Dealing with Statistical Challenges in Analysis of SFU-FLIP Study Data
Supervisor: Joan Hu

A promising strategy for reducing the incidence and severity of fall-related injuries in long-term care (LTC) is to decrease the ground surface stiffness, and the subsequent forces applied to the body parts at impact, through installation of compliant flooring that does not substantially affect balance or mobility (Lachance et al, 2016). The flooring for injury prevention (FLIP) study at SFU (Lachance et al, 2016) is a 4-year, parallel-group, 2-arm, randomised controlled superiority trial of flooring in 150 resident rooms at a LTC site. The study’s primary objective is to determine whether compliant flooring (intervention) reduces serious fall-related injuries relative to control flooring and the primary outcome is serious fall-related injury due to a fall in a study room. The study team plans to complete its primary data analysis by April 2018.

This NSERC USRA project (May 2018 – August 2018) aims to address the following statistical challenges arising from the study data analysis:

  1. During the study follow-up time, some study rooms had more than one resident. Instead of according to the study’s initial randomization scheme, the new resident moved in following the order of “first come first serve” when a study room became available. This may violate (i) the balance between the two arms in subject demographics by the randomization and (ii) the conventional assumption of independence among subjects.
  2. There were study subjects experiencing multiple injuries, some of which were of the study interest and some not. To make a fully use of the available data, instead of the conventional survival analysis approaches, approaches with recurrent events need to be considered and thus the R functions for survival analyses cannot be directly applied.
  3. Since this is a study with human subjects, not all the non-intervention-related conditions were controlled. There may be competing interventions. Hip protector use, for example, is common at the LTC site and was not altered for the purpose of the FLIP Study. This likely resulted in less serious fall-related injuries. For another example, some subjects did not have the anticipated follow-up time length of 4 years. One of the causes was death during the study follow-up, and this leads potentially to informative censoring for it may reduce the size of vulnerable subject group.