Table 1. Main Results Regarding Essential Tremor in NEDICES Study.
| Results | Comments | |
| Prevalence | Overall: 4.8% (95% CI = 4.2–5.4). | 34% of the ET cases had an affected relative and 79.7% were detected through the NEDICES study and had not been diagnosed by a physician prior to the NEDICES study assessment. |
| Men: 4.6% (95% CI = 3.7–5.4). | ||
| Women: 5.0% (95% CI = 4.2–5.8). | ||
| Incidence | 616 per 100,000 person-years (95% CI = 447–784) | 77% of incident cases were detected through the NEDICES study and had not been diagnosed by a physician prior to the NEDICES study assessment. |
| Mortality | Unadjusted RR = 1.59, 95% CI = 1.11–2.27, p = 0.01). | ET may be a disease not only of increased morbidity but of increased mortality as well. |
| Adjusted RR = 1.45, (95% CI = 1.01–2.08, p = 0.04). | ||
| Frailty | A 20-item frailty score, which assessed comorbid conditions, number of medications, and functional activity was higher in ET cases than in controls (8.6±5.2 vs. 6.8±4.6, p<0.001) | This study suggests that there may be an additional frailty syndrome in ET that is above and beyond what has been described previously. |
| Subjective well-being | The Philadelphia Geriatric Center Morale Scale score was lower in ET cases than controls (9.41±3.21 vs. 10.39±2.92, p<0.001) | Morale may be lower in ET cases than in matched controls. |
| Self-reported depressive symptoms | Prevalent ET cases were twice more likely than controls to report depression and three times more likely to be taking antidepressant medications. In prospective analyses, baseline self-reported depression and, perhaps, baseline use of antidepressant medication were associated with incident ET. | ET seems to be associated with depressive symptoms. |
| Cognitive functioning | ET cases performed less well than controls especially on tests of global cognitive performance and frontal executive function. Lower cognitive test scores were associated with more reported functional difficulty. During the 3-year follow-up period, baseline cognitive test scores declined at a rate that was seven-times faster in ET cases than controls | A frontosubcortical-type dysfunction occurs in some ET patients. Lower cognitive test scores in ET, rather than being clinically inconsequential, seem to have a clinical-functional correlate. |
| MCI | ET cases with tremor onset after age 65 years were 57% more likely to have mild cognitive impairment than controls (OR = 1.57, 95% CI = 1.03–2.38, p = 0.03). | Elderly-onset ET may be associated with MCI |
| Prevalent dementia | ET cases with tremor onset after age 65 were 70% more likely to be demented than were controls (OR = 1.70, 95% CI = 1.04–2.76, p = 0.03). | Elderly-onset ET may be associated with dementia |
| Incident dementia | ET cases with tremor onset after age 65 years were twice as likely to develop incident dementia than were controls (RR = 1.98, 95% CI = 1.14 -3.45, p = 0.01). | Elderly-onset ET may be associated with incident dementia |
| incident Parkinson's disease | ET cases were four times more likely than controls to develop incident PD during prospective follow-up. | The link between ET and incident PD has for the first time been formally quantified |
| Hearing impairment | In an adjusted logistic regression analysis participants who reported hearing impairment were 30% more likely to suffer from ET than were controls (OR = 1.3; 95% CI = 1.01–1.7, p = 0.04). | ET may be associated with hearing impairment. |
| Smoking | Smokers were nearly half as likely to have ET as were never smokers (adjusted OR = 0.58, p = 0.004). In addition, baseline heavy cigarette smoking was also associated with a lower risk of incident ET (adjusted RR = 0.29, p = 0.03) | Smoking may be associated with decreased the risk of developing ET |
| Ethanol | In an adjusted Cox model, the highest baseline drink-year quartile doubled the risk of incident ET (RR = 2.29, p = 0.018) | Higher levels of chronic ethanol consumption may be associated with increased the risk of developing ET |
Abbreviations: CI, confidence interval; ET, essential tremor; MCI, mild cognitive impairment; NEDICES, Neurological Disorders of Central Spain; OR, odds ratio; PD, Parkinson's disease; RR, relative risk.