Statistical Analysis
Patient-reported surveys were scored according to the scoring guides of
the individual test developers, including methods for handling any
missing data. The CCSS-NCQ was scored by calculating a total raw score
for each of the 4 domains, then converted to a Z-score using a healthy
comparison group as reference, with higher Z-scores corresponding to
worse neurocognitive scores.19 Responses for the
Neuro-QoL were summed as total raw scores and converted to standardized
T-scores with a mean score of 50 and a standard deviation of 10 using
the general U.S. population as reference, with lower T-scores suggesting
lower cognitive quality of life.21 The PROMIS Sleep
Short Form 4a was summed as a total raw score and then translated into a
T-score with a mean of 50 and a standard deviation of 10 based on the
general population, with higher T-scores signifying worse sleep
quality.22 Hearing issues were defined as
self-reported moderate/severe hearing trouble or deafness, current use
of hearing aid, or moderate/severe tinnitus.
Descriptive statistics including frequency distributions and medians and
IQR (interquartile range) were calculated for demographic and treatment
variables. Primary outcome variables, including individual CCSS-NCQ
domain and Neuro-QoL scores, were further dichotomized into 2 groups
based on perceived clinical impairment. Consistent with previous
studies, impairment was defined as Z-score >1.28 for the
CCSS-NCQ (corresponding to the worst 10th percentile
of scores based on healthy control age-adjusted
norms)19 and T-score <40 for the Neuro-QoL
(corresponding to 1 SD below the standardized mean).24Scores were compared using chi-squared test for categorical variables
and analysis of variance or t-tests as appropriate for continuous
variables. To assess the potential influence of non-responders on the
reported group averages, we also applied inverse probability sampling
weights accounting for sex, age at HCT, and current age of the entire
eligible population. Finally, the strength of the associations between
certain clinical features and impairment on the CCSS-NCQ or Neuro-QoL
were examined using multivariable logistic regression and reported as
odds ratios (OR) with 95% confidence intervals (95% CI). The models
for risk of neurocognitive impairment included dichotomized co-variates,
defined as presence or absence of age <10 years at HCT,
hearing issues, stroke/seizures, and sleep impairment adjusted for each
other, as well as sex and current age. Other potential co-variates were
examined but ultimately not included in the multivariable models. All
analyses were completed using Stata (Version 16, StataCorp, College
Station, TX).