title: Circulating surfactant protein D is associated to mortality in elderly women: a twin study.
abstract: BACKGROUND
  Surfactant protein D (SP-D) is produced in the lungs and additional mucosal surfaces. Systemic SP-D levels are previously associated to aging-related- and lifestyle-related disorders and predicts mortality in cardiovascular and lung diseases. However, the association between higher serum SP-D levels and mortality in the general population is unknown. We hypothesized that increased systemic levels of SP-D may be used as prognostic factor for assessing the mortality in the elderly.
  
  
  RESULTS
  SP-D serum levels were measured in 689 elderly subjects and mortality ratios were investigated after a 13-year follow-up period. Survival analysis showed that increasing quartiles of serum SP-D levels were associated to mortality in 70+ year old women (hazard ratio [HR], 1.29; 95% confidence interval [CI], 0.93-1.78; p = 0.032) adjusted for age, smoking and BMI. Women with SP-D levels above 2100 ng/ml had significantly increased mortality when compared to elderly women with SP-D levels equal to or below 2100 ng/ml (HR, 1.45; 95% CI, 1.12-1.88; p = 0.005). The likelihood that the female twin with the highest SP-D level died first increased with increasing SP-D levels (p = 0.031) - that is, the bigger intra-pair difference in SP-D level, the higher the probability that the twin with the highest measure died first (odds ratio [OR], 1.66; p = 0.047).
  
  
  CONCLUSIONS
  The study demonstrates that higher circulating SP-D levels are associated with increased mortality rate in elderly women in this population-based cohort study. SP-D may serve as a biomarker to track the cardio-pulmonary health status in elderly women.
authors.affiliation: Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, J.B. Winsløws Vej 25, 5000 Odense, Denmark. hwulf@health.sdu.dk
authors.forename: Helle
authors.initials: H
authors.lastname: Wulf-Johansson
authors.forename: Mikael
authors.initials: M
authors.lastname: Thinggaard
authors.forename: Qihua
authors.initials: Q
authors.lastname: Tan
authors.forename: Sofie Lock
authors.initials: SL
authors.lastname: Johansson
authors.forename: Anders
authors.initials: A
authors.lastname: Schlosser
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.forename: Uffe
authors.initials: U
authors.lastname: Holmskov
authors.forename: Grith Lykke
authors.initials: GL
authors.lastname: Sorensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006304:Health Status; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D009026:Mortality; D011336:Probability; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*; D012307:Risk Factors; D012907:Smoking / Q000401:mortality; D016019:Survival Analysis
chemical_list: D015415:Biomarkers; D037663:Pulmonary Surfactant-Associated Protein D