Disease burden can be measured in many ways. This is particularly important for AORC, which has a modest effect on conveniently measured outcomes like mortality, but a much larger impact on less conveniently measured outcomes important to functionality for most people. Such outcomes include effects on work, health-related quality of life, independence, and ability to keep doing valued life activities. Three of these burdens, along with adverse life style factors that are associated with arthritis, are addressed in the estimates below.

Bed Days and Lost Work Days

Bed Days

Bed days are defined as spending one-half or more days in bed due to injury or illness, excluding hospitalization. Data are averaged over three years for the NHIS to achieve larger, more powerful sample sizes. For the years 2013-2015, the proportion who had bed days among adults with arthritis was higher than that for adults with any medical condition (45% vs. 41%). The 24.6 million adults with doctor-diagnosed arthritis and any bed days, 10% of the adult population, had an annual average of nearly 25 days spent in bed in the previous 12 months. This is far higher than the annual average of 14.5 bed days for the 41% of adults with bed days for any medical condition. Multiplying the 24.6 million adults by the mean bed days for arthritis resulted in 607 million bed days overall, or 55% of the 1.1 trillion bed days among adults reporting any medical condition. (Reference Table 3A.4.1.1 PDF CSV)

Among adults with arthritis, females had a higher proportion than males of bed days (48% vs 41%) and a slightly higher mean number of days (25.6 vs. 23.1 days).  Females with arthritis accounted for 65% of total bed days in 2013-2015.  (Reference Table 3A.4.1.1 PDF CSV)

Bed days are reported by a higher proportion of younger than by older adults with arthritis. Adults with arthritis had a higher proportion with bed days than adults reporting any medical condition in each age group: persons aged 18 to 44 years (59% vs. 46%), aged 45 to 64 years (50% vs. 41%), and aged 65 and older (35% vs. 31%).  This was also true for the average number of bed days: 18 to 44 years (20.1 vs 9.3 days), 45 to 64 years (26.4 vs. 17.3 days), and 65 and older years (24.7 vs. 22.0 days). (Reference Table 3A.4.1.2 PDF CSV)

Among racial/ethnic groups, those with arthritis had similar proportions reporting bed days (range 43%-47%) and a similar average number of bed days (range 21.4-25.6). (Reference Table 3A.4.1.3 PDF CSV)

In the different geographic regions, those with arthritis had similar proportions with bed days (range 43%-47%) and a similar average number of bed days (range 22.4-27.2). (Reference Table 3A.4.1.4 PDF CSV)

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Lost Work Days

Persons in the workforce are defined as adults having worked at a job in the past 12 months. In the 2013-2015 NHIS sample, 81% of those age 18 to 44 held a job (56% of workforce), 74% of persons aged 45 to 64 years held a job (38% of workforce), and 20% of persons aged 65 and older were still working, comprising just under 6% of the workforce. Among the persons aged 65 and older, 83% were age 74 and younger. By sex, 73% of males reported being in the workforce, while 62% of females worked in the past 12 months. Males represented 52% of the workforce.

Lost work days for persons in the workforce are defined as absence from work due to illness or injury in the past 12 months, excluding maternity or family leave. For the years 2013-2015, the proportion of persons who had lost work days among adults with arthritis was lower than that for adults with any medical condition (23% vs. 30%).  Among adults with doctor-diagnosed arthritis, 12.6 million in the workforce reported an average of 14.3 work days lost in the past 12 months, nearly 5 days more than the 9.4 work days reported by adults with any medical condition. This resulted in 180.9 million total lost work days among adults with arthritis who are in the workforce, or 34% of the 533.2 million work days lost among adults reporting any medical condition.

Among adults with arthritis, females and males in the workforce had similar proportions with lost work days (23%-24%) and similar mean number of lost work days (14.2-14.4).  Females accounted for 57% of total arthritis-attributed lost work days per year in 2013-2013 due to the higher number of females with arthritis. (Reference Table 3A.4.1.1 PDF CSV)
 
Compared with older adults, younger adults with arthritis or any medical condition had a higher proportion of lost workdays.  Adults with arthritis had a higher proportion of lost work days than adults reporting any medical condition for persons aged 18 to 44 years (47% vs. 42%), but proportions were similar for the older age groups. Although, overall, the proportion of persons with DDA reporting lost work days was slightly less than was reported for any medical condition, the average number of lost work days was higher among adults with arthritis than adults with any medical condition: 18 to 44 years (13.4 vs 8.2 days), 45 to 64 years (14.6 vs. 10.8 days), and 65 and older (15.3 vs. 12.6 days).  Adults aged 45 to 64 accounted for 62% of total arthritis-related lost work days even though they only comprised 38% of the workforce and 47% of those with any medical cause. (Reference Table 3A.4.1.2 PDF CSV)

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Activity Limitations

Activity limitations are included in the National Health Interview Survey in both the family database and the adult database, with slightly different response codes. Respondents are asked first if they need help performing a variety of activities of daily living (ADL), such as personal care, bathing, eating, getting in/out of chair, and walking. They are also asked if they are “limited in the kind or amount of work” they can perform. If a limitation of any type has a “yes” response, respondents are shown a list of 34 possible medical conditions and asked to identify those that cause the limitation. Multiple causes may be identified. This section uses the adult database and focuses on cases where arthritis is identified as a cause of limitations. The variable AAAL, defined in the introduction to this arthritis section, is based on a single question in the NHIS1 and produces somewhat different numbers than this more inclusive definition of activity limitations.

