TABLE 6.
Published Literature on the Prevalence of LP in Autopsy Series (Ordered by Reported Proportion With LP)
| Country (Author and Year) | n | Mean Age or Approximate Mean Age of Sample (Years) | Reported Proportion With LP* | Fully Excluded PD Cases?† | Excluded ET Cases? | Revised Estimate of Proportion With LP (After Correcting for ET)‡ | Revised Estimate of Proportion With LP (After Correcting for Both ET and PD)§ |
|---|---|---|---|---|---|---|---|
| Austria (Jellinger et al, 2012) | 100 | 81.2 | 5.0% | Uncertain¶ | No | 3.5% | 1.6% |
| USA (Knopman et al, 2003) | 39 | 85 | 12.8% | Uncertain¶ | No | 11.9% | 10.2% |
| Finland (Parkkinen et al, 2003) | 904 | 70–72 | 13.4% | No | No | 12.5% | 11.5% |
| Finland (Parkkinen et al, 2001) | 774 | 70–72 | 14.1% | No | No | 13.3% | 12.5% |
| USA (Dugger et al, 2014) | 119 | 88 | 14.3% | Uncertain¶ | Yes | Not applicable | 12.6% |
| Finland (Parkkinnen et al, 2008) | 1720 | 70–72 | 14.4% | No | No | 13.6% | 12.7% |
| USA (Frigerio et al, 2011) | 235 | 82 | 14.5% | Uncertain¶ | No | 13.7% | 12.0% |
| USA (Fujishiro et al, 2008) | 241 | 79 | 14.9% | Uncertain¶ | No | 14.2% | 12.5% |
| USA (White et al, 2009) | 443 | 80s? | 15.4% | No | No | 14.6% | 13.0% |
| Switzerland (Block et al, 2006) | 98 | 80.7 | 17.3% | Uncertain¶ | No | 16.8% | 15.2% |
| Japan (Saito et al, 2004) | 1,241 | 80.6 | 20.5% | No | No | 20.1% | 18.6% |
| Japan (Wakisaka 2003) | 102 | 80.2 | 22.5% | No | No | 22.4% | 20.9% |
| USA (Markesbery et al, 2009) | 139 | 83.5 | 23.7% | No | No | 23.6% | 22.1% |
| England (Zaccai et al, 2008) | 208 | 80s | 36.5% | No | No | 37.4% | 36.2% |
Ability to exclude a diagnosis of ET would have meant that the study had introduced the term “essential tremor” in the Materials and Methods section, a description of the method of evaluating ET was documented (including the specific items introduced into the neurological examination), details about the rating of tremor on neurological examination and the expertise of the rater were provided, and the specific diagnostic criteria used to assign diagnoses of ET were provided.
†The study did not provide detailed explanations about the methods for excluding individuals with PD. Also see footnote¶ below.
‡In studies that did not systematically exclude individuals with ET from their “normal population,” the estimate of the percentage of normal individuals with LP is likely inflated. To adjust for this, we first examined published data on the prevalence (%) of ET in individuals with the mean age of the sample in the study. Based on the data presented in this article (i.e. that 25.1% of ET cases have LP), we then assumed that 25% of these would have had LP. We then removed from the denominator the expected number of individuals presumed to have had ET and we removed from the numerator 25% of that number.
§In studies that did not systematically exclude individuals with PD from their “normal population,” the estimate of the percentage of normal individuals with LP is likely inflated. To adjust for this, we first examined published data on the prevalence (%) of PD in individuals with the mean age of the sample in the study. We then removed from both the numerator and the denominator the expected number of individuals presumed to have had PD.
Uncertain for one of the following reasons: (1) not clear how many individuals were examined by a neurologist or by a movement disorders neurologist, (2) not clear what type of neurological examination was performed and in how much detail parkinsonian features were assessed, and (3) not clear how many individuals were followed with neurological examinations to a point close in time to death.