C
ost variables
Indirect and direct costs were estimated from the available NHWS data. Annual indirect costs were calculated by integrating information, from the WPAI-GH, and hourly wage rates, from the Japan Basic Survey on Wage Structure, 2011, using the Lofland method.21,22 For each employed respondent, his or her annual wage was estimated based on median weekly rates (provided by demographic strata) multiplied by the number of work weeks in a year. Direct costs were estimated by multiplying the number of physician visits and hospitalizations by two (to estimate annual number of visits) and then multiplied by the corresponding unit cost for each, which was obtained from Japan’s Ministry of Health, Labour and Welfare (ER visits were not included in the cost calculations as with the exception of the use of an ambulance,