Symptom Profiles in Individuals Aging with Post‐Polio Syndrome

To the Editor: Post-polio syndrome (PPS) is a set of complex neuromuscular symptoms that people who survived paralytic poliomyelitis experience.1, 2 Because of the many ways PPS affects symptoms and functioning, developing a profile of aging with PPS that is relevant to planning clinical care requires assessment of multiple domains and use of tools for which national age norms have been developed. Profiles of symptoms and quality of life indicators were constructed using Patient-Reported Outcome Measurement Information System (PROMIS) instruments to compare persons aging with PPS with matched-age group data from the PROMIS U.S. general population norming sample. Community-dwelling individuals with PPS completed a self-report survey in 2009/10. Eligible individuals were mailed the survey (N = 479), and 446 (93%) responded, 445 (99%) of whom were aged 45 and older, constituting the analytical sample used in this study. To decrease response burden, approximately half the sample responded to the depression, pain interference, and sleep-related impairment questionnaires. Additional information about this study can be found in publications based on the same data.3, 4 The symptoms and QOL indicators included in this study were fatigue, pain interference, depression, sleep disturbance, sleep-related impairment, and social roles satisfaction, measured using the PROMIS version 1.0 short forms (www.nihpromis.org).5 Eight items from the PROMIS physical function item bank that are appropriate for wheelchair users were also included. Higher scores on each measure indicate more of the construct being measured. PROMIS instruments were developed using item response theory, and scores are reported on a T-score metric. This metric is anchored to the mean of the PROMIS norming sample, which is representative of the 2000 U.S. Census in terms of age, sex, and race and ethnicity.6 T-scores are transformed such that a score of 50 with a standard deviation (SD) of 10 represents the mean of the PROMIS normative sample (i.e., a score of 40 is 1 SD worse than the PROMIS normative sample). Mean and median scores of this norming sample were calculated according to age group for each domain, allowing for age group score comparisons between the PPS sample and the PROMIS normative sample. The Sign M test of medians was used to compare each age group domain median with the matching PROMIS normative sample age group median. This nonparametric test was used because most of the scores did not meet the assumptions of parametric tests. To account for multiple comparisons, the Holm method of correction was used to adjust the alpha level of 0.05.7 To visually present the differences according to domain and age, the appropriate age group PROMIS mean was subtracted from each PPS age group domain mean T-score, and the mean differences were plotted (Figure 1). Four hundred forty-five individuals with PPS responded to the survey and completed at least one of the PROMIS measures included in the profile analysis. Thirteen were aged 45 to 54, 171 were aged 55 to 64, 172 were aged 65 to 74, and 89 were aged 75 and older. With one exception, for all domains and age groups, individuals with PPS reported higher symptoms, lower satisfaction with social roles and activities, and poorer physical function than the PROMIS normative sample, although not all differences were statistically significant (Figure 1). The largest differences for all age groups were in physical function. Fatigue, pain interference, and satisfaction with social roles and activities were all at least 0.5 SDs worse than the PROMIS normative sample for all age groups, and fatigue was more than 1 SD worse in the oldest group. The profiles of symptoms and QOL indicators constructed in this study are consistent with previous findings that individuals with PPS experience worse function in most areas measured. The differences between the PROMIS normative sample and the PPS sample were clinically significant (difference was at least 5 points, or 0.5 SDs8) for physical function, fatigue, pain interference, and satisfaction with social roles and activities. Some of the variation across age groups and domains could reflect small sample size, unmeasured selection bias, or the effect of variables that were not measured in this study. Of particular importance for geriatrics—it was found that discrepancies between the PPS sample and the PROMIS normative sample were greatest for people aged 75 and older on four important domains: depression, pain interference, fatigue, and satisfaction with social roles and activities. Targeting specific preventive, clinical, and psychosocial care services to individuals with PPS as they age might favorably influence depression, pain, fatigue, and social functioning. Conflict of Interest: None of the authors have financial or other relationships that might lead to a conflict of interest and have no conflict of interest to declare. The contents of this manuscript were developed under a grant from the Department of Education, National Institute on Disability and Rehabilitation Research Grant H133B080024, but those contents do not necessarily represent the policy of the Department of Education, and endorsement by the federal government should not be assumed. Author Contributions: All authors substantially contributed to study concept and design, acquisition of data, analysis and interpretation of data, and preparation of manuscript. Sponsor's Role: The sponsor had no role in the design, methods, subject recruitment, data collection, analysis, or preparation of paper.