How Hospitalization May Affect You.

Post-Hospital Syndrome — An Acquired, Transient Condition of Generalized Risk

Harlan M. Krumholz, M.D.
N Engl J Med 2013; 368:100-102January 10, 2013DOI: 10.1056/NEJMp1212324
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To promote successful recovery after a hospitalization, health care professionals often focus on issues related to the acute illness that precipitated the hospitalization. Their disproportionate attention to the hospitalization's cause, however, may be misdirected. Patients who were recently hospitalized are not only recovering from their acute illness; they also experience a period of generalized risk for a range of adverse health events. Thus, their condition may be better characterized as a post-hospital syndrome, an acquired, transient period of vulnerability. This theory would suggest that the risks in the critical 30-day period after discharge might derive as much from the allostatic and physiological stress that patients experience in the hospital as they do from the lingering effects of the original acute illness. At the time of discharge, physiological systems are impaired, reserves are depleted, and the body cannot effectively defend against health threats.
Nearly one fifth of Medicare patients discharged from a hospital — approximately 2.6 million seniors — have an acute medical problem within the subsequent 30 days that necessitates another hospitalization. These recently discharged patients have heightened risks of myriad conditions, many of which appear to have little in common with the initial diagnosis. The causes of readmission, regardless of the original admitting diagnosis, commonly include heart failure, pneumonia, COPD, infection, gastrointestinal conditions, mental illness, metabolic derangements, and trauma (see graphProportions of Rehospitalizations for Causes Other Than the Condition at Initial Discharge.). The breadth of these readmission diagnoses has been shown in studies using administrative claims and those using chart reviews. Thus, this observation is not likely to be merely the result of variation in coding. 
How might the post-hospital syndrome emerge? Hospitalized patients are not only enduring an acute illness, which can markedly perturb physiological systems, but are experiencing substantial stress. During hospitalization, patients are commonly deprived of sleep, experience disruption of normal circadian rhythms, are nourished poorly, have pain and discomfort, confront a baffling array of mentally challenging situations, receive medications that can alter cognition and physical function, and become deconditioned by bed rest or inactivity. Each of these perturbations can adversely affect health and contribute to substantial impairments during the early recovery period, an inability to fend off disease, and susceptibility to mental error.
Researchers have documented the prevalence and risk of these stressors. For example, hospitalized patients often experience disturbance of sleep, and studies have revealed polysomnographic abnormalities in hospitalized patients, including reductions in sleep time and stages R (rapid eye movement [REM]) and N3 (slow wave) and an increase in stage N1 (non-REM). This disruption can have debilitating behavioral and physiological effects: sleep deprivation adversely affects metabolism, cognitive performance, physical functioning and coordination, immune function, coagulation cascade, and cardiac risk. 
Nutritional issues during hospitalizations may cause problems, yet often receive limited attention. In one study, one fifth of hospitalized patients 65 years of age or older had an average nutrient intake of less than 50% of their calculated maintenance energy requirements. Malnutrition can affect every system in the body, resulting in impairment of wound healing, increased risk of infections and pressure ulcers, decreased respiratory and cardiac function, poorer outcomes of chronic lung diseases, increased risk of cardiovascular and gastrointestinal disorders, and poorer physical function.
On the cognitive front, hospitalized patients often meet a variety of health care professionals but have little time to learn their names or understand their roles. Schedules are often unpredictable, and in patients who are already under stress, information overload can be stressful and may even provoke confusion. Moreover, these stressors of hospitalization can cause delirium, which is associated with increased risk after discharge.
Pain and other discomforts, common among these patients, are often inadequately addressed. They can lead to sleep disorders, mood disturbances, and impaired cognitive functioning, and are known to influence immune and metabolic function. Moreover, medications to treat symptoms can negatively affect the early recovery period. Sedatives, especially benzodiazepines, are commonly prescribed and may become part of the discharge regimen. Undersedation can cause hypercatabolism, immunosuppression, hypercoagulability, and increased sympathetic activity. Oversedation can dull the senses and impair cognitive function and judgment and may also lead to post-traumatic stress disorder.
Finally, hospitalized patients commonly become deconditioned, so recently discharged patients often have impaired stamina, coordination, and strength, which place them at greater risk for accidents and falls.