Fig 1.
Overview of the nested case–control study design.
The Kyoto Claim Database consists of health insurance claims from two major insurance systems: the National Health Insurance and the Japan Health Insurance Association. The National Health Insurance (database 1) includes self-employed individuals, retirees, and their families from April 1, 2013, to March 31, 2023. The Japan Health Insurance Association (database 2) covers owners and employees of small- and medium-sized businesses and their families from April 1, 2015, to March 31, 2023. The index month was defined as the month of the first CVD event for cases, or a randomly selected month within the observation period for controls. A 3-year time window preceding the index month was used for exposure assessment. CVD, cardiovascular disease; AD, atopic dermatitis.
Table 1.
Characteristics of CVD Cases.
Table 2.
Characteristics of cases and matched controls in the main analysis.
Fig 2.
Of the 78,196 patients with a first CVD event in the databases (IHD, n = 40,864; stroke, n = 39,130), 2,757 individuals (IHD, n = 1,247; stroke, n = 1,563) were aged 40–59 years at the index month and had at least 3 years of prior observation. Of these, 2,672 were matched with 26,720 controls using eight predefined matching factors for the main analysis. CVD, cardiovascular disease; IHD, ischemic heart disease.
Fig 3.
Distribution of practice months among cases and controls.
The figure illustrates the distribution of the number of practice months during the observation period for cases and controls. Compared with controls, cases tended to have fewer practice months. Median (interquartile range) practice months were 29 (16–46) for cases and 55 (33–79) for controls.
Table 3.
Comparison of AD characteristics between cases and matched controls in the main analysis.
Table 4.
Comparison of AD characteristics between cases and matched controls in the main analysis (Continued).