Gunilla Wastensson, Eva M Andersson and Rita Bast-Pettersen
Objective: The CATSYS Tremor Pen has been used in several studies for measurement of tremor among workers with occupational exposure to neurotoxins like mercury and manganese. The main purpose of this study was to investigate whether recording time has an impact on the measured tremor characteristics. Other aims were to investigate whether there are interactions between recording time and age, and between recording time and (selfreported) nicotine use, respectively; to assess the test-retest repeatability of the instrument; to investigate a possible practice effect when performing the test repeatedly; and to evaluate agreement with another tremor test.
Methods: The participants (n=44) consisted of former shipyard workers (mean age 67 years, range 59–76 years). Postural hand tremor was evaluated using the CATSYS Tremor Pen. Five tremor recordings were made; the first lasted 16.4 s, the next three lasted 8.2 s each and the fifth lasted 65.6 s.
Results: There was a significant association between recording time and harmonic index; longer recording time produced higher harmonic index. There was no effect of nicotine use or age that was consistent over all recording times, and no practice effect was seen. The agreement with another tremor test was moderate to good, as was the test-retest reliability.
Conclusion: Some of the tremor characteristics are affected by length of recording time and hence care should be taken when comparing results across studies or with follow-up. The results indicate that the use of a recording time longer than 16.4 s seems to be of doubtful value.