The Relationship Between Diet Quality And Cognitive Function In The Older Adults:The Mediating Effect Of Depressive Symptoms

Objective: With an aging population,there is growing concern about the health of older adults,who often experience memory impairment that progresses to pathological mild cognitive impairment and even dementia,which Alzheimer’s disease is the most predominant type of dementia.A growing number of research suggested that cognitive health,as well as slowing or even preventing cognitive decline and Alzheimer’s disease,can be maintained by adhering to a healthy diet,and that diet changed can benefit even when initiated later in life.Diet played an increasingly important role in cognitive function as a modifiable factor.The Healthy Eating Index-2015(HEI-2015)and its derivative dietary indicators Alternative healthy eating index-2010(AHEI-2010)were both measures of dietary quality that represented adherence to healthy degree of adherence to healthy eating guidelines.However,the association between the HEI-2015 and AHEI-2010 with cognitive function had been little studied and the mechanisms were unclear.In addition,healthy diet was significantly associated with milder depressive symptoms,which in turn was an important risk factor for cognitive decline,so depressive symptoms may play a mediating role in diet quality and cognitive function.In summary,this study aimed to investigate the association between diet quality and cognitive function in older adults and the mediating role of depressive symptoms in it.Methods: This study used the data of NHANES2011-2012 and 2013-2014,and conducted a study on the association between diet and cognitive function with elderly people aged 60 and over.Cognitive function tests include Alzheimer’s Disease Registry Word Learning Test(CERAD),Digit Symbol Substitution Test(DSST)and Animal fluency test(AFT).In order to reflect the information of the global cognitive function,after the normalization of the above three cognitive scores,and then take the average to obtain the Z-score reflecting the global cognitive function.NHANES individual food data and dietary data from the Food Pattern Equivalent Database(FPED)were used to estimate food supply to establish the HEI-2015 and AHEI-2010 food groups.Each food is classified according to the USDA food code.After HEI-2015 and AHEI-2010 food groups and nutrients were created,SAS codes were constructed to calculate HEI-2015 and AHEI-2010 scores.The mediator variable depressive symptoms was measured by a health questionnaire,which consisted of 9 items,each item ranged from 0 to 3 points,and the total score ranged from 0 to 27 points.With HEI-2015 and AHEI-2010 as independent variables,cognitive function and depressive symptoms as dependent variables,multiple linear regression model and weighted quantile and regression model were fitted to analyze the relationship between HEI-2015 and cognitive function and depressive symptoms and the relationship between AHEI-2010 and cognitive function and depressive symptoms,and to explore the contribution of each component of the two dietary indicators to cognitive function and depressive symptoms.The stepwise method was used to test whether there was a mediating effect of depressive symptoms between diet quality and cognitive function,and the Sobel method was further used to test the mediating effect and calculate the proportion of the mediating effect.Results:1.Basic characteristics of the population.A total of 2644 participants were enrolled in this study,with an average age of69.43 ± 6.77 years old.The average scores of HEI-2015 and AHEI-2010 were57.67±13.24 and 47.06±9.88 respectively.Among them,gender,race,marital status,education level,smoking,stroke indicators have significant differences in different HEI-2015 and AHEI-2010 quantile levels.Cognitive scores increased with the increase of HEI-2015 and AHEI-2010 scores.2.The association between dietary quality and cognitive function.In the HEI-2015 index,compared with the lowest quartile,the highest quartile of HEI-2015 was positively associated with CERAD(β: 1.10;95%CI: 0.26,1.94;P=0.012),DSST(β: 3.16;95%CI: 