Healthcare Utilization in the Face of Illness and Costs: Evidence from Japan

This study examines how health shocks to individual family members affect healthcare utilization patterns across entire households. We investigate spillover mechanisms such as preventive behavior changes and disease impacts. Using comprehensive Japanese healthcare claims covering the period from 2005-2023, we exploit the quasi-random timing of acute health events to identify causal effects on family members' healthcare utilization. Our identification strategy leverages detailed longitudinal data linking household members over 18 years. We extract dynamic responses from immediate reactions, examining healthcare utilization and preventive care. We find substantial clustering of cardiovascular disease (CVD) diagnoses within families: 22% of family members’ CVD diagnoses occur within the first year following an index case, with the strongest and most immediate responses among spouses and rapid intergenerational effects between parents and children. We also identify preventive screening as a key protective mechanism—family members who undergo health check-ups after an index diagnosis experience a 13-percentage-point reduction in two-year CVD risk. These findings highlight that health shocks generate significant intra-household behavioral responses, with implications for healthcare cost projections, preventive program design, and family-centered policy interventions.