Table 3.

Adjusted covariates in studies included in the meta-analysis

Study	Adjusted covariates
Chung 2016	Age, sex, urbanization, salary, location
Lee 2014	Age, sex, drinking status, comorbidities of esophageal malignancy
Nwizu 2017	Age, education, geographic location, tobacco consumption, family history of malignant tumors, exercise habit, secondhand cigarette smoke, drinking status, fruit and vegetable intake
Michaud 2018	Age, location, educational status, alcohol consumption, blood glucose level, BMI, race, smoking behaviors
Mai 2016	Age, oral hygiene habits, family history of malignant tumors, educational status, tobacco consumption, secondhand cigarette smoke, body mass index
Michaud 2008	Age, frequency of exercise, BMI, energy intake, dietary collocation, drinking status, tobacco consumption, blood glucose level, smoking behaviors, calcium supplement, residence, race
Michaud 2016	Age, drinking habit, tobacco consumption, height, frequency of exercise, BMI, residence region
Arora 2010	Age, gender, blood glucose level, tobacco consumption, tobacco consumption of partner, drinking behavior, BMI, vocation, education
Lee 2017	Age, sex, family economic status, location, cardiovascular and cerebrovascular diseases, physical activity, drinking habit, tobacco consumption
Ahn 2012	Sex, age , ethnic origin, smoking status, education

BMI: Body mass index.