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.