Limitations in any activities of daily living (ADLs) include seven components.  Musculoskeletal-related ADLs include only the three limitations related to movement and action commonly associated with musculoskeletal diseases and are 1) “needing help with routine needs,” 2) ”needing help with personal care,” and 3) “having difficulty walking without equipment.” Other ADLs are related to memory, vision, hearing, and other limitations.

Of the 35.6 million adults with limitations in any ADL, 23% (8.0 million) named arthritis as a cause; the proportion jumped to 29% for those with a limitation in musculoskeletal-related ADLs. One-third (33%, 4.5 million of 13.9 million) of adults with difficulty walking identified arthritis as a cause. More than 1 in 4 attributed their need for help with routine needs (2.8 million) or personal care (1.5 million) to arthritis. (Reference Table 3A.4.2.1 PDF CSV)
 
These numbers demonstrate the large impact of arthritis on adults with limitations in any ADL or in musculoskeletal related ADLs. The effect was much stronger among females than males (Reference Table 3A.4.2.1 PDF CSV) and among older adults. (Reference Table 3A.4.2.2 PDF CSV)

Little difference was found between adults by race/ethnicity except for slightly higher proportion of non-Hispanic blacks attributing limitations to arthritis. (Reference Table 3A.4.2.3 PDF CSV). Geographic region in the US does not seem to be a factor. (Reference Table 3A.4.2.4 PDF CSV)

Work limitations are defined here as those unable to work now due to health or limited in kind or amount of work (i.e., “unable to work” or “limited in work”). Of the 28.1 million adults with work limitations per year in 2013-2015, arthritis attributable work limitations (AAWL) affected on average 23% (6.4 million).  Among those with any medical condition limiting work, 23% attributed their inability to work now to arthritis, while 22% limited in kind or amount of work did so. Higher percentages of females and older workers identified arthritis as a cause for work limitations. There was little difference seen by race/ethnicity or geographical region. (Reference Table 3A.4.2.1 PDF CSV; Table 3A.4.2.2 PDF CSV; Table 3A.4.2.3 PDF CSV; and Table 3A.4.2.4 PDF CSV).

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Quality of Life and Lifestyle Factors

Among persons with DDA, compared with those without DDA, Health-Related Quality of Life (HRQoL) is worse on several scales. When assessed by self-reported health status, 27% of those with DDA reported fair/poor health compared to 12% of those without DDA. The DDA group also reported a higher mean number of days in the past month with poor physical health (6.6 vs 2.5 days), poor mental health (5.4 vs 2.8 days), or days with limitations in usual activities (4.3 vs 1.4 days).2 Using the same “unhealthy days” measures, an analysis of 2014 Humana Medicare Advantage members found that those with arthritis had more total unhealthy days, by 2.2 days per year, than those without arthritis, and that comorbid arthritis associated with hypertension, diabetes, chronic obstructive pulmonary disease, and congestive heart failure resulted in significant increases in both physically and mentally unhealthy days.3
 
The prevalence of DDA and of AAAL is much higher among those with the adverse lifestyle factors of obesity, insufficient or no physical activity, and fair/poor self-rated health.4 (Reference Table 3A.4.3 PDF CSV)

• 1. National Health Interview Survey 2013-2015. Question: “Are you limited in any way in any of your usual activities because of arthritis or joint symptoms?” https://www.cdc.gov/nchs/nhis/nhis_questionnaires.htm.
• 2. Furner SE, Hootman JM, Helmick CG, Bolen J, Zack MM. Health-related quality of life of US adults with arthritis: analysis of data from the Behavioral Risk Factor Surveillance System, 2003, 2005 and 2007. Arthritis Care Res 2011;63(6):788-799.
• 3. Havens MA, Slabaugh SL, Helmick CG, et al. Comorbid arthritis is associated with lower health-related quality of life in older adults with other chronic conditions, United States, 2013-2014. Prev Chronic Dis 2017;14:160495. DOI: https://doi.org/10.5888/pcd14.160495.  https://www.cdc.gov/pcd/issues/2017/16_0495.htm  Accessed September 8, 2017.
• 4. Barbour KE, Helmick CG, Boring M, Brady TJ. Vital signs: prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitation — United States, 2013–2015. MMWR 2017;66:246–253. DOI: http://dx.doi.org/10.15585/mmwr.mm6609e1.