The Combined Effect Of Dietary Nutrient Intake On Cognitive Function Of The Elderly

Objective:Cognitive dysfunction is one of the major health problems in the elderly.The relationship between dietary factors and cognitive function has been widely reported.However,current research results on the relationship between nutrient intake and cognitive function are inconsistent at home and abroad.At the same time,the overall effect of mixed nutrient intake on cognitive function,the nonlinear relationship between nutrient intake and cognitive function,and the interaction between nutrients were not considered.This study first identified nutrients that play a key role in different cognitive dimensions and separately analyzed the correlation between each nutrient and cognitive function in the elderly.Further explore the combined effects of mixed intake of various nutrients and the interaction be-tween nutrients on the cognitive functions of the elderly.To provide scientific basis for developing nutritional intervention measures to improve cognitive function of the elderly.Methods:Data for this study were obtained from National Health and Nutrition Ex-amination Surveys（NHANES,2011-2014）.Participants were aged 60 years and older.Cognitive function is divided into three dimensions.Cognitive function was evaluated by the Consortium to Establish a Registry for Alzheimer’s Disease（CERAD）Word Learning and delayed recall tests,the Animal Fluency Test（AFT）,and the Digit Symbol Substitution Test（DSST）.A total of 26 nutrients were included as predictive variables of cognitive func-tion,including:proteins,carbohydrates,dietary fiber,total fat,total saturated fatty acids,monounsaturated fatty acids,polyunsaturated fatty acids,cholesterol,vitamin E,vitamin A,vitamin B1,vitamin B2,niacin,vitamin B6,folic acid,vitamin B12,vitamin C,vitamin D,vitamin K,calcium,phosphorus,magnesium,iron,zinc,copper and selenium.Dietary data were obtained through two 24-hour dietary reviews and logarithmic conversion.The Least Absolute Shrinkage and Selection Operator（Lasso）was used to screen nutrients that played a key role in each of the three cognitive dimensions and the ten fold crossover method was used for internal verification.Multiple linear regression model was used to evaluate the relationship between selected key nutrients and cognitive scores,in which nutrient intake was divided into low level intake group,medium level intake group,higher level intake group and highest level intake group according to the quartile from low to high.The low level intake group was considered as the reference group.Bayesian Kernel machine Regression（BKMR）was further used to explore:1)the combined effect of mixed intake of nutrients on cognitive function;2)the nonlinear exposure-response relationship between relevant nutrients and scores of three cognitive dimensions;3)the effects of the interaction between nutrients on cognitive function.Results:1.Association between combined nutrient intake and CERAD cognitive function score in the elderly:Four key nutrients affecting CERAD cognitive score were screened by Lasso model（=0.00123）,including total fat,monounsaturated fatty acid,vitamin E and vitamin K.Multiple linear regression showed that CERAD cognitive scores were signifi-cantly increased in the vitamin E and vitamin K highest level intake group compared with low level intake group(β_{vitamin E}=2.19,95%CI:0.52-3.86;β_{vitamin k}=1.36,95%CI:0.24-2.49).BKMR analysis showed that the combined effect of the nutrients was significantly positively associated with CERAD cognitive score when all nutrient intake levels were at or above the sixtieth percentile,compared with the median for all nutrient intake levels.There was a positive correlation between total fat and monounsaturated fatty acid and CERAD cognitive score,while the exposure-response curve of vitamin E,vitamin K and CERAD cognitive score increased and then gradually flattened.There is no interaction be-tween nutrients.2.Association between combined nutrient intake and AFT cognitive function score in the elderly:Nine key nutrients affecting AFT cognitive score were screened out by Lasso model（=0.00168）,including saturated fatty acids,total polyunsaturated fatty acids,vitamin E,vitamin B2,vitamin B12,vitamin K,phosphorus,zinc and copper.Mul-tiple linear regression showed that vitamin B12 and vitamin K were significantly positively correlated with AFT cognitive function scores.Compared with the low level intake group,the increase trend of AFT cognitive function score was the highest in the medium level intake group of vitamin B12(β_{vitamin B12}=1.15,95%CI:0.30-1.99),while the AFT cognitive function score was significantly increased in the highest level intake group of vitamin K(β_{vitamin k}=1.07,95%CI:0.23-1.91).BKMR analysis showed that when all nutrient intake levels were at or above the sixtieth percentile,the combined effect of the nutrients was significantly positively correlated with AFT cognitive score when compared with the me-dian intake level of all nutrients.The single exposure response relationship showed that saturated fatty acid,polyunsaturated fatty acid,vitamin E,vitamin B2,vitamin B12,zinc and copper were positively correlated with AFT cognitive score,vitamin K and AFT cog-nitive score increased first and then slightly decreased,while phosphorus was negatively correlated with AFT cognitive score.The interaction model found an interaction between saturated fatty acids,polyunsaturated fatty acids and vitamin K.3.Association between combined nutrient intake and DSST cognitive function scores in the elderly:Six key nutrients affecting DSST cognitive score were screened by Lasso model（=0.0046）,including saturated fatty acids,total polyunsaturated fatty acids,vitamin E,vitamin B2,vitamin B12 and vitamin K.Multiple linear regression showed that polyunsaturated fatty acids,vitamin E,and vitamin B12 were significantly associated with DSST cognitive function scores.Compared with the low intake group,the increasing trend of vitamin E and DSST cognitive scores was highest in the group with higher levels of intake(β_{vitamin E}=3.15,95%CI:0.93-5.36).There was a linear correlation between polyun-saturated fatty acids and vitamin B12 and DSST cognitive score(β_{vitamin B12}=2.68,95%CI:0.52-4.83;β_{polyunsaturated fatty acids}=2.76,95%CI:0.32-5.20).BKMR analysis showed a sig-nificant positive correlation between the combined effects of the nutrients and DSST cog-nitive scores when all nutrient intake levels were at or above the sixtieth percentile,com-pared with median levels for all nutrients.The single exposure response relationship showed that saturated fatty acids,polyunsaturated fatty acids,vitamin B2 and vitamin B12were positively correlated with DSST cognitive score,and vitamin E showed an inverted U-shaped relationship with DSST cognitive score（first increased and then decreased）,while vitamin K had no correlation with DSST cognitive score.The interaction model found an interaction between saturated fatty acids,polyunsaturated fatty acids and vitamin E.Conclusions:（1）the combined effect of nutrient mixed intake was positively corre-lated with the cognitive scores of the three cognitive dimensions.（2）Saturated fatty acids,total polyunsaturated fatty acids,vitamin E,vitamin B2,vitamin B12 and vitamin K had great influence on different dimensions of cognitive function.（3）There was an interaction between vitamin K and saturated fatty acids and polyunsaturated fatty acids on AFT cogni-tive function,and there was an interaction between vitamin E and saturated fatty acids and polyunsaturated fatty acids on DSST cognitive function.Future studies need to provide additional data to confirm the observed association and further clarify the underlying bio-logical mechanisms.