Response to Letter to the Editor on "Chronic Phase Survival Rate in Stroke Patients With Severe Functional Limitations According to the Frequency of Rehabilitation Treatment"

Abstract

To the Editor, We appreciate the readers’ interest in and discussion of our recent study. In a previous letter, the authors expressed concerns about insufficient covariates to conclude whether our results were reliable. They were concerned about potentially fatal conditions such as sepsis, pneumonia, and hip fracture, which could make receiving rehabilitation treatment difficult.

To reduce the immortal time bias using landmark analysis, we considered the following methodology: we excluded patients who died within 2 years of stroke onset from the chronic phase survival analysis. Given the time-varying characteristics of the frequency of rehabilitation treatments, the time point of 2 years after onset served as a landmark. The fatal conditions presented are major risk factors that increase mortality in the early stage of stroke.1,2 A previous report revealed a 1-year mortality rate of 2.1%-34.3% after stroke.3 Our findings revealed that among 10,826 patients in the initial cohort, 3555 (32.8%) patients died within 2 years after stroke onset.4 Therefore, by excluding patients who survived at least 2 years after stroke onset, we were able to sufficiently exclude the early effects of fatal complications that the National Health Insurance Service (NHIS) database could not capture.

An additional question was whether these patients survived despite fatal complications but did not receive rehabilitation treatment while in intensive care. The most notable finding of our study was that the group with severe disabilities received more rehabilitation treatment than other groups. If there were many cases wherein the condition to receive rehabilitation treatment for fatal complications was not met, the frequency of rehabilitation treatment would not have differed according to the severity grade, rather, patients with a National Disability Registration (NDR) grade of 3 should have shown a higher rehabilitation treatment frequency than those with an NDR grade of 1 (the most severe disability grade). However, our findings suggested that patients in the higher severity group received adequate rehabilitation treatment. The specialized rehabilitation treatment (claim code: MM105) that we used as a variable of interest in this study was defined as being professionally performed 1-on-1 treatment for patients with central nervous system lesions and the treatment lasting for 30 minutes. However, this code is not prescribed differently based on stroke severity or comorbidity. Therefore, even patients with fatal diseases can receive 1-on-1 rehabilitation treatment tailored to their specific needs. Furthermore, because this specialized rehabilitation treatment universally covers 2 years after stroke onset under the NHIS system in South Korea, most patients can easily access rehabilitation treatment at a low cost. Furthermore, stroke adequacy evaluation items in South Korea assess whether early rehabilitation is implemented.5 Thus, patients with conditions such as nonfatal pneumonia or hip fracture may benefit from specialized rehabilitation treatment involving bed or wheelchair transfer.

Therefore, we propose that our study reduced the effect of early fatal conditions on the frequency of receiving rehabilitation treatments after stroke onset by employing a methodological approach and taking into consideration the unique environment in post-stroke rehabilitation treatment under the NHIS system of South Korea.