The Association Between The Dietary Salt Intake And Depressive Symptoms In A General Adult Population

ObjectiveThis large-scale cross-sectional study aims to investigate how dietary salt intake is associated with depressive symptoms in Chinese healthy adults.So as to provide a basis for prevention strategies and nutritional dietary treatment for high-risk populations with depression.MethodsThe baseline data of this cross-sectional study was derived from the Tianjin Chronic Low-Grade Systemic Inflammation and Health Cohort Study(TCLSIHealth),a prospecting dynamic cohort study was designed to explore the association between chronic low-grade inflammation and health in the Tianjin population.From 2013 to2016,the subjects who had received at least one health examination was conducted at the Health Management Center of Tianjin Medical University General Hospital,and had completed the food frequency questionnaire and depression scale during the examination were enrolled.A total of 27,875 research objects,but only 23,510 people who met the exclusion and inclusion criteria and were willing to sign an informed consent form to join the cross-sectional study.For follow-up statistical analysis,we collected other variables of each subjects from questionnaires(including social demographic data,family history,the condition of drug use,personal disease history,drinking status and smoking status,physical activity,dietary status,and lifestyle habits).Physical examination(including height,weight,blood pressure,waist circumference,etc.)and laboratory tests(including triglycerides,low-density lipoprotein cholesterol,high-density lipoprotein cholesterol,fasting blood glucose,total cholesterol,etc.)The dietary salt intake was assessed using a combination of the valid food frequency questionnaire(FFQ)and the standardized salt coefficient assignments for each food,the salt intake are divided into four levels of the male population : level1 :4.75 g/d,level 2: 6.67 g/d,level 3 :8.53 g/d,level 4: 12.33 g/d;The four levels of the female population : level 1: 3.73 g/d,level 2: 5.24 g/d,level 3: 6.75 g/d,and level4 : 9.70 g/d.The depressive symptoms was assessed using the Chinese version of the Zung Self-reported Depression Scale(SDS),which had tested for reliability and validity.This study delineated a total score of 45 points as a rating for depression,and added two points of 48 points and 50 points in order to increase the sensitivity of depression assessment.In addition,if the subject is taking a depressive drug or reports a history of depression,it is considered depression.To compared the basic characteristics of the population between the depression group and the healthy group,the logistic regression analysis was used to analyze the qualitative variables,and the quantitative variables were analyzed by analysis of variance.Using depressive symptoms as a dependent variable,the quartile level of dietary salt intake was used as an independent variable,and the adjusted logistic regression models were used to evaluate the association between dietary salt intake and depressive symptoms.ResultsAccording to the self-rating depressive symptoms scale with cut-off point of 45,48 or 50 : the prevalence of depressive symptoms with 45 cut-off point was 16.4% for the whole population,and 15.3% for the males,17.6% for females;The prevalence of depressive symptoms with 48 cut-off point was 9.54% for the whole population,and9.0% for the males,10.14% for females;The prevalence of depressive symptoms with50 cut-off point was 6.24% for the whole population,and 5.96% for the males,6.55%for females.In all outcomes,the depressive symptoms prevalence of female was higher than in men(P < 0.0001).In the comparison of the basic characteristics of the whole population,the differences of physical activity,education level,family monthly income,occupational category,total dietary energy intake,smoking and drinking status,etc.were statistical significant between populations with depressive symptoms and non-depressed groups(P <0.05).In the comparison of the basic characteristics of the different dietary intake levels of the whole population,the differences of the age,physical activity,total energy intake,smoking and drinking status,education level,occupational category,multiple metabolic diseases,etc.were statistically significant(P for trend < 0.05).The similar results were observed in further subsequent gender stratification analysis.Using multivariate logistic regression analysis,after adjusting for a number of potential confounding factors through four models,the odds ratio(95% confidence interval)of depressive symptoms in the different levels of dietary salt intake in the whole population was 45,48,and 50,respectively: 1.26(1.10,1.43),1.03(0.92,1.15),1.00,1.23(1.10,1.37)(P <0.05);1.24(1.06,1.46),1.04(0.91,1.20),1.00,1.19(1.04,1.37)(P < 0.05);1.22(1.01,1.48),0.92(0.77,1.09),1.00,1.24(1.05,1.47)(P <0.05).There is a U-shaped association between dietary salt intake and depressive symptoms in the population,the results were statistically significant.Similar results were observed between male and female populations.ConclusionsThis large population-based study shows a U-shaped association between dietary salt intake and depressive symptoms in Chinese healthy adults.It is mean that during the general population and male-female populations,compared with moderate dietary salt intake,the high and low levels of salt intake may increase the risk of depressive symptoms.Our study is a cross-sectional study,so that the causal relationship of variables cannot be determined.Further cohort studies and clinical randomized controlled trials are needed to assess the exact mechanism between dietary salt and depressive symptoms.