The Mediating Effects Of Dietary And Serum Inflammatory Markers On Pulmonary Function

Objective:Based on the multi-stage large sample database of the National Health and Nutrition Examination Survey（NHANES）,this study analyzed the dietary and nutrient intake patterns of adults,took dietary and serum inflammatory markers as mediating variables and established the mediating effect models of dietary inflammatory factor mediating dietary pattern and pulmonary function indexes,and inflammatory markers in serum mediating abdominal obesity and pulmonary function indexes,respectively.We further evaluated the relationship between different level combinations of three serum inflammatory markers and pulmonary function indexes.Methods:This study included two parts.Part I:Based on the baseline data collected by the NHANES from 2007 to 2012,we explored the mediating effect of the dietary inflammatory index（DII）on dietary patterns and pulmonary function.Pulmonary function indexes included forced expiratory volume in 1s（FEV1）,forced vital capacity（FVC）,percentage of predicted forced expiratory volume in 1second（FEV1%）and percentage of predicted forced vital capacity（FVC%）.Firstly,k-means cluster analysis was used to study the dietary patterns of American adults,and further analyze the intake of various food types and nutrients in different dietary patterns.Then the individual DII was calculated according to the intake of various dietary components.We used Baron and Kenny’s causal step method and fitted multiple linear regression model to judge the mediating effect of DII（mediator variable）on dietary patterns（independent variable）and pulmonary function（dependent variable）.Subsequently,the Karlson/Holm/Breen（KHB）model was used to test the mediating effect and calculate the percentage of mediating effect in the total effect.Part II:Based on the baseline data collected in NHANES from 2007 to 2010,we explored the mediating effect of inflammatory markers in serum on abdominal obesity and pulmonary function.Serum inflammatory markers included C-reactive protein（CRP）,white blood cells（WBC）,and neutrophil to lymphocyte ratio（NLR）.We analyzed the mediating effect of serum inflammatory markers（mediator variable）on abdominal obesity（independent variable）and pulmonary function（dependent variable）.And the combined effects of three serum inflammatory markers on pulmonary function were further analyzed.The above analyses adjusted for a series of covariates,such as age,gender,race,education,marital status,economic status,body mass index（BMI）,smoking,hypertension,diabetes,history of respiratory diseases,and energy intake.Results:A total of 11,260 subjects aged 20-79 were included in the first part of this study.（1）The results of cluster analysis showed that there were four dietary intake patterns in American adults,including high milk and fruit mode（relatively high intake of vitamins A,C,and D）,high snack and dessert mode（relatively high intake of sugars,carbohydrates,and total fat）,balanced diet mode（relatively high intake of protein,fat,dietary fiber,major elements,trace elements,vitamin B,and vitamin E）,and low nutrient mode（relatively low intake of all dietary components）.（2）CRP was negatively correlated with FEV1,FVC,FEV1%and FVC%,respectively(β_{lg CRP}=-143.28,-176.67,-4.08,-4.05,P<0.001);WBC was negatively correlated with FEV1,FVC,FEV1%and FVC%,respectively(β_{lg WBC}=-406.25,-471.76,-8.11,-6.63,P<0.001);NLR was negatively correlated with FEV1,FVC and FEV1%,respectively(β_{lg NLR}=-138.83,-90.94,-2.48,P<0.01),the difference was statistically significant.（3）DII was negatively correlated with FEV1,FVC,FEV1%and FVC%（β=-15.77,-23.44,-0.25,-0.30,P<0.01）,the difference was statistically significant.（4）The mediating effect of DII on balanced diet pattern and FEV1 was 10.41（95%CI:0.83～19.99,P<0.05）,accounting for 11.44%of the total effect;The mediating effect on FVC was 14.69（95%CI:1.71～21.67,P<0.05）,accounting for 11.46%of the total effect;The mediating effect on FVC%was 0.17（95%CI:0.01～0.37,P<0.05）,accounting for 24.10%of the total effect.The mediating effect of DII on the association between balanced diet pattern and FEV1%was not statistically significant.（5）The mediating effect of DII on low nutrient pattern and FEV1 was-12.41（95%CI:-22.37～-2.58,P<0.001）,accounting for 16.78%of the total effect;The mediating effect on FVC was-17.52（95%CI:-30.50～-4.55,P<0.05）,accounting for 17.06%of the total effect.The mediating effect of DII on the association between low nutrient pattern and FEV1%and FVC%was not statistically significant.A total of 7,209 subjects aged 20-79 were included in the second part of this study.（1）The mediating effect of CRP on abdominal obesity and FEV1 was-15.98（95%CI:-31.06～-0.89,P<0.05）,accounting for 23.14%of the total effect;The mediating effect on FVC was-20.79（95%CI:-40.29～-1.29,P<0.01）,accounting for 18.58%of the total effect;The mediating effect on FEV1%was-0.47（95%CI:-0.91～-0.03,P<0.05）,accounting for 12.67%of the total effect;The mediating effect on FVC%was-0.50（95%CI:-0.96～-0.04,P<0.05）,accounting for 10.30%of the total effect.（2）The mediating effect of WBC on abdominal obesity and FEV1 was-13.86（95%CI:-26.82～-0.90,P<0.05）,accounting for 20.17%of the total effect;The mediating effect on FVC was-19.18（95%CI:-36.84～-1.53,P<0.01）,accounting for 17.14%of the total effect;The mediating effect on FEV1%was-0.23（95%CI:-0.47～-0.01,P<0.05）,accounting for 3.35%of the total effect;The mediating effect on FVC%was-0.26（95%CI:-0.52～-0.02,P<0.05）,accounting for 5.46%of the total effect.（3）The mediating effects of NLR on abdominal obesity and FEV1,FVC,FEV1%,and FVC%were not statistically significant.（4）By analyzing various combinations of different levels of three inflammatory biomarkers（CRP,WBC,and NLR）,it was found that the combination of high CRP,high WBC,and/or high NLR had the greatest impact on the indexes of lung function.Conclusions:（1）There are mainly four dietary intake patterns for American adults,namely,high milk and fruit pattern,high snack and dessert pattern,balanced diet pattern,and low nutrient pattern;（2）The levels of inflammatory factors in diet and serum were negatively correlated with lung function;（3）Dietary inflammatory factors mediated the relationship between dietary pattern and pulmonary function indexes;Serum inflammatory markers mediated the relationship between abdominal obesity and pulmonary function.It is suggested to have a balanced diet,actively participate in physical exercise and avoid obesity,so as to reduce the level of inflammatory markers in the body and improve lung function.