Functional status after lung transplantation in older adults in the post-allocation score era

Abstract

This manuscript describes the functional status trajectory of older (age 65 or older) and younger (age 18-64) adults after lung transplantation (LT). After the implementation of the lung allocation score (LAS) in 2005, older adults became the fastest growing subgroup of recipients. Yet the impact of LT on physical function, a main determinant of quality of life in older adults, is unknown. We conducted a retrospective cohort study using United Network for Organ Sharing data on 4805 adults who received a LT during 2005-2009. We divided them into older (≥65; n = 774) and younger (18-64; n = 4031) cohorts. Functional status was measured by Karnofsky performance score (KPS). Mixed models estimated the impact of age group on the rate of functional decline starting at 1 year posttransplantation. We controlled for KPS at transplantation, gender, race, diagnosis, LAS and LT type. Age group was not associated with different rates of decline in KPS over time. On average, recipients who were older, received a single LT, or had a low KPS at transplantation had worse functional status posttransplantation when compared to their counterparts, but rarely reached disability at 48 months. Overall, LT had a positive and durable effect on physical function for both older and younger recipients.

Figure 1. Consort diagram for sample selection using data from the United Network for Organ Sharing registry

Abbreviations: Lung transplantation (LT), Karnofsky Performance Score (KPS), United Network for Organ Sharing (UNOS)

Figure 2. Boxplot Kamofsky Performance Score (mean ± standard deviation) overtime for Adult Lung Transplantation Recipients by level of Function at Transplantation

The levels of function represented are: 1) full assistance with self-care = KPS 10–40; 2) minimal assistance with self-care = KPS 50–70; 3) No assistance with self-care = 80–100. The groups did not reach ad KPS ≤ 60 at 48 months post-transplantation. The confidence intervals are wider for the group requiring full assistance with care at transplantation (KPS 10–40) and for all groups after 48 months. Abbreviations: Karnofsky Performance Score (KPS), lung transplantation (LT).

Figure 3. Boxplot of Karnofsky Performance Score (mean ± standard deviation) overtime for Younger (Age 18–64) and Older (Age ≥65) Adult Lung Transplantation Recipients

Younger and older Lung Transplantation recipients rarely reached a KPS ≤60 at 48 months post-transplantation. The confidence intervals for the older group widen over time, especially after 48 months.

Figure 4. Long-term Functional Trajectory of Younger (age 18–64) and Older (age ≥65) Lung Transplantation Recipients by level of Function at Transplantation

Functional status (y axis) was measured using Karnofsky Performance Score (KPS). The dotted line represents a clinically predictive cut off for higher risk for hospitalization, nursing home placement and death in older adults. Levels of functional status at transplantation (tKPS) are: Low = tKPS 10, intermediate = tKPS 60 and high = tKPS 100. This model used age group as main independent variable and time and tKPS as covariates.

Figure 5. Long-term Functional Status Trajectories for the Older (age 64–69) and the Oldest (age ≥70) Lung Transplantation Recipients by level of Function at Transplantation

Functional status (y axis) is measured by Karnofsky Performance Score (KPS). The dotted line represents a clinically predictive cut off for higher risk for hospitalization, nursing home placement and death in older adults. The levels of functional status at transplantation are: Low = tKPS 10, intermediate = tKPS 60 and high = tKPS 100. The model used age group as main independent variable and time and tKPS as covariates.

Figure 6. Predicted Survival over time for Younger (age 18–64) and Older (age ≥65) Lung Transplantation Recipients conditional on being alive at 11 months

These are the number of recipients alive at different months after lung transplantation for each age group.