Background: Hospitalization among older people is common and associated with risk of adverse outcomes such as iatrogenic disorders and physical impairments. Knowledge about personal characteristics and social factors related to hospitalization is scarce. In order to understand which factors that are related to hospitalization risk, a prospective study with a multifactorial approach was conducted.

Methods: In 2003, 794 Swedish persons (mean age 70.1 years, 60.7% females) answered a postal questionnaire as a part of the population-based longitudinal Swedish Adoption/Twin Study of Aging (SATSA). Participants were asked about physiological and psychological health, personality and socio economic factors. During seven years of follow-up, information on hospitalizations and the associated diagnoses were obtained from the Swedish National Inpatient Register.

Results: Preliminary results show that 484 persons (61.0%) had at least one hospital admission during the follow-up period. The most common causes of admission were cardiovascular diseases and tumors. Cox proportional hazard regression model controlling for age, sex and dependency within twin pairs, showed that higher locus of control (HR=0.89, 95% CI=0.83-0.96), marital status (widow/widower (HR=0.64, 95 % CI=0.50-0.81) and unmarried (HR=0.67, 95% CI=0.50-0.90)), and support from friends (HR=0.93, 95% CI=0.87-0.99) were associated with lower risk of hospitalization, while greater numbers of diseases (HR=1.11, 95% CI=1.03-1.20) and negative life events (HR=1.16, 95%  CI=1.00-1.34) were associated with increased risk of hospitalization.

Discussion: Our results show that both personal and social factors were important for the risk of hospitalization. This might be used in future interventions for understanding health care utilization.