Thirdly, although the results have adjusted for several important confounding factors, there still have many unselected or unmeasured factors, such as socioeconomic variables (e.g., income level, education level, exercise habit, etc.), some clinical biomarkers (e.g., creatinine, c-reactive protein, homocysteine, etc.), and personal history of diseases (e.g., chronic kidney disease). Here, CRP is linked to chronic kidney disease.