used to evaluate cognitive function. Depression symptoms were evaluated with the Patient Health Questionnaire 9 (PHQ-9). Subgroup analysis and multiple logistic regression analysis were utilized to investigate the relationships between the WWI and depressive symptoms and cognitive decline. Threshold effects were computed using a two-segment linear regression model. To ascertain whether depression mediates the relationship between the WWI and cognitive impairment, mediation analysis was also employed.

RESULTS

A total of 2391 participants were included, 33.29 % of whom had cognitive impairment. There was a significant correlation between the WWI and depressive symptoms and cognitive function (P < 0.05). With increasing WWI quartiles, the prevalence of cognitive impairment increased (Q1: 27.09 %, Q2: 33.00 %, Q3: 31.44 %, Q4: 41.64 %). It was highly likely that the WWI and cognitive impairment were positively correlated (OR = 1.34, 95 % CI = 1.13, 1.59), and this link was steady across all subgroups (P for trend >0.05). A nonlinear curve with an inflection point of 10.71 connected the WWI and cognitive deterioration. A significant correlation was found between the WWI and cognitive impairment on the left side of the inflection point (OR = 3.58, 95 % CI = 1.57, 8.15). With a 5.4 % mediation rate, mediation analysis revealed that depressive symptoms mediated the relationship between cognitive impairment and the WWI.

CONCLUSIONS

There was a positive association between the WWI and the incidence of cognitive impairment in older Americans. Among other factors, depressive symptoms slightly mediated the association between the WWI and cognitive impairment. However, large-scale prospective studies are still needed to analyse the interactions between the three factors in depth.