By Betty Tran, MD, MSc
Associate Professor of Medicine, Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago
SYNOPSIS: In this observational cohort study drawn from the National Health and Aging Trends Study, social isolation among older adults admitted to the intensive care unit was associated with greater disability burden and higher one-year mortality rates after critical illness.
SOURCE: Falvey JR, Cohen AB, O’Leary JR, et al. Association of social isolation with disability burden and 1-year mortality among older adults with critical illness. JAMA Intern Med 2021;181:1433-1439.
Up to 24% of older, community-dwelling adults in the United States are socially isolated.1 Although the lack of social connections previously has been associated with difficulties in activities of daily living (ADLs), development of frailty, and higher mortality, there have been no studies examining the relationship between social isolation and critical illness recovery.2-4
Survey data from the 2011 cohort of the National Health and Aging Trends Study (NHATS) was linked to Medicare claims data for intensive care unit (ICU) hospitalizations lasting more than one day between 2011 and 2017. Briefly, NHATS is a random sample of adults ≥ 65 years of age drawn from Medicare enrollment with information on demographics, disability status, health conditions, social connections, and living situation; older adults (> 90 years) and non-Hispanic Black individuals were oversampled. Social isolation was scored (0-6; higher scores indicating greater social isolation) based on responses to the NHATS survey during the year most closely preceding ICU hospitalization and corresponded to four core domains of social connectedness: marriage/live-in partnership, contacts with family/friends, membership in religious organization, and other community group participation. The primary outcome was a count of disabilities in seven ADLs following ICU discharge. The secondary outcome was one-year mortality. Analyses were adjusted for age, sex, probable dementia, frailty, hospital length of stay, use of mechanical ventilation, chronic condition count, prehospitalization disability count, and rural residence.
The primary analysis cohort consisted of 648 ICU hospitalizations (from 543 older adults). The median age was 81 years (interquartile range [IQR], 75.5-86.0), 51% were women, and 21% identified as non-Hispanic Black. Most participants had no disabilities at baseline (median 0; IQR, 0-1). For each incremental rise in social isolation score pre-hospitalization, the post-ICU disability count was 7% higher (adjusted rate ratio [RR], 1.07; 95% confidence interval [CI], 1.01-1.15). Older adults with moderate (score 3 of 6) and severe (score 6 of 6) social isolation had a 23% and 50% higher disability burden, respectively, compared to adults with no social isolation (score 0 of 6).
In terms of one-year mortality, each incremental rise in prehospitalization social isolation score was associated with a 14% increase in risk of death in the year following ICU hospitalization. Compared to no social isolation, moderate and severe social isolation among older adults was associated with a 48% and 119% higher risk of death at one year, respectively.
COMMENTARYThis study adds to the growing body of literature highlighting the pivotal role social determinants of health play in clinically important outcomes and the concept that health is a continuum that begins well before a hospitalization for critical illness. Historically, our focus has been on addressing common ICU diagnoses that contribute to poor long-term outcomes, such as sepsis, delirium, acute respiratory distress syndrome, or ICU-related conditions such as prolonged bedrest or excessive sedation. Although how these issues are handled in the ICU certainly can contribute to improved comorbidity and mortality rates, the recognition that prehospitalization health is equally important (if not more important) in determining post-ICU outcomes has been emphasized only recently. For example, factors such as socioeconomic status, pre-ICU functional status, and rates of inpatient healthcare usage prior to an index hospitalization have been associated with long-term cognitive impairment, functional ability to perform ADLs, and mortality.5-7
The finding that greater social isolation was associated with a significant increase in disability burden and mortality after critical illness is intriguing for a number of reasons. First, the association remained significant even after controlling for other vulnerability factors, such as dementia, frailty, prehospitalization disability, and chronic conditions, all of which are non-modifiable. However, the persistence of an association suggests that finding ways to attenuate social isolation in attempts to improve post-ICU outcomes is feasible.
Second, the study findings prompt further investigation into the mechanisms explaining the association between social isolation and poor ICU outcomes. Possible contributors include biologic differences (e.g., increase in systemic inflammatory biomarkers, dysfunctional neuroendocrine changes), healthcare access (e.g., inability to travel to physical therapy, follow-up outpatient provider visits), and unmet personal assistance needs (e.g., inability to obtain and install durable medical equipment, lack of health advocacy).
In the case of social isolation, hospitalization may be the only opportunity to identify older adults at risk and offer an interventional plan of mitigation. Further investigations are needed to develop in-hospital screening tools for social isolation and frameworks for post-hospital care. These interventions will be important not only after an ICU stay, but may be more crucial for hospitalization(s) preceding the development of critical illness in the hope of improving outcomes after a future ICU stay.
REFERENCES
- Cudjoe TKM, Roth DL, Szanton SL, et al. The epidemiology of social isolation: National Health and Aging Trend Study. J Gerontol B Psychol Soc Sci 2020;75:107-113.
- Shankar A, McMunn A, Demakakos P, et al. Social isolation and loneliness: Prospective associations with functional status in older adults. Health Psychol 2017;36:179-187.
- Davies K, Maharani A, Chandola T, et al. The longitudinal relationship between loneliness, social isolation, and frailty in older adults in England: A prospective analysis. Lancet Healthy Longev 2021;2:E70-E77.
- Ward M, May P, Normand C, et al. Mortality risk associated with combinations of loneliness and social isolation. Findings from The Irish Longitudinal Study on Ageing (TILDA). Age Ageing 2021;50:1329-1335.
- Haddad DN, Mart MF, Wang L, et al. Socioeconomic factors and intensive care unit-related cognitive impairment. Ann Surg 2020;272:596-602.
- Ferrante LF, Pisani MA, Murphy TE, et al. Functional trajectories among older persons before and after critical illness. JAMA Intern Med 2015;175:523-529.
- Prescott HC, Carmichael AG, Langa KM, et al. Paths into sepsis: Trajectories of presepsis healthcare use. Ann Am Thorac Soc 2019;16:116-123.
In this observational cohort study drawn from the National Health and Aging Trends Study, social isolation among older adults admitted to the intensive care unit was associated with greater disability burden and higher one-year mortality rates after critical illness.
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