Fat-free mass depletion in cystic fibrosis: Associated with lung disease severity but poorly detected by body mass index

Body composition and pulmonary function in cystic fibrosis

BACKGROUND

Lower body mass index (BMI) is associated with worse pulmonary function in cystic fibrosis (CF).

HYPOTHESIS

lean body mass (LBM) is more strongly associated with pulmonary function than BMI is.

METHODS

Anthropometrics, body composition by dual x-ray absorptiometry, and pulmonary function were determined in pancreatic insufficient CF (PI-CF) youth. Sex and age-adjusted Z-scores (BMI-Z, LBMI-Z, FMI-Z) were generated for CF and controls. (1) Associations of BMI-Z with LBMI-Z and FMI-Z and (2) age-adjusted associations of BMI-Z, LBMI-Z, and FMI-Z with FEV1%-predicted were tested.

RESULTS

Two hundred eight PI-CF subjects had lower BMI-Z, LBMI-Z, and FMI-Z compared to 390 controls. BMI-Z was associated with lower LBMI-Z (p < 0.0001) in PI-CF. In females, LBMI-Z and BMI-Z were positively associated with FEV1%-predicted; this relationship did not persist for FMI-Z after adjustment for LBMI-Z. In males, only LBMI-Z and BMI-Z were associated with FEV1%-predicted.

CONCLUSION

In PI-CF youth, deficits in LBM were apparent. At lower BMI percentiles, BMI may not accurately depict LBM in PI-CF. In under-nourished PI-CF youth, this preservation of FM in preference to LBM is relevant since LBMI-Z, but not FMI-Z, is positively associated with FEV1%-predicted. Lean body mass index is more strongly associated with lung function compared to BMI, especially in the under-nourished child and adolescent with PI-CF.

Changes in body composition after lung transplantation in children

BACKGROUND

The evaluation of nutritional status, including body composition measurements, in pediatric patients before and after lung transplant (LTx) can aid in adapting nutrition support and physical rehabilitation programs to meet individual patient needs. The purpose of this retrospective study was to determine the changes in weight, lean body mass (LBM), and body fat (BF) before and after LTx and their association with lung function in pediatric patients.

METHODS

Included were 41 LTx patients, aged 3 months to 20.7 years, who had at least 2 body composition measurements determined by dual-energy X-ray absorptiometry (GE Lunar Prodigy, Waukesha, WI) in the first 2 years after LTx were measured pre-LTX and at 12 or 24 months post-LTX, for weight, LBM, and BF.

RESULTS

Pre-LTx, 29% of patients had moderate and 12% had severe chronic malnutrition (growth stunting). This compares with 21% of patients being moderately LBM-depleted and 23% being BF-depleted. The weight change at 12 and 24 months was +9.3% (interquartile range, 5.6%-23%) and +4.7% (0.9%-11.6%), respectively; whereas the LBM change at 12 and 24 months was +15.2% (6.8%-17.1%) and +4.2% (-0.6% to 7.7%), respectively. LBM percentiles correlated with pulmonary function tests ( % predicted forced vital capacity [ρ = 0.36, p = 0.001] and forced expiratory volume in 1 second [ρ = 0.265, p = 0.015).

CONCLUSIONS

Maximum weight and LBM gain occur at 12 months after LTx, with smaller gains noted at 24 months. Clinicians must look beyond height and weight and evaluate LBM and fat mass in pediatric patients after LTx.

Loss of fat-free mass over four years in adult cystic fibrosis is associated with high serum interleukin-6 levels but not tumour necrosis factor-alpha

BACKGROUND & AIMS

Malnutrition is associated with poorer outcome in cystic fibrosis (CF). This follow-up study aimed to document nutritional status changes, including fat-free mass (FFM), in adults with CF; and to identify predictors of FFM loss.

METHODS

Fifty-eight non-transplanted CF adults (mean ± SD forced expiratory volume in one second (FEV1) 63.7 ± 21.4%predicted; mean ± SD age 30.3 ± 7.7years at baseline) were studied at baseline and 3.6 ± 0.4 years later. Body composition was measured using dual-energy X-ray absorptiometry. At follow-up, blood was analysed for interleukin-6 and tumour necrosis factor-α (TNF-α) on three occasions over six months and averaged for each participant. Associations with annual percentage change in FFM (ann%ΔFFM), including cytokines, CF genotype and annual change in FEV1%predicted (annΔFEV1%), were determined.

