The aim of this study was to identify prognostic factors of the 5R-STS test in adult patients with lumbar degenerative disease. There was a positive correlation between height as well as an active smoker status and worse 5R-STS performance. Ability to work fully was associated with better 5R-STS performance. Age, surgical indication, index level of pathology, history of previous spine surgery, history of pain, analgesic drug use, employment type and severity of anxiety & depression symptoms were not significant influencers of the test but were included in the final model due to confounding effects. Gender did not demonstrate a meaningful influence on the test performance.
Similarly to a population of healthy adult individuals, increased height of patients with LDD correlated with worse 5R-STS performance despite the standardized seat of 43cm height.  This agrees with a study on stroke survivors, which showed that seat height lower than knee height increased the 5R-STS  Therefore, the height of a patient with LDD must be taken into account when interpreting the 5R-STS time and ideally the patient should be sat at knee-height level, or height-adjusted test times should be calculated. [18, 19]
Multiple studies demonstrated a significant positive correlation between age and 5R-STS performance in adult individuals, however the participants were often much older than patients from our cohort or categorized into either 20–29 or 80–85 age groups, missing the 48-year mean age of our participants.[3, 6, 15] A more recent study, however, with a mean age of 39 years also identified a significant age-associated increase in 5R-STS in healthy adult individuals which is more suitable for comparison.  In our study of patients with LDD, age was not a significant prognostic factor for 5R-STS performance. A possible explanation for this might be that the greatest incidence of LDD falls between 40–70 years of age limiting opportunities for identifying a significant correlation.  Interestingly, Gautschi et al.  found that unadjusted raw TUG time increased with age in their study of patients with LDH and lumbar stenosis, demonstrating the differences between the various tests for OFI.
It has been previously suggested that increased BMI, increased age and being female are a significant positive prognostic factor for 5R-STS performance in healthy individuals, which is also in agreement with proven risk factors for development of LDD. [14, 24, 31] Contrary to expectations, no such correlation was identified for patients with LDD. It may be theorized that once a symptomatic LDD pathology requiring surgical intervention develops, variation in 5R-STS time is no longer significantly correlated with basic demographic characteristics in contrast to spine-healthy individuals but predominantly influenced by the pathology. 
Interestingly, in this study, mood-related symptoms were not significantly correlated with 5R-STS time measured by EQ5D Depression & Anxiety domain, which is a validated tool for assessment psychological status. [17, 20] Around 40% of patients with LDD reported a presence of depression & anxiety symptoms, yet the 5R-STS was not influenced by them, emphasizing its objectivity.
The third significant predictor of 5R-STS in patients with LDD was full ability to work. The full ability to work encompasses a range of factors including: the physical ability to actually work (degree of OFI), level of experienced pain, pain tolerance threshold, and mental health. In our study, 75% of patients reported using analgesia daily, and nearly 60% experienced spine-associated pain for over half a year. Peters et al.  suggests that individuals that experience pain for more than six months can acquire a higher pain-threshold. If our patient cohort followed that theory, the greater majority would have been able to work. This links to a previous study, which found increased degree of OFI measured by 5R-STS in patients with LDD and high amounts of back pain but not leg pain.  So far, the significance of this finding is unclear, but it may be that within a subgroup of patients with LDD, there are patients with a painless motor component. Most of our cohort suffered from LDH. Currently, the most commonly reported symptoms are radiculopathy, sensory abnormalities and weakness along the distribution of one or more lumbosacral nerves.  In two studies of patients undergoing microdiscectomy for LDH, the presence of severe motor deficits was associated with delayed surgical recovery at more than two months. [30, 33] Identifying a painless motor deficit in LDD using a simple test holds great potential for improved clinical assessment, especially if it influences postoperative outcomes.
A positive correlation was identified between being an active smoker and worse 5R-STS performance in patients with LDD. However, no relationship between smoking status and TUG time was demonstrated in another study of patients with LDD.  The authors, however, did not differentiate between active smokers and ex-smokers, which is a crucial discrepancy given persistent body changes, even years after smoking cessation. [2, 11]
The purposeful variable selection algorithm described by Bursac et al.  was utilised to identify significant prognostic factors of 5R-STS in patients with LDD. This allowed us to also identify which factors may not be significant predictors but may still indirectly influence 5R-STS performance through confounding. Accordingly, variables with confounding effect – such as age, height, surgical indication, index level of pathology, history of previous spine surgery, history of pain, analgesic drug use, employment type and severity of anxiety & depression symptoms - were recognised and ought to be accounted for in future studies of patients with LDD where 5R-STS is used.
One of the first limitations is the uneven distribution of patients among certain subcategories, more specifically indication. Therefore, the results of this study should not be applied to patients with individual spinal pathology but rather provide an overview of prognostic factors for a range of LDD, because of a lack of statistical power for these subgroup analyses. Since LDH was the most predominant indication in this patient cohort -contributing 72.5% of all patients - the results certainly are powerful enough for this specific patient cohort. Further research to identify prognostic factors of 5R-STS time in individual LDD conditions is encouraged.
Presence of other chronic conditions in this study was not clearly reported - this may unknowingly have influenced the 5R-STS performance. However, our exclusion of patients with hip and/or knee prosthetics and walking aids meant that individuals with comorbidities severely affecting their mobility were not included. This is supported by a weak and inconsistent association between presence of medical comorbidities and degree of OFI measured by another objective test, TUG, in patients with LDD. 
In our study, there is no differentiation between physically active and predominantly stationary employment in relation to the ‘working ability’ category. It would seem that patients with LDD and heavy lifting-focused jobs should be more limited in their working ability than e.g. office workers.  However, individuals with sedentary occupations may also be limited by LDD symptoms due to related long-term axial loading and increased disc pressure.[1, 16, 32]
Due to the incidence of LDD in the middle-aged group, another limitation that is challenging to overcome is not fully being able to identify prognostic factors of 5R-STS time in patients with LDD across other individual age groups.
Lastly, patients in this cohort were from a Dutch specialized short-stay clinic and had a diagnosis of LDD eligible for surgical intervention. Therefore, the identified prognostic factors in this study should be applied to patients with advanced LDD. Studies from other geographical areas are encouraged.