Atrial fibrillation (AF) increases the risk of stroke, is associated with increased stroke severity, and is the main cause of stroke in elderly participants who receive Medicare.^1,2 Medical costs for AF and stroke have been estimated separately,^3–5 but there is little information on the costs associated with AF among stroke patients. While AF is relatively rare in the general population, it is much more common among patients hospitalized for stroke because of its powerful role as a risk factor. As such, AF-specific costs among the stroke population could play a substantial role influencing the overall costs of stroke care. Such costs would be critical for evaluating the cost-effectiveness of stroke interventions, especially those involving patients with AF, and thus we investigated hospitalization costs associated with AF for stroke patients in an elderly population.

We identified 226 289 stroke hospitalizations, with 42 557 (19.1%) having a diagnosis of AF (or atrial flutter) (Table 1). The proportion of hospitalizations having AF increased with age from 12.4% for those aged 65–74 years to 26.0% for those aged 85 or older. The proportions of AF among hospitalizations for women and white patients were higher than for their comparison groups. In contrast, the proportions were similar for initial admissions and readmissions, (18.8% for both). Overall, mean per-admission costs were $27 915 ($28 843 for AF admissions and $27 700 for admissions without AF).

After controlling for many potential confounders, AF increased the cost of hospitalization by $2711 (9.4%; P<0.001) (Table 2). Age was inversely associated with per-admission cost. AF increased the costs by $3159, $2610, and $2197 for patients aged 65–74, 75–84, and ≥85 years, respectively. Compared with women, men had a higher per-admission cost but a lower AF-associated cost ($2481 versus $2865). LOS was significantly and positively associated with per-admission costs, while for costs associated with AF increased with LOS up to $5888 for hospitalizations with an LOS of 14–29 days.

Initial hospitalizations cost $12 354 more than readmission, and AF increased the cost by $2844 for initial hospitalizations and $1735 for readmissions. Admissions in which the stroke was primary had a lower per-admission cost than those in which it was not primary, but the AF-associated cost was higher for primary than non-primary strokes. Per admission, intracerebral hemorrhage (ICH) cost $10 101 more than non-ICH, but the cost associated with AF was higher for non-ICH strokes ($2757) (AF did not significantly increase the cost for ICH stroke).

Our study may be the one of the first describing the impact of AF on hospitalization costs among stroke patients using a large dataset. We found that AF increased the cost of stroke hospitalizations after controlling for health status and other potential confounders. This finding confirms the fact that stroke with AF is more severe than stroke without this disorder.²

Our findings that younger patients had both higher costs per stay and higher AF-associated costs than older patients and that men had a higher cost per hospitalization but that women had higher AF-associated costs should be useful for developing stroke prevention programs that incorporate the prevention or management of AF. Improved prevention of AF in younger patients and women might produce cost savings, although that would have to be formally tested. Our finding that AF-associated costs were higher for hospitalizations with longer LOS invites efforts to improve AF management for stroke patients with longer LOS while also perhaps achieving economic efficiencies.

The finding that both per-admission costs and AF-associated costs were higher for initial admissions than readmissions was a bit surprising, especially as an earlier investigation found that recurrent strokes had poorer outcomes on average than first strokes.⁷ We also found that primary stroke cost less than non-primary stroke but had higher AF-associated costs. ICH had much higher costs than non-ICH stroke, but AF-associated costs for ICH patients did not differ significantly from those for such patients without AF, while such costs for non-ICH strokes were significantly greater. These findings suggest that evaluations of the cost-effectiveness of stroke programs should consider stroke admission type (initial or readmission), diagnosis status (primary, not primary), and event type (ICH or no-ICH) among AF patients.

Our study had several limitations including: 1) As with all studies that rely on medical records, the issue of coding error must be considered. Although misdiagnosis issues have been investigated in the literature, how this issue would affect the costs in our study is unknown. 2) Our study sample consisted entirely of Medicare beneficiaries, and thus the cost might be influenced by the Medicare reimbursement rate. 3) We did not incorporate the impact of anticoagulant therapy and in-hospital mortality in the cost analysis. Regardless of these limitations, however, the fact that we used a large sample and analyzed the costs from different angles suggests that our findings should have great utility and wide applicability.

This study indicated that the high costs of stroke hospitalizations can be expected to vary by demographic variables, admission status, LOS, and stroke type. Furthermore, we found that AF increases costs for a wide variety of patients. The detailed cost information on stroke patients presented here could be used in the development of cost-effective programs for stroke prevention, especially among AF patients. Further information is needed on the costs in patients with AF who are taking anticoagulants.