RESULTS

Mean FFM was 49.5 ± 8.8 kg at baseline and 49.6 ± 8.9 kg at follow-up (p = 0.66). Ann%ΔFFM ranged from -2.0 to +3.6%. FEV1%predicted declined by 1.2 ± 2.4% per year. Forty percent of participants had elevated average interleukin-6 levels. Ann%ΔFFM was negatively correlated with interleukin-6 levels (rho -0.34, p = 0.008), but not TNF-α or annΔFEV1%. F508DEL homozygote or heterozygote participants had greater FFM loss than those carrying no F508DEL allele (p = 0.01).

CONCLUSION

Higher serum interleukin-6 and presence of the F508DEL mutation, but not TNF-α, were associated with FFM loss in adults with CF.

BPI-ANCA and long-term prognosis among 46 adult CF patients: a prospective 10-year follow-up study

Introduction. Anti-neutrophil cytoplasmic antibodies specific for bactericidal/permeability-increasing protein (BPI-ANCA) are frequent in CF patients and mainly develop in response to infection with Pseudomonas aeruginosa. It is not known to what extent BPI-ANCA correlates to prognosis. Objectives. To evaluate the prognostic value of IgA-BPI-ANCA, measured at the beginning of the study, for transplantation-free survival. Methods. A cohort of 46 adult, nontransplanted CF patients was generated, 1995–1998, and characterized using Leeds criteria, lung function, and IgA-BPI-ANCA levels measured by ELISA. The cohort was followed until December 2009, using the combined endpoint of death or lung transplantation. Results. Lung function and IgA-BPI-ANCA, but not Leeds criteria, were significantly associated with adverse outcome. No patient with normal lung function at baseline reached endpoint. Within 10 years 8/11 with high BPI-ANCA reached an endpoint compared to 3/17 ANCA-negative patients. A similar result was seen within the Leeds I group where 7 out of 9 BPI-ANCA-positive patients reached endpoint, compared to none of the 5 patients without BPI-ANCA. Conclusions. IgA-BPI-ANCA is associated with adverse outcome among Pseudomonas aeruginosa infected CF patients, suggesting that BPI-ANCA is a biomarker of an unfavourable host-pathogen interaction.

Measures of body habitus are associated with lung function in adults with cystic fibrosis: a population-based study

BACKGROUND

Body habitus differences may explain some of the variation in lung function between individuals with cystic fibrosis (CF). We tested the hypothesis that measures of lean muscle mass and obesity are independently associated with lung function in CF.

METHODS

Cross-sectional study design using UK CF registry data from 2096 clinically stable adults.

RESULTS

Serum creatinine and BMI were positively and independently associated with FEV1 and FVC. One standard deviation increment in serum creatinine was associated with an FEV1 increase of 171ml (95% confidence intervals CI: +116 to +227ml) in males and 90ml (95% CI: +46 to +133ml) in females. Compared to the reference group of 20-24.9kg/m(2), those with a BMI<20kg/m(2) had lower FEV1 with values of -642ml (95%CI: -784 to -500ml) for males and -468ml (95%CI: -564 to -372ml) for females.

CONCLUSIONS

Prospective studies and controlled trials are required to ascertain if these associations have therapeutic potential in modifying disease progression.

A pre-post retrospective study of patients with cystic fibrosis and gastrostomy tubes

OBJECTIVES

The aim of the study was to assess the efficacy of gastrostomy tube (GT) placement on improving nutritional status and pulmonary function in patients with cystic fibrosis (CF).

PATIENTS AND METHODS

Data were collected from the Minnesota Cystic Fibrosis Database. Subjects with at least 5 percent-predicted forced expiratory volume in 1 second (ppFEV1) and 1 BMI percentile (pBMI) measurements before and after GT placement were included. Median pBMI values were compared 2 years before and 1, 2, and 4 years after GT placement using a signed rank test. Longitudinal mixed model analysis was used to assess the effect of GT placement on ppFEV1. To assess the effect of ppFEV1 at GT placement on efficacy, the estimated ppFEV1 change was regressed against the ppFEV1 level at placement.

