Post-ICU Syndrome and Social Determinants of Healths

In recent decades, advances in intensive care have substantially reduced mortality, with survival rates now ranging from 70 to 80% among critically ill patients. However, a considerable number of these survivors experience persistent sequelae after discharge from the intensive care unit (ICU), affecting their functionality, well-being, and ability to resume their everyday life. This set of sequelae has been conceptualized as Post-Intensive Care Syndrome (PICS), defined as the onset or worsening of physical, cognitive, and/or mental health impairments that develop after ICU hospitalization and persist beyond hospital discharge. PICS is a complex, multifactorial condition that can last for months or even years, significantly impacting the quality of life of survivors and their families. PICS encompasses a wide range of clinical manifestations. Physically, patients may experience muscle weakness, joint stiffness, decreased mobility, persistent fatigue, and difficulty performing activities of daily living. Cognitively, memory impairment, difficulty concentrating, deterioration of executive functions, and reduced attention span have been reported. Some patients also develop ICU-associated delirium, characterized by confusion, disorientation, and mental status changes. Symptoms of anxiety, depression, post-traumatic stress disorder (PTSD), and sleep disturbances are commonly reported psychological symptoms. These sequelae can reduce overall functional capacity, make it harder to return to work, and lead to loss of independence and impaired social participation, directly affecting the quality of life of patients and their caregivers. Prospective studies have shown that the consequences of PICS extend beyond the clinical setting, affecting occupational, social, and economic dimensions. In a UK cohort, one-third of survivors lost their jobs or retired within six months of discharge, and this proportion remained high at 12 months. In addition, a significant proportion required assistance with self-care, usually provided by family members, which negatively affected caregivers' employment and income. Persistent pain and fatigue were associated with a lower probability of returning to work.

Although PICS is highly prevalent, estimates vary considerably by population, definitions used, and timing of assessment after ICU discharge. Nevertheless, available evidence suggests that between 50% and 70% of intensive care survivors present one or more symptoms consistent with PICS; approximately six out of ten patients continue to experience at least one sequela a year after discharge. Physical impairments affect between 30% and 80% of patients, while cognitive impairment has been reported in ranges from 25% to 75%. In terms of mental health, the prevalence of anxiety and depression varies between 20% and 50%, and PTSD symptoms affect up to 20-30% of survivors. In addition, 30% to 60% have limitations in performing activities of daily living and reduced functional capacity, highlighting the magnitude of PICS's impact on long-term recovery.

Several risk factors for developing PICS have been identified, including advanced age, female gender, the presence of previous comorbidities, and lower educational or socioeconomic status. More broadly, these risk factors point to the relevance of social determinants of health (SDH), defined as the conditions in which people are born, grow, live, work, and age, as well as the social, economic, and political systems that shape these conditions, which are closely linked to health inequalities. Within this framework, perceived social position, an individual's subjective standing relative to others in society, distinct from objective indicators such as income or education, has emerged as a key determinant: survivors in lower social positions tend to present worse outcomes than those in higher positions. This is explained because social position translates into psychosocial factors such as social support, loneliness, and chronic stress, which are associated with the worst health outcomes.

Consistent with this perspective, research findings suggest that psychological and social factors play a central role in the development and persistence of PICS. The ICU experience can be traumatic, and post-discharge stressors-such as loss of independence, financial difficulties, and caregiving overload-can perpetuate symptoms. The negative impact on the health outcomes of survivors may be intensified due to the psychosocial conditions associated with the SDH, already present before hospitalization in the ICU; anxiety, depression, or PTSD during hospitalization, as well as a history of mental illness, increases the risk of persistent psychological sequelae.

In summary, despite the growing body of research on post-intensive care syndrome (PICS), it remains defined as a set of symptoms, despite the heterogeneity of the disorders patients present with. This approach limits our understanding of the condition and the design of interventions, as PICS encompasses multiple combinations of symptoms and trajectories of evolution. Identifying patient groups with different symptom profiles, along with associated factors and their evolution over time, can provide researchers and clinicians with the input needed to advance our understanding. Recognizing the influence of psychosocial factors described in the SDH model on post-ICU outcomes represents a promising avenue to advance this knowledge, building on available evidence, although mostly descriptive, that psychosocial factors contribute to PICS outcomes. Understanding how social determinants relate to different symptom patterns and trajectories would help identify intervention points to reduce the impact of social conditions on recovery. Consequently, this study seeks to deepen understanding of PICS, provide evidence for intervention design, and contribute to improving long-term outcomes and quality of life for ICU survivors, while also reinforcing efforts to optimize post-ICU care and attention to the sequelae of critical illness.

Chile is a particularly relevant setting for studying SDH and PICS, as marked disparities in health outcomes between social groups persist despite reforms aimed at reducing inequalities. Fragmentation of the healthcare system between the public and private sectors, together with high levels of socioeconomic inequality, could significantly influence recovery after ICU hospitalization. Inequalities translate into psychosocial factors, such as chronic stress and social support, that reflect individuals' social position within society.

This study examines the role of social determinants of health in post-ICU syndrome (PICS) symptoms, symptom profiles, and health outcomes among critically ill survivors. It also aims to (1) determine the prevalence of overall PICS, physical, cognitive, and mental health symptoms at all four data collection times, and associated risk factors; and (2) identify latent profiles of PICS symptoms and whether psychosocial determinants are associated with membership in these profiles.

To address the study aim, it will conduct a multicenter, prospective observational cohort study of 400 survivors, followed up to 12 months post-discharge from the ICU. It will recruit eligible patients from five hospitals in Chile.

It will evaluate physical, cognitive, and mental health impairment. It will also evaluate quality of life related to health, frailty, fatigue, chronic pain, and sleep impairment. Social Determinants of Health will be evaluated using different measures: social position, household socioeconomic status, chronic stress, perceived stress, social support, loneliness, and sociodemographic and previous health conditions.

It is expected to recruit 400 patients over the 4-year study period.