An Investigation on Reliability and Reference Values among Healthy Controls in the UDDGait Study

Abstract: Dementia disorders are difficult to detect in the early stages of the disease. Therefore, it is of importance to develop new methods in early diagnostics. The Uppsala Dalarna Dementia and Gait Study has established a new method in diagnosing early stages of cognitive impairments. The new method Timed-Up-and-Go (TUG) dual-task, combines a gait test with a verbal task. This thesis analyses nine TUG variables for healthy controls and discusses differences between two age groups, subjects younger than 72 years and subjects 72 years or older. Reliability of the new method is the primary focus point and is assessed using Intraclass Correlation Coefficients (ICC) and Bland-Altman plots. Normative reference values for the continuous variables are estimated with the help of bootstrap confidence intervals for the 2.5 and 97.5 percentiles. The results show that the three variables measuring the time to complete the test have good to excellent reliability, while variables that measure combinations of gait and verbal tasks show poor to moderate reliability. The lower reliability for these variables could be explained by them being ratios or differences of other variables. Differences in reliability can be seen between the age groups, where younger subjects have lower reliability partly due to homogeneity. Results show that the reference values of healthy controls are different for the two age groups.