RESULTS

Forty-six subjects with CF who met entry criteria were identified. Mean estimated step changes in ppFEV1 at placement for men, women, boys, and girls were 2.16% (P = 0.52), 0.43% (P = 0.92), 0.99% (P = 0.65), and -0.91% (P = 0.74), respectively. Mean estimated slope changes of ppFEV1 after GT placement were 5.01% (P = 0.02), 4.48% (P = 0.07), 1.49% (P = 0.23), and 4.02% (P = 0.01) per year for men, women, boys, and girls, respectively. Median change in pBMI in the second year after GT placement was 13.3% (P ≤ 0.0001). Estimated coefficients for the effect of ppFEV1 level at placement on the ppFEV1 step and slope change were -0.041 (P = 0.28) and -0.005 (P = 0.84), respectively.

CONCLUSIONS

GT placement in patients with CF results in significant improvement in both pBMI and ppFEV1, except in women. The change in lung function after GT placement is not dependent on the level of lung function at placement.

Poor physical function in elderly women in low-level aged care is related to muscle strength rather than to measures of sarcopenia

Purpose:

To determine the prevalence of sarcopenia and investigate relationships among body composition, muscle strength, and physical function in elderly women in low-level aged care.

Subjects and methods:

Sixty-three ambulatory women (mean age 86 years) participated in this cross-sectional study where body composition was determined by dual energy X-ray absorptiometry (DXA); ankle, knee, and hip strength by the Nicholas Manual Muscle Tester; and physical function by ‘timed up and go’ (TUG) and walking speed (WS) over 6 meters. Body composition data from a female reference group (n = 62, mean age 29 years) provided cut-off values for defining sarcopenia.

Results:

Elderly women had higher body mass index (P < 0.001), lower lean mass (P < 0.001), and higher fat mass (P < 0.01) than the young reference group. Only a small proportion (3.2%) had absolute sarcopenia (defined by appendicular skeletal muscle mass/height squared) whereas 37% had relative sarcopenia class II (defined by percentage skeletal muscle mass). Scores for TUG and WS indicated relatively poor physical function, yet these measures were not associated with muscle mass or indices of sarcopenia. In multivariate analysis, only hip abductor strength predicted both TUG and WS (both P = 0.01).

Conclusion:

Hip strength is a more important indicator of physical functioning than lean mass. Measurement of hip strength may therefore be a useful screening tool to detect those at risk of functional decline and requirement for additional care. Further longitudinal studies with a range of other strength measures are warranted.

Body composition assessed by the 4-component model and association with lung function in 6-12-y-old children with cystic fibrosis

BACKGROUND

Malnutrition is an indicator of a poor prognosis in patients with cystic fibrosis (CF). Previous body-composition (BC) studies in children with CF used 2-component models (2CMs) to assess fat mass (FM) and fat-free mass (FFM), but to our knowledge no study has used the gold-standard 4-component model (4CM), which allows for a more accurate evaluation of the nature of both elements.

OBJECTIVE

We measured BC by using the 4CM in 6-12-y-old children with CF to 1) compare findings with those of healthy, matched control children and reference data; 2) relate BC to lung spirometry [forced expired volume in 1 s (FEV₁)]; and 3) compare findings with those from more commonly used 2CM techniques.

DESIGN

One hundred clinically stable children with CF (57% girls) aged 6-12 y were measured by using the 4CM. Children with CF underwent spirometry (FEV₁).

RESULTS

Girls with CF had significantly less FM than did healthy girls, even after adjustment for height and pubertal status; boys with CF had higher body mass index SD scores than did healthy boys. FM in girls was positively associated with the FEV₁ percentage predicted. The 2CM FM was significantly different from the 4CM FM, with differences dependent on sex and condition, although most techniques identified a relation between FM and FEV₁ in girls.

CONCLUSIONS

Although shorter than healthy children, boys with CF were heavier and had a BC within the normal range; however, girls with CF had lower FM than did healthy girls, and this was associated with poorer lung function. Given the worse prognosis in girls, this finding merits more attention. The reliability of 2CM techniques varied with sex and health status.