FIGURE 1.

Flowchart of the study population selection. *Severe diseases include myocardial infarction, congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia, chronic pulmonary disease, connective tissue disease, liver disease, diabetes mellitus (with or without chronic complications), hemiplegia, moderate or severe renal disease, any tumor, leukemia, lymphoma, and acquired immune deficiency syndrome. IBD, inflammatory bowel disease; IBS, irritable bowel syndrome.