Heritability of biochemical kidney markers and relation to survival in the elderly--results from a Danish population-based twin study.
OBJECTIVE
We performed a twin study to assess the relative contribution of genetic and environmental factors to serum levels of urea, creatinine, urate and sodium in a population of 688 elderly twins (73-95 years). Furthermore, we tested the association between these biochemical values and mortality to examine the consequence of an abnormal biochemical kidney parameter in an aging population.


RESULTS
A third to a half of the variation in the biochemical kidney tests is due to genetic factors except for creatinine in males. Survival analysis show that all four parameters influence mortality and values below reference interval for urea and urate have a more pronounced impact on survival [hazard ratios (95% confidence interval): 2.32 (1.03-5.26) and 3.56 (1.46-8.69), respectively] than values above [1.20 (0.87-1.64) and 1.50 (1.11-2.02), respectively]. Increased creatinine (above 130 micromol/l) and decreased sodium (below 136 mmol/l) also have a significant impact on survival with hazard ratios on 1.83 (1.13-2.95) and 1.56 (1.22-1.99), respectively. Between 5% and 44% of the measured values are outside the established reference interval.


CONCLUSIONS
This study provides evidence for the importance of genetic factors in determining the biochemical kidney parameters in an aging population. Furthermore, our data shows that abnormal kidney parameters are common in older adults and results in a significant increase in mortality risk.
Department of Clinical Biochemistry, Odense University Hospital, Denmark. L.Bathum@ouh.fyns-amt.dk
Lise
L
Bathum
Corrado
C
Fagnani
Lene
L
Christiansen
Kaare
K
Christensen
D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking; D000465:Algorithms; D015415:Biomarkers / Q000032:analysis*; D001806:Blood Urea Nitrogen; D015992:Body Mass Index; D003404:Creatinine / Q000097:blood; D003718:Denmark / Q000453:epidemiology; D004777:Environment; D005260:Female; D006801:Humans; D007668:Kidney / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D012964:Sodium / Q000097:blood; D013534:Survival; D016019:Survival Analysis; D014427:Twins; D014527:Uric Acid / Q000097:blood
D015415:Biomarkers; D014527:Uric Acid; D012964:Sodium; D003404:Creatinine