Age of onset: can we rely on essential tremor patients to report this? Data from a prospective, longitudinal study.

BACKGROUND

Essential tremor (ET) is among the most prevalent neurological diseases. Age of onset, a key variable in neuroepidemiological and genetic research, is chiefly assessed by self-report rather than medical record review; the latter may be of little use. As a researcher, one wonders about the quality of this self-report. Is age of onset something which can be reproducibly self-reported by patients? There are few published data to aid researchers.

METHODS

Age of onset was self-reported at two time points (baseline and follow-up) in 86 ET cases in a longitudinal epidemiological study in New York.

RESULTS

The mean follow-up interval was 5.7 ± 2.5 (maximum = 14) years. Overall, agreement between the baseline and follow-up reports was high (ρ = 0.85, p < 0.001). Yet the difference (age of onset (baseline) - age of onset (follow-up)) ranged widely (from -47 to 32 years), and in one fifth of cases was ≥ 10 years. Greater agreement was associated with several clinical factors including age, medication use, embarrassment, depressive symptoms, cognitive test score and disease duration.

CONCLUSIONS

Differences in reported age of onset in ET may vary widely, and in up to one fifth of patients may be substantial. Investigators should approach these self-reports with caution.