| Objective:Heavy metals are common environmental pollutants and recent studies have shown that heavy metals have great disturbance to human endocrine.The role of heavy metal exposure in the development of obesity has attracted people’s attention.Studies in the United States,South Korea,Japan and other countries have found some relationship between cadmium and mercury exposure with obesity,but the conclusions are inconsistent.Moreover,the target population mainly focuses on adults,children and people with high exposure,and there is a lack of studies on the older adults population.In this study,older adults aged 65 and older in 9 longevity areas were investigated,to investigate the relationship between cadmium and mercury exposure with overweight/obesity and central obesity among older adults in China.Methods:The target population of this study was the 2017-2018 cohort of the Healthy Ageing and Biomarkers Cohort Study.A total of 1,889 participants were included in this study after excluding those lacking critical variables and those younger than 65 years of age.General demographic information,social and economic status,lifestyle,eating habits and exercise status were collected by means of questionnaire survey.The concentrations of cadmium and mercury in blood and urine were detected by“inductively coupled plasma mass spectrometry” as internal exposure levels.The concentrations of heavy metals in urine were analyzed after being corrected by creatinine.Multiple logistic regression model was used to analyze the relationship between cadmium and mercury exposure with overweight/obesity and the relationship between cadmium and mercury exposure with central obesity.A restricted cubic spline was used to analyze the exposure response between cadmium and mercury exposure levels with the risk of overweight/obesity and central obesity.Subgroup analysis was conducted to analyze the relationship between cadmium and mercury exposure with overweight/obesity and central obesity in different subgroups,and further exclude the interference of confounding factors.A multiplicative and additive interaction analysis was used to explore whether there were statistical and biological interactions between cadmium and mercury exposure with risk of overweight/obesity and central obesity.Results:1.Basic information of survey subjectsA total of 1889 subjects were included with an average age of 83.14±11.11years;The median concentrations of cadmium in blood,mercury in blood,cadmium in urine,and mercury in urine were 1.38 μg/L,1.44 μg/L,1.15 μg/g creatinine,0.52 μg/g creatinine,the geometric means were 1.38 μg/L,1.35 μg/L,1.19 μg/g creatinine,0.53 μg/g creatinine,respectively.The rate of overweight/obesity was35.31% and central obesity was 43.57%.2.Correlation analysis results of cadmium and mercury exposure with overweight/obesity and central obesityMultivariate logistic regression analysis showed that compared with the first quartile,the fourth quartile of blood cadmium,urine cadmium,and blood mercury had a lower risk of overweight/obesity,Odd Ratio and 95% Confidence intervals were 0.46（0.33～0.63）,0.36（0.26～0.50）,0.75（0.57～0.99）,respectively.The fourth quartile of urine cadmium blood mercury and urine mercury had a lower risk of central obesity,OR（95% CI）values were0.65（0.48～0.87）,0.64（0.49～0.84）,0.69（0.52～0.92）,respectively.3.Exposure-response analysis results of cadmium and mercury exposure levels with overweight/obesity and central obesityThe results of restricted cubic spline analysis showed that blood cadmium,urine cadmium,and blood mercury concentrations were negatively nonlinear associated with the risk of overweight/obesity,and urine cadmium concentration was negatively nonlinear associated with the risk of central obesity.That is,the higher the concentration is,the lower the risk of disease.When the concentration reaches a certain level,the risk of disease continues to decline,but the decline trend slows down.There was a negative linear correlation between blood cadmium and blood mercury concentrations with the risk of central obesity.The higher the concentrations of blood cadmium and blood mercury,the lower the risk of central obesity.4.Results of subgroup analysisSubgroup analysis showed that cadmium levels in blood and urine were more strongly associated with overweight/obesity in the uneducated population than in the educated population（P cross values were 0.03 and 0.02,respectively）.The OR（95%CI）of the corresponding fourth quartile array were 0.34（0.21～0.54）and 0.31（0.19～0.51）,respectively.Compared with females,blood mercury levels were more strongly associated with overweight/obesity,and central obesity in males（P cross values <0.01 and 0.03,respectively）,the OR（95% CI）of the corresponding quartile array were both 0.53（0.36-0.76）.Compared with older adults aged 80 and above,blood mercury levels were more strongly associated with central obesity in older adults aged 65 to 79（P cross value 0.04）,with an OR（95% CI）of 0.46（0.29～0.71）for the corresponding fourth quartile array.5.Results of interaction analysisThe results of multiplicative interaction showed that although the high blood cadmium and high blood mercury groups had a lower risk of overweight/obesity compared with the low blood cadmium and low blood mercury groups,the OR（95%CI）value was 0.43（0.27～0.71）,but the P multiplicative interaction value was 0.13,which was not statistically significant.The results show that Relative Excess Risk Due To Interaction（95% CI）was-0.247（-0.631～0.137）,The Attributable Proportion Due To Interaction（95% CI）was-0.565（-1.571～0.440）and The Synergy Index（95% CI）was 1.779（0.566～5.592）,with no statistical significance.The high urine cadmium and high urine mercury groups had a lower risk of central obesity compared with the low urine cadmium and low urine mercury groups,the OR（95%CI）value was 0.48（0.33～0.70）,but the P multiplicative interaction value was 0.48,which was not statistically significant.The results RERI（95% CI）was-0.051（-0.395～0.293）,AP（95% CI）was-0.107（-0.839～0.625）and S（95% CI）was 1.109（0.539～2.281）,with no statistical significance.Conclusion:1.The study found that older adults with higher levels of blood cadmium,urine cadmium and blood mercury had a lower risk of overweight/obesity,and older adults with higher levels of urine cadmium blood,mercury and urine mercury had a lower risk of central obesity.2.Blood cadmium,urine cadmium and blood mercury concentrations were negatively nonlinear correlated with the risk of overweight/obesity.There was a negatively nonlinear correlation between urinary cadmium concentration with the risk of central obesity,and a negatively linear correlation between blood cadmium and blood mercury concentration with the risk of central obesity.3.Compared with the educated population,the correlation between the levels of cadmium in blood and urine of the uneducated population with overweight/obesity was stronger;Compared with women,blood mercury levels were more strongly associated with overweight/obesity and central obesity in men;Compared with older adults aged 80 and above,blood mercury levels were more strongly associated with central obesity in older adults aged 65 to 79.4.The study found no interaction between cadmium with mercury exposure on overweight/obesity and central obesity. |
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