Data for: Prophylactic Effect of Sulfasalazine against Pneumocystis Pneumonia in Patients with Rheumatoid Arthritis: A Nested Case-Control Study

"MATCHED_STUDY" includes the data on PJP cases and their corresponding matched controls.
"NONMATCHED_STUDY" includes the data on PJP cases and their corresponding non-matched controls (just matched on recorded years).
The description of variables are explained in the files.

“MATCHED_STUDY”包含关于PJP病例及其对应的匹配对照的数据。 “NONMATCHED_STUDY”则包含关于PJP病例及其对应的非匹配对照的数据（仅匹配于记录年份）。变量的描述详见文件。