A Systematic Review And Empirical Study Of The Relationship Between Body Mass Index And Mortality And Quality Of Life From The Perspective Of Obesity Paradox

Objective:Overweight and obesity are popular in developed and developing countries.It is an important public health problem in the world.Many studies have shown that overweight and obesity increase the risk of diabetes,cardiovascular disease,cancer and other diseases,increase the risk of death,reduce the quality of life,and bring a heavy burden to individuals and society.However,in recent years,studies have found that,relative to normal weight,the mortality of overweight and obesity is lower,the survival prognosis is better,and the quality of life is higher.This phenomenon was called obesity paradox.The amount of studies on obesity paradox has increased rapidly,and this phenominon was reported in more and more patients.The purpose of this study is to systematically analysize researches on obesity paradox and understand the research status,and to explore the relationship between body mass index(BMI)and mortality and life quality in the general Asian populations.So that we can better understand the obesity paradox and to explore the differences between different BMI classifications.Methods:(1)Bibliometrics method was used to analyze the studies on obesity paradox in different contents.(2)Systematic review and meta-analysis were conducted to explore the relationships of different BMI classification and mortality and quality of life.(3)Data of several cross-sectional surveys was usd to analyze the association between BMI and quality of life in Chinese population.Obesity was categorized according to the International,Asian and Chinese BMI classifications.Least square analysis and logistic regression were performed.Results:(1)The results of bibliometric analysis showed:a total of 707 researches published from 2002 to 2018 were included.The researches on obesity paradox showed a stable trend of increase;Lavie,CJ was the most productive author and there was no core authors;the first three amount of seareches were published on Am J Cardiol、Int J Cardiol和 J Am Coll Cardiolmost,and most of studies conducted in United States.The design of most subjects recruited in the studies on obesity paradox were prospective chort studies,most of the participants were cardiovascular disease patients and the old.The sample range varied from 30 to 900 thousands;most of the studies used the WHO classifications of BMI and most of the studies used mortality as the main outcome.(2)The systematic review of BMI and mortality showed that there were 43 studies met the inclusion criteria and 33 studies were included in meta-analysis.The 43 researches were published from 2001 to 2008.The sample were totaled to 3218065 with 187877 deaths.For WHO classification,the combined RR(95%CI)for underweight,overweight and obesity were 1.36(1.26,1.46),0.91(0.86,0.95)and 0.93(0.87,0.98)seperately.The relationship between overweight and mortality was inconsistent in subgroups of sample size and time of follow-up.For Asian classification,the combined RR(95%CI)for underweight,overweight and obesity were 1.15(1.46,1.65),0.88(0.82,0.94)and 1.03(0.92,1.13)seperately.The relationship between BMI and mortality was inconsistent in subgroups of sample size.For Chinese classification,the combined RR(95%CI)for underweight,overweight and obesity were(1.21,1.43),0.91(0.87,0.96),and 1.01(0.97,1.05)seperately.The relationship between BMI and mortality was inconsistent in subgroups of sample size,year of publishment,and data source of obesity.The funnel plots and Egger’s test showed no publishment bias,and sensitivity analysis showed stability of the results.(3)The systematic review of BMI and quality of life showed that there were 15 studies met the inclusion criteria and 8 studies were included in meta-analysis.The combined WMD(95%CI)for underweight,overweight and obesity were-0.65(-1.63,0.34),-0.75(-1.03,-0.43)and-2.28(-2.68,-1.87)in physical component summary(PCS)seperately,and-1.54(-2.02,-1.07),1.09(0.78,1.40),and 0.30(-0.12,0.71)in mental component summary(MCS).There was heterogeneity among the researches included and might mainly resulted from different classifications of BMI and age of participants.No publishment bias was showed.Sensitivity analysis and the results excluded the studies with heterogeneity showed a stability of results.(4)Results of the cross-sectional study on the association between BMI and quality of life showed:BMI was non-linearly related to quality of life,and the results among the WHO,Asian and Chinese classifications were similar.With more confounders adjusted,the results were more similar.Overall,PCS in normal weight was the highest without adjustments,and overweight and obesity impaired the PCS.After the confounders adjusted,PCS in overweight and obesity was not lower than that in normal weight.MCS in overweight and normal weight substantially higher than normal weight especially in overweight.Both PCS and MCS were impaired in underweight.There were different patterns for quality of life in different ses and age.Conclusion:(1)The amount of studies on obesity paradox increased rapidly.Lavie,CJ was the most productive author and American was the most procuctive country.Most of the studies were published on juornals of cardiovascular diseases.The subjects were mainly patients with cardiovascular diseases and with an older age.(2)Underweight has a higher mortality and lower quality of life.Overweight has a lower mortality and higher quality of life.Obesity has a better quality of life in MCS,and there was no significant difference of quality of life in MCS between obesity and normal weight.The results of this study support the obesity paradox.(3)There were a little differences of the results anong different BMI classifications with a totally similar trend.