Premature or early bilateral oophorectomy: a 2021 update

In this invited review, we discuss some unresolved and controversial issues concerning premature (<40 years) or early (40-45 years) bilateral oophorectomy. First, we clarify the terminology. Second, we summarize the long-term harmful consequences of bilateral oophorectomy. Third, we discuss the restrictive indications for bilateral oophorectomy in premenopausal women to prevent ovarian cancer that are justified by the current scientific evidence. Fourth, we explain the importance of estrogen replacement therapy when bilateral oophorectomy is performed. Hormone replacement therapy is indicated after bilateral oophorectomy until the age of expected natural menopause like in premature or early primary ovarian insufficiency. Fifth, we discuss the relationship between adverse childhood experiences, adverse adult experiences, mental health, gynecologic symptoms and bilateral oophorectomy. The acceptance and popularity of bilateral oophorectomy over several decades, and its persistence even in the absence of supporting scientific evidence, suggest that non-medical factors related to sex, gender, reproduction, cultural beliefs and socioeconomic structure are involved. We discuss some of these non-medical factors and the need for more research in this area.

Long-term health consequences of premature or early menopause and considerations for management

AIM

To review the current evidence concerning the long-term harmful effects of premature or early menopause, and to discuss some of the clinical implications.

MATERIAL AND METHODS

Narrative review of the literature.

RESULTS

Women undergoing premature or early menopause, either following bilateral salpingo-oophorectomy or because of primary ovarian insufficiency, experience the early loss of estrogen and other ovarian hormones. The long-term consequences of premature or early menopause include adverse effects on cognition, mood, cardiovascular, bone, and sexual health, as well as an increased risk of early mortality. The use of hormone therapy has been shown to lessen some, although not all of these risks. Therefore, multiple medical societies recommend providing hormone therapy at least until the natural age of menopause. It is important to individualize hormone therapy for women with early estrogen deficiency, and higher dosages may be needed to approximate physiological concentrations found in premenopausal women. It is also important to address the psychological impact of early menopause and to review the options for fertility and the potential need for contraception, if the ovaries are intact.

CONCLUSIONS

Women who undergo premature or early menopause should receive individualized hormone therapy and counseling.

Premorbid personality characteristics in Alzheimer's disease: an exploratory case-control study

Linking data from a case-control study of Alzheimer's disease with data from a Minnesota Multiphasic Personality Inventory (MMPI) outpatient study, we identified 13 Alzheimer's disease cases and 16 controls for case-control comparison. The mean time between personality testing and onset of Alzheimer's disease (or corresponding age for controls) was 13 years in cases and 14 years in controls. Alzheimer's disease cases, but not the controls, had scores significantly greater than the normative reference on MMPI scales measuring Social Introversion (p = 0.05), and Pessimism (p = 0.01). When compared to controls, Alzheimer's disease cases had significantly greater scores on the Social Introversion scale (p = 0.03). Despite the small sample size and some design limitations of this exploratory study, our findings may suggest that subjects who score higher on these personality scales have a greater risk of Alzheimer's disease.

The incidence of MCI differs by subtype and is higher in men: the Mayo Clinic Study of Aging

OBJECTIVE

Although incidence rates for mild cognitive impairment (MCI) have been reported, few studies were specifically designed to measure the incidence of MCI and its subtypes using published criteria. We estimated the incidence of amnestic MCI (aMCI) and nonamnestic MCI (naMCI) in men and women separately.

METHODS

A population-based prospective cohort of Olmsted County, MN, residents ages 70-89 years on October 1, 2004, underwent baseline and 15-month interval evaluations that included the Clinical Dementia Rating scale, a neurologic evaluation, and neuropsychological testing. A panel of examiners blinded to previous diagnoses reviewed data at each serial evaluation to assess cognitive status according to published criteria.