1.19,5.13;P=0.003),AFT(β:1.99;95%CI: 1.14,2.85;P<0.001)and Z-score(β: 0.21;95%CI: 0.12,0.30;P<0.001).There was a significant linear trend.In the CERAD cognitive test,the weight distribution showed that seafood and plant protein,total vegetables,sodium and whole fruit account for more than 10%(weight is 38%,18.7%,11.6%,11%,respectively).In the DSST cognitive test,the weight distribution showed that the weight of whole fruit,seafood and plant proteins,total protein and sodium accounted for more than 10%(18%,17.4%,17.1% and 10.9%,respectively).In the AFT cognitive test,the weight distribution showed that seafood and plant proteins,whole fruits,sodium,total vegetables and total protein accounted for more than 10% of the weight(24.8%,16.5%,14.1% and 11.8%,respectively).In the Z-score cognitive test,the weight distribution showed that seafood and plant proteins,whole fruits,total vegetables and sodium accounted for more than 10% of the weight(33.5%,16%,15.5% and 11.7%,respectively).In the AHEI-2010 index,multiple linear regression analysis showed that the highest quartile of AHEI-2010 was significantly positively associated with DSST(β:3.37;95%CI: 2.03,4.71;P<0.001),AFT(β: 1.14;95%CI: 0.25,2.04;P<0.01)and Z-score(β: 0.14;95%CI: 0.06,0.23;P<0.01),and there was a significant linear trend.The component weights of WQS index showed that drinking,nuts,beans,processed red meat and vegetables accounted for more than 10% of the weights in the CERAD cognitive test(36.6%,24.6%,13.2%,10.10%,respectively).In the DSST cognitive test,nuts,beans and red meat accounted for more than 10% of the weights(47.6%,18.9%,10.5%,respectively).In the AFT cognitive test,nuts,legumes,drinking and processed red meat accounted for more than 10% of the weights(23.3%,22.8%,14.1% respectively).In the comprehensive Z-score cognitive test,nuts,legumes,drinking and red meat accounted for more than 10%of the weights(53.7%,15.5%,12.5%,respectively).3.Relationship between dietary quality and depressive symptoms.The highest quartile of HEI-2015 was significantly negatively associated with depressive symptoms(β:-0.76;95%CI:-1.19,-0.32;P<0.001),and there was a significant linear trend from the lowest quartile to the highest quartile.In depressive symptoms,the weight distribution showed that the weight of whole fruit,green leafy vegetables and legumes,total vegetables and added sugar accounted for more than 10%(the weights were 22.8%,22.7%,11.8% and 10.3%,respectively).The highest quartile of AHEI-2010 was negatively associated with depressive symptoms(β:-1.27% CI:-1.80,0.75;P<0.001),and the linear trend was significant,that is,with the increase of the quartile of AHEI-2010,the depressive symptoms were significantly lighter.The analysis of the weight of depressive symptoms showed that drinking alcohol and nuts and beans have a large weight(the weight is50.50% and 12% respectively),and the weights of other components were all less than 10%.4.The relationship between depressive symptoms and cognitive function.Depressive symptoms were negatively associated with CERAD(β:-0.11;95%CI:-0.20,-0.03),DSST(β:-0.53;95%CI:-0.73,-0.33;P<0.001),AFT(β:-0.11;95%CI:-0.18,-0.05;P < 0.001)and Z-score(β:-0.02;95%CI:-0.03,-0.01;P<0.001).That is,people with more serious level of depressive symptoms tended to have lower score of cognitive function.5.Mediation analysis:The results showed that depressive symptoms played a significant mediating role between dietary quality and cognitive function.The mediating effects in HEI-2015 and CERAD,DSST,AFT and comprehensive Z scores were 14.14%,9.10%,9.15% and 10.47%,respectively.The mediating effects in AHEI-2010 and CERAD,DSST,AFT and comprehensive Z scores were 11.74%,9.78%,5.84% and9.06%,respectively.Conclusion: This study showed that following the HEI-2015 or AHEI-2010 diet were significantly associated with better cognitive function,especially alcohol consumption,nuts and legumes,processed meat,vegetables,fruits and plant protein nutrients contributed significantly to reducing the risk of cognitive impairment in specific dimensions.In addition,depressive symptoms may partially mediate the relationship between diet quality and cognitive function.