Stature as a prognostic factor in cystic fibrosis survival

Abstract

Objective/design: This study provides a longitudinal analysis of the National Cystic Fibrosis Patient Registry to determine if height-for-age percentile would be a useful predictor of survival.

Subjects: All patients were selected from the national registry (n = 19,000) maintained by the Cystic Fibrosis Foundation's 115 accredited Cystic Fibrosis Care Centers in the United States. Inclusion in our analysis required that subjects were born between 1980 and 1989; had a minimum of 4 records each; the subject was alive at age 7; and the subject had a recorded height measurement at age 7 to 8 (n = 2,773).

Statistical analysis: The Cox proportional hazards model was used to compare height-for-age with survival. We recorded whether a subject was less than the 5th National Center for Health Statistics (NCHS) percentile at age 5 and then in a separate analysis at age 7. Cohort effect was coded as "1" if they were born before 1982 and "0" otherwise.

Results: Stature is a significant prognostic indicator of survival. The relative hazard associated with height below the 5th NCHS percentile for age was significant for both males and females. In males at age 5 the relative hazard was 2.9, [95% confidence interval (CI) 1.23, 6.91; P < .02] and at age 7 it was 6.3 (95% CI 2.1, 18.8; P < .001). The relative hazard in females at age 5 was 4.3 (95% CI 2.4, 7.3; P < .0001) and at age 7 was 5.8 (95% CI 2.5, 13.1; P < .0001).

Application: These highly significant relative hazard values strongly suggest that shorter patients are much more likely to die before taller patients. The dietetic professional should consider using height-for-age as an effective screening tool to identify patients at risk. Based on these data, short stature should not be considered benign to patients with cystic fibrosis. The CF team, clinicians, family, and patients need work together to maximize linear growth through medical and nutritional intervention.