RESULTS

Among 1,450 subjects who were cognitively normal at baseline, 296 developed MCI. The age- and sex-standardized incidence rate of MCI was 63.6 (per 1,000 person-years) overall, and was higher in men (72.4) than women (57.3) and for aMCI (37.7) than naMCI (14.7). The incidence rate of aMCI was higher for men (43.9) than women (33.3), and for subjects with ≤12 years of education (42.6) than higher education (32.5). The risk of naMCI was also higher for men (20.0) than women (10.9) and for subjects with ≤12 years of education (20.3) than higher education (10.2).

CONCLUSIONS

The incidence rates for MCI are substantial. Differences in incidence rates by clinical subtype and by sex suggest that risk factors for MCI should be investigated separately for aMCI and naMCI, and in men and women.

Prevalence of mild cognitive impairment is higher in men. The Mayo Clinic Study of Aging

OBJECTIVE

We investigated the prevalence of mild cognitive impairment (MCI) in Olmsted County, MN, using in-person evaluations and published criteria.

METHODS

We evaluated an age- and sex-stratified random sample of Olmsted County residents who were 70-89 years old on October 1, 2004, using the Clinical Dementia Rating Scale, a neurologic evaluation, and neuropsychological testing to assess 4 cognitive domains: memory, executive function, language, and visuospatial skills. Information for each participant was reviewed by an adjudication panel and a diagnosis of normal cognition, MCI, or dementia was made using published criteria.

RESULTS

Among 1,969 subjects without dementia, 329 subjects had MCI, with a prevalence of 16.0% (95% confidence interval [CI] 14.4-17.5) for any MCI, 11.1% (95% CI 9.8-12.3) for amnestic MCI, and 4.9% (95% CI 4.0-5.8) for nonamnestic MCI. The prevalence of MCI increased with age and was higher in men. The prevalence odds ratio (OR) in men was 1.54 (95% CI 1.21-1.96; adjusted for age, education, and nonparticipation). The prevalence was also higher in subjects who never married and in subjects with an APOE epsilon3epsilon4 or epsilon4epsilon4 genotype. MCI prevalence decreased with increasing number of years of education (p for linear trend <0.0001).

CONCLUSIONS

Our study suggests that approximately 16% of elderly subjects free of dementia are affected by MCI, and amnestic MCI is the most common type. The higher prevalence of MCI in men may suggest that women transition from normal cognition directly to dementia at a later age but more abruptly.

Novelty seeking and introversion do not predict the long-term risk of Parkinson disease

OBJECTIVE

It has been suggested that people who develop Parkinson disease (PD) may have a characteristic premorbid personality. We tested this hypothesis using a large historical cohort study with long follow-up.

METHODS

We conducted a historical cohort study in the region including the 120-mile radius centered in Rochester, MN. We recruited 7,216 subjects who completed the Minnesota Multiphasic Personality Inventory (MMPI) for research at the Mayo Clinic from 1962 through 1965 and we considered 5 MMPI scales to measure sensation seeking, hypomania, positive emotionality, social introversion, and constraint. A total of 6,822 subjects (94.5% of the baseline sample) were followed over 4 decades either actively (via interview and examination) or passively (via medical records).

RESULTS

During follow-up, 227 subjects developed parkinsonism (156 developed PD). The 3 MMPI scales that we selected to measure the extroverted personality construct (sensation seeking, hypomania, and positive emotionality) did not show the expected pattern of higher scores associated with reduced risk of PD. Similarly, the 2 MMPI scales that we selected to measure the introverted personality construct (social introversion and constraint) did not show the expected pattern of higher scores associated with increased risk of PD. However, higher scores for constraint were associated with an increased risk of all types of parkinsonism pooled together (hazard ratio 1.39; 95% CI 1.06-1.84; p = 0.02).

CONCLUSIONS

We suggest that personality traits related to introversion and extroversion do not predict the risk of PD.

