The Associations Of A Capsaicin-rich Diet With Blood Amyloid-? Levels And Cognitive Function

Background and objectiveAlzheimer's disease(AD),the most common form of dementia,is he central nervous system degenerative disease which characterized by the progressive loss of cognition,memory and behaviour in elderly adults and involved the interactions of genes,proteins,cells,neurotransmitters and the environment.Previous studies suggest that dietary patterns may have certain influences on cognitive function;also diet may play an important role in the prevention of AD.For example,the consumption of foods that are high in sodium reduces cognitive function,whereas another study found that there are significant associations between the inadequate intake of animal oil and the prevalence of mild cognitive impairment.Capsaicin-rich diets are common worldwide.Capsaicin has been shown to have favourable effects on various diseases which including atherosclerosis,cardiovascular diseases,stroke,obesity,hypertension,cancer,gastrointestinal and inflammatory diseases and has been shown to reduce the total and cause specific mortality.The impact of capsaicin on Alzheimer's disease(AD),which is the most common form of dementia in the elderly,remains unknown.So in the present study,we aimed to investigate the associations between capsaicin dietary intake and cognitive function and blood markers of AD in a cohort of middle-aged and elderly community subjects.MethodsThis is a cross-sectional study,which investigated population above 40 years old from Daping and Xinggang Qi community of Yuzhong District in the city of Chongqing from March to June in 2014.Survey respondents need voluntarily participate.We adopted questionnaire survey to collect data regarding cognitive function and capsaicin dietary patterns.The self-reported Food Frequency Questionnaire(FFQ)was originally designed to identify the eating habits of Chongqing.Total scores could range from 4 to 16 for the FFQ for a capsaicin-rich diet,which represented the degree of the capsaicin richness in each subject's diet.The FFQ included four questions(four aspects)as follows: 1)the degree of chili enjoyment2)the degree of spiciness enjoyed 3)the frequency of chili consumption 4)the quantity of chili eaten.And also the Chinese version of the Mini Mental State Examination was used to assess cognitive function.Additionally,the following demographic information was collected: age,gender,education level,weight,height,smoking history,and alcohol consumption.Medical history-taking included identifying diagnoses of hypertension,hypercholesterolaemia,diabetes,or atrial fibrillation.For each participant,a fasting blood sample was collected.Serum A?40 and A?42 levels were measured by human A?40 and A?42 ELISA kits.Statistical analyses were conducted using SPSS 17.0 software.For each question,gender,education level,smoking history,alcohol consumption,body mass index(BMI),hypertension,hypercholesterolemia,diabetes and atrial fibrillation were considered to be categorical variables which analyzed by chi-square test.All clinical continuous variables such as age,MMSE score,serum A?40 or A?42 levelswere presented as the mean ± standard error(M ± s.e.)and were compared by one-way ANOVA.The total scores of the FFQ for capsaicin were placed in tertiles,namely lower(4-7),middle(8-11)and higher(12-16)tertiles,which represented the degree of the capsaicin richness in each subject's diet.To explore the association between a capsaicin-rich diet and cognitive function or A? levels,we established three models including one univariate analysis model,two multivariate analysis model which can adjust different sets of confounding factors.Spearman correlation analysis and partial correlation analysis were used to evaluate the correlation between a capsaicin-rich diet and the blood markers of AD and cognitive function,following adjustments for individual characteristics.ResultsThe results of the questionnaire and health examination were included in the standard form.A total of 710 subjects were investigated,after exclusions,338 subjects qualified for our study.Differences were observed in age,gender,alcohol consumption,smoking history,MMSE scores and serum A?40 levels across all four categories of questions.In univariate analysis,MMSE scores(r=0.209,p<0.001),serum A?40 levels(r=-0.149,p=0.006),but not serum A?42 levels(r=0.17,p=0.757)and total serum A? levels(r=-0.097,p=0.075),were significantly correlated with total capsaicin diet scores.In model one,total capsaicin diet scores were associated with MMSE scores(r=0.165,p=0.002),serum A?40 levels(r=-0.200,p<0.001),and total serum A? levels(r=-0.144,p=0.008),but not serum A?42 levels(r=-0.024,p=0.66)and the ratio of A?42/A?40(r=0.072,p=0.187).In model two,total capsaicin diet scores were also associated with MMSE scores(r=0.182,p=0.001),serum A?40 levels(r=-0.193,p<0.001)and total serum A? levels(r=-0.14,p=0.011),but not serum A?42 levels(r=-0.22,p=0.692)and the ratio of A?42/A?40(r=0.072,p=0.194).Multivariate analysis suggested total capsaicin diet scores were positively associated with MMSE scores,and inversely correlated with serum A?40 levels,and total serum A? levels,but not serum A?42 levels.ConclusionThis study suggests that a capsaicin-rich diet may exert favourable effects on cognitive function and AD blood biomarkers and in middle-aged and elderly adults.