The prevalence and rate of cognitive impairment is no greater in older adults with arthritis than their non-arthritic counterparts, according to a study recently published in Rheumatology International.1

To determine the prevalence of cognitive impairment (cognitive impairment but not dementia [CIND] and dementia) in older adults with arthritis and the cross-sectional association between arthritis and cognitive impairment in that population, Nancy Baker, ScD, MPH, OTR/L, of the School of Health and Rehabilitation Sciences at the University of Pittsburgh, and colleagues analyzed data from the Health and Retirement Study (HRS). HRS is a longitudinal study of health and economic well-being based on interview data from approximately 20,000 US adults older than 50. Every 6 years, HRS adds a new cohort of adults age 51 to 56. Data are collected from the study population every 2 years.

The investigators confined their research to adults age 65 and older from the 2004 to 2010 cohort, excluding adults with cognitive impairment at baseline. Data from 9728 individuals were ultimately included. The investigators identified cases of CIND and dementia by analyzing data from a short battery of tests — included in the HRS — that measure short-term memory, long-term memory, working memory, attention, and processing speed. The HRS question “Have you ever had, or has a doctor ever told you that you have, arthritis or rheumatism?” was used to identify individuals with arthritis.

Results showed no statistically significant differences in the unadjusted prevalence of CIND and dementia in older patients with or without arthritis (CIND: 20.8%, 95% CI 19.7-21.9 vs. 18.3%, 95% CI 16.8-19.8, respectively; dementia: 5.2%, 95% CI 4.6-5.8 vs. 5.1%, 95% CI 4.3-5.9, respectively). When results were adjusted for demographic, socioeconomic, and medical covariates (age, sex, marital status, education, body mass index, number of chronic medical conditions, smoking status, the presence or absence of depression, and frequency of physical activity), the association was still statistically insignificant (CIND incidence density ratio: 1.6, 95% CI 0.9-2.9; dementia incidence density ratio: 1.1, 95% CI 0.4-3.3). Study participants with and without arthritis developed CIND or dementia at similar rates over 6 years, suggesting that the development of cognitive impairment is not accelerated in the presence of arthritis.

Several previous studies had concluded that arthritis and cognitive impairment were associated.2–6 However, Dr. Baker and colleagues pointed out several methodological issues that could account for the difference in results. In addition to being derived from specialized databases and registries less representative of typically aging adults, previous research had not controlled well for the variables that could explain reduced cognition, including pain, depression, and physical activity. Wrote Dr. Baker and colleagues: “studies that reported associations between cognitive impairment and arthritis may have been affected by sequelae associated with arthritis.”

Summary & Clinical Applicability

“While my research does not demonstrate a significant difference between groups, it is important to note that the prevalence of cognitive impairment [with] no dementia was slightly higher in those with arthritis, which may suggest that some subgroups of people with arthritis may indeed be at greater risk for mild cognitive impairments,” Dr. Baker said in an email interview with Rheumatology Advisor

“Large samples of people who have their type of diagnosis accurately ascertained should be examined to see if there is a different risk for different types of arthritis. Of equal importance is the ability to identify why people with arthritis experience cognitive limitations,” she added. “Thus, we need to understand better how sequelae of arthritis, such as pain and depression, affect cognition and ensure that treatment of arthritis addresses these to help prevent cognitive issues.”

Limitations

  • A lack of objective testing and diagnosis of cognitive impairment or arthritis
  • Arthritis was not differentiated by type
  • Participants who required proxies to provide answers were excluded
  • 36% of study participants were lost to follow-up
  • The method used to identify levels of physical activity has not been validated

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References

  1. Baker NA, Barbour KE, Helmick CG, Zack M, Al Snih S. Arthritis and cognitive impairment in older adults [published online March 23, 2017]. Rheumatol Int. doi:10.1007/s00296-017-3698-1
  2. Lu K, Wang H-K, Yeh C-C, et al. Association between autoimmune rheumatic diseases and the risk of dementia [published online April 30, 2014]. BioMed Res Int. 2014;2014:861812. doi:10.1155/2014/861812
  3. Shin SY, Katz P, Wallhagen M, Julian L. Cognitive impairment in persons with rheumatoid arthritis. Arthritis Care Res. 2012;64(8):1144-1150. doi:10.1002/acr.21683
  4. Appenzeller S, Bertolo MB, Costallat LT. Cognitive impairment in rheumatoid arthritis. Methods Find Exp Clin Pharmacol. 2004;26(5):339-343.
  5. Wallin K, Solomon A, Kåreholt I, Tuomilehto J, Soininen H, Kivipelto M. Midlife rheumatoid arthritis increases the risk of cognitive impairment two decades later: a population-based study. J Alzheimers Dis. 2012;31(3):669-676. doi:10.3233/JAD-2012-111736
  6. Huang S-W, Wang W-T, Chou L-C, Liao C-D, Liou T-H, Lin H-W. Osteoarthritis increases the risk of dementia: a nationwide cohort study in Taiwan [published online May 18, 2015]. Sci Rep. 2015;5:10145. doi:10.1038/srep10145