Study on the validity of the Hodkinson Abbreviated Mental Test Score (AMTS) in detecting dementia of elderly subjects in appignano (Macerata province), Italy

The accuracy of the Hodkinson Abbreviated Mental Test Score (AMTS) as a screening instrument for dementia has been investigated in an Italian population. The AMTS was administered by nonmedical personnel to a random sample of 109 subjects over the age of 59; each subject was evaluated by a standardized dementia protocol (DSM-III criteria); and scores on the AMTS were compared to corresponding clinical diagnoses (standard for comparison). Five of the 109 subjects were found to be affected by dementia upon clinical investigation. Although a score of 6 showed the best combination of sensitivity (80%) and specificity (89%), only a score of 7 yielded 100% sensitivity (71% specificity). At all screening levels, specificity was higher for males vs. females, for younger vs. older, and for more educated vs. less educated subjects. The results suggest that brief cognitive tests may be successfully used in population screening for dementia, and that tests not requiring reading, writing or drawing, and not strictly dependent on the education level, are preferable; however, the instruments should be adapted and validated in the target population.

Medical records documentation of constipation preceding Parkinson disease: A case-control study

OBJECTIVE

Parkinson disease (PD) may affect the autonomic nervous system and may cause constipation; however, few studies have explored constipation preceding the motor onset of PD. We investigated constipation preceding PD using a case-control study design in a population-based sample.

METHODS

Using the medical records-linkage system of the Rochester Epidemiology Project, we identified 196 subjects who developed PD in Olmsted County, MN, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. We reviewed the complete medical records of cases and controls in the medical records-linkage system to ascertain the occurrence of constipation preceding the onset of PD (or index year).

RESULTS

Constipation preceding PD or the index year was more common in cases than in controls (odds ratio [OR] 2.48; 95% confidence interval [CI] 1.49 to 4.11; p = 0.0005). This association remained significant after adjusting for smoking and coffee consumption (ever vs never), and after excluding constipation possibly induced by drugs. In addition, the association remained significant in analyses restricted to constipation documented 20 or more years before the onset of motor symptoms of PD. Although the association was stronger in women than in men and in patients with PD with rest tremor compared with patients with PD without rest tremor, these differences were not significant.

CONCLUSIONS

Our findings suggest that constipation occurring as early as 20 or more years before the onset of motor symptoms is associated with an increased risk of Parkinson disease.

Anemia or low hemoglobin levels preceding Parkinson disease: a case-control study

OBJECTIVE

It has been suggested that anemia may be a risk factor for dementia, for restless legs syndrome, and for Parkinson disease (PD). Thus, we investigated the association of anemia with the subsequent risk of PD using a case-control study design.

METHODS

We used the medical records-linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, Minnesota, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. We reviewed the complete medical records of cases and controls in the system to detect anemia defined using the World Health Organization criteria.

RESULTS

Anemia was more common in the history of cases than of controls (odds ratio 2.00, 95% confidence interval 1.31-3.06, p = 0.001). The association remained significant after adjustment for cigarette smoking, exposure to pesticides, or hysterectomy (in women). The association was not significantly different between men and women, or between PD patients with or without rest tremor. Analyses stratified by time of onset of anemia showed a greater association for anemia that started 20 to 29 years before the onset of PD. Hemoglobin levels were slightly but consistently lower in cases than in controls across all ages.

CONCLUSIONS

Our results support an association between anemia experienced early in life and the later development of Parkinson disease. The interpretation of this association remains uncertain.

Long-term effects of bilateral oophorectomy on brain aging: unanswered questions from the Mayo Clinic Cohort Study of Oophorectomy and Aging

In the Mayo Clinic Cohort Study of Oophorectomy and Aging, women who had both ovaries removed before reaching natural menopause experienced a long-term increased risk of parkinsonism, cognitive impairment or dementia, and depressive and anxiety symptoms. Here, we discuss five possible mechanistic interpretations of the observed associations; first, the associations may be non-causal because they result from the confounding effect of genetic variants or of other risk factors; second, the associations may be mediated by an abrupt reduction in levels of circulating estrogen; third, the associations may be mediated by an abrupt reduction in levels of circulating progesterone or testosterone; fourth, the associations may be mediated by an increased release of gonadotropins by the pituitary gland; and fifth, genetic variants may modify the hormonal effects of bilateral oophorectomy through simple or more complex interactions. Results from other studies are cited as evidence for or against each possible mechanism. These putative causal mechanisms are probably intertwined, and their clarification is a research priority.

