Grouping of patients in medicine should be done keeping in mind the physiologic similarities and common risk factors for a particular age range. The inflection points for changes in survival have made this evident that following the standard or conventional cutoffs for age ranges inappropriately groups vulnerable populations of young adults (18–29 years) with older age patients in a broader “adult group.” The 22 years old is more akin to the 18 years old than the 40 years old physically, psychologically, and socially. They are likely to receive general adult treatment protocols which can put them at risk of poor posttransplant outcomes as they are not designed keeping their specific physiologic and social differences (pharmacokinetics, Human Leukocyte Antigen response, etc.) in mind. In younger patients, the body is growing and goes through rapid physiologic changes as well as responds to stressors differently. Literature has described the difference in physiology for adolescents leading to poor transplant outcomes, and the maturation of their physiology is gradual and is not complete at 18 years old.14 Most likely, the young adults who are often grouped with all adults have the similar physiology to older adolescents, which more than the course of young adulthood gradually transforms into adult physiology.
Critically ill patients like HTx patients bridged with a VAD require long-term medical care and follow-up and have to live a “vulnerable” life compared with the general healthy population because of a constant lifelong risk for deterioration of their medical condition. For these patients, psychosocial factors in addition to physiologic factors also play a key role in determining the long-term outcome.15 Medication compliance including transparent and engaging communication is an integral to positive outcomes after a HTx and adolescents are not great communicators at times and evidence clearly demonstrates issues with medication noncompliance.16 The decrease in survival around 15 years of age and then increase in survival around 30 years of age in the current study can perhaps also be explained due to the psychosocial factors affecting medication compliance, communication, and general self-care. Until around 15 years of age, parents/guardians are usually responsible to taking care of child’s health and medication compliance. Around 15 years is the age at which children start feeling more independent and are at risk for carelessness about themselves. This behavioral change continues into the young adulthood until they become psychologically mature, and by the age of around 30 years, there is a general shift toward a responsible approach to life and a move away from the care-free lifestyle. This “age 30 transition” (28–33 years) is a period when a person is likely to take important decisions regarding life partner, parenthood, family, work, and lifestyle.19 These behavioral changes can have impact on personal health and medication compliance, which in turn can impact posttransplant survival.
The study analyzed and compared pretransplant baseline characteristics in each age group to note differences and see what their impact was on the poor outcomes observed for patients age 15–29 years. Despite the age group of 8–14 years old only differing from our at-risk (15–29 years) cohort in a significantly higher frequency of several well-documented risk factors (more females, patients with a diagnosis of CHD, poor renal function, IV inotropic, and ventilator support), their survival was better than the 15–29 years old cohort. This clearly demonstrates that being in age group of 15–29 years is a strong risk factor for poor transplant outcomes, as was clearly demonstrated in the multivariable analysis.
Our study had certain limitations. As it is a retrospective study from a national database, there is always a possibility of inaccurate data collection. Another important limitation was that medication compliance could not be calculated as UNOS database has discontinued recording medication noncompliance events after 2006. Unfortunately, we do not have sufficient posttransplant information in the UNOS dataset which can give possible explanation of the worse outcomes in 15–29 years age patients.
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