Disability as a Function of Disease Duration
Tuula Tyry, PhD, MAED, Program Manager, NARCOMS Project— Barrow Neurological Institute, St. Joseph’s Hospital, Phoenix, AZ
Introduction
The NARCOMS MS Patient Registry continues to grow and, as of June 2004, has over 24,000 active participants. Online participation has climbed to 66%, which is a much appreciated and cost-saving trend that we hope will continue. In this NARCOMS report we address the registry participants’ self-assessed disability and performance levels in nine functional areas. Special emphasis is given to the oftenoverlooked symptoms reported by those in the lower range of the mobility-oriented Patient Determined Disease Steps (PDDS) scale. We also relate performance levels and PDDS scale scores with years of disease duration divided into four groups: less than 5, 5 to <10, 10 to <20, and >20 years.
Demographics
The analysis is based on the 8,583 responses received during the Fall 2003 update survey. In this cross-sectional cohort, women outnumbered men almost 3 to 1, as 73% were women. Table 1 presents a breakdown of background information separately for women and men based on duration of the disease. On average, the women were younger (50.0 + 10.4 years) than men (54.6 + 10.9 years). Slightly less women (59%) than men (61%) had a college education. The percentage of those employed full-time or part-time decreased across the disease duration groups (those in less than 5 years compared to those in more than 20 years), from 57% to 19% in women and from 57% to 17% in men. On the average, women were more likely to work than men (38% vs. 30%) but less likely to have health insurance (75% vs. 87%).
While the percentage of women with insurance remained relatively constant across the disease duration levels, the corresponding percentage increased for men. This is partially due to the more common VA insurance coverage among the older male Generation: 7% of men in the over-20 years of disease group had VA health coverage while only 1% of the women in the corresponding group reported the same. Half or more of the men in each of the disease duration groups carried private insurance with at least one company. In women, this was seen only in the first two duration groups, possibly indicating a higher level of insurance coverage among the younger generation.
The impact of disease duration on income appeared to be different for women and men. The lowest percentage (62%) of women with household income over $30,000 was in the group with over 20 years disease duration, while the corresponding lowest percentage (67%) for men was seen in the 5 to 10 years of disease duration. These differences likely reflect the typical later onset and more severe progression of the disease observed in men and subsequent accelerated impact on employment decisions and income potential.
PDDS Scores
The Patient Determined Disease Steps (PDDS) scale is a self administered Disability assessment for people with MS. Similar to the clinician administered Expanded Disability Scale (EDSS) the PDDS 8-point scale focuses mainly on walking ability. Table 2 presents a breakdown of the PDDS scores for women and men based on disease duration since diagnosis. The median PDDS score was 4 for women and 5 for men. In other words, half of the women reported a disability level of early cane or milder, while half of the men had not experienced disability levels beyond late cane. However, a majority (60%–80%) of men required assistive devices for walking from the disease duration group of 5 to 10 years on. For the majority of the women, similar assistance was not required until 10 to 20 years of disease duration.
At the other end of the PDDS spectrum, the combined percentage of normal, mild, and moderate disability declined gradually from 59% to 16% by 20+ years of disease duration in women and from 46% to 12% in men. This indicates that, even after 20 years of disease, well over 10% of people had no limitations in their walking ability. Increasing that percentage through early active management of the disease to slow progression is one of the primary objectives of contemporary MS care. The next section focuses on other functional aspects of daily living often affected by MS.
Performance Scale Profiles
The nine performance scales used in each update survey describe some of the different kinds of disabilities people with MS may have, including problems associated with mobility, upper extremity function, vision, fatigue, cognitive symptoms, bladder/bowel function, sensory function, spasticity, and pain. Although the scores on all of these scales tend to go up during the course of the disease, it is important to keep in mind that the rate and timing of changes can be quite different. Since each scale measures symptoms affecting the person’s quality of life, it is useful to consider the performance scale scores in addition to the PDDS or the clinician-administered EDSS scores when assessing the overall impact of MS.
As seen in Figure 1, the average profiles for disability associated with fatigue, cognition, and pain share a somewhat similar pattern. Unlike the steadily increasing self-assessed disability caused by mobility, bladder/bowel dysfunction, hand disability, and spasticity syndromes, or the relatively stable profile between levels 2 and 7 for sensory function and vision, this pattern spikes at level 2 on the PDDS scale. The pattern of the curve suggests that on the average, despite only moderate disability in terms of gait, people at this level appear to experience frequent fatigue forcing them to change some of their activities, have occasional memory problems or confusion affecting some of their activities and are occasionally forced to change some of their activities. Addressing these areas of functionality plays an essential role in the overall management of MS.
Discussion and Future Research
This brief analysis of the Fall 2003 NARCOMS survey data demonstrates the impact of disease duration on disability and performance levels and describes some of the associated changes in the socioeconomic status of people living with MS. Fatigue, cognitive problems, and pain emerged as some of the crucial elements of disability experienced in association with relatively early stages of gait impairment. Further analyses are already under way to address the role of various performance measures in assessing the overall disease burden and to reveal their association with socioeconomic changes. The impact of various treatment regimens on quality of life is also being investigated. The expanding size of the NARCOMS MS Patient Registry will allow researchers to identify prominent disease and treatment patterns and estimate their impact in increasingly specific subgroups, thus leading to a deeper understanding and more effective management of the disease.