Alpha-synuclein, pesticides, and Parkinson disease: a case-control study

BACKGROUND

Aggregation and fibrillization of the alpha-synuclein protein (encoded by the SNCA gene) may represent key events in the pathogenesis of Parkinson disease (PD). Variability in the length of a dinucleotide repeat sequence (REP1) within the SNCA promoter confers susceptibility to sporadic PD. Pesticide exposures may also confer susceptibility to PD. Our objective was to test possible joint effects of SNCA REP1 genotypes and pesticide exposures on the risk of PD.

METHODS

This was a case-control study. Cases were recruited prospectively from the Department of Neurology of the Mayo Clinic, Rochester, MN, after June 1, 1996. The control subjects included unaffected siblings of cases and unrelated population control subjects. We assessed pesticide exposures by telephone interview and genotyped SNCA REP1. Odds ratios (ORs) and 95% CIs were determined using conditional logistic regression models.

RESULTS

There were 833 case-control pairs. We observed an increased risk of PD with increasing SNCA REP1 bp length (OR, 1.18 for each score unit; 95% CI, 1.02-1.37; p = 0.03). Pesticide exposures were associated with PD in younger subjects only (lowest quartile of age at study, <or=59.8 years; OR, 1.80; 95% CI, 1.12-2.87; p = 0.01 for all pesticides; OR, 2.46; 95% CI, 1.34-4.52; p = 0.004 for herbicides). In multivariate analyses, both SNCA REP1 score and pesticide exposures were significantly associated with PD in younger subjects, but there were no pairwise interactions.

CONCLUSIONS

Our findings suggest that SNCA REP1 genotype and herbicides have independent effects on risk of Parkinson disease, primarily in younger subjects.

Incident dementia in women is preceded by weight loss by at least a decade

BACKGROUND

Although several studies reported weight loss preceding the onset of dementia, other studies suggested that obesity in midlife or even later in life may be a risk factor for dementia.

METHODS

The authors used the records-linkage system of the Rochester Epidemiology Project to ascertain incident cases of dementia in Rochester, MN, for the 5-year period 1990 to 1994. The authors defined dementia using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). Each case was individually matched by age (+/-1 year) and sex to a person drawn randomly from the same population, and free from dementia in the index year (year of onset of dementia in the matched case). Weights were abstracted from the medical records in the system.

RESULTS

There were no differences in weight between cases and controls 21 to 30 years prior to the onset of dementia. However, women with dementia had lower weight than controls starting at 11 to 20 years prior to the index year, and the difference increased over time through the index year. We found a trend of increasing risk of dementia with decreasing weight in women both at the index year (test for linear trend; p < 0.001) and 9 to 10 years before the index year (test for linear trend; p = 0.001).

CONCLUSIONS

Even accounting for delays in diagnosis, weight loss precedes the diagnosis of dementia in women but not in men by several years. This loss may relate to predementia apathy, loss of initiative, and reduced olfactory function.

Increased risk of parkinsonism in women who underwent oophorectomy before menopause

OBJECTIVE

There is increasing laboratory evidence for a neuroprotective effect of estrogen on the nigrostriatal pathway; however, the epidemiologic evidence remains limited and conflicting. We studied the association of oophorectomy performed before the onset of menopause with the risk of subsequent parkinsonism.

METHODS

We included all women who underwent either unilateral or bilateral oophorectomy before the onset of menopause for a noncancer indication from 1950 through 1987 while residing in Olmsted County, MN. Each member of the oophorectomy cohort was matched by age to a referent woman in the same population who had not undergone oophorectomy. In total, we studied 1,252 women with unilateral oophorectomy, 1,075 women with bilateral oophorectomy, and 2,368 referent women. Women were followed through death or end of study using a combination of direct or proxy interviews, neurologic examinations, medical records in a records-linkage system, and death certificates.

RESULTS

Women who underwent either unilateral or bilateral oophorectomy before the onset of menopause had an increased risk of parkinsonism compared with referent women (HR 1.68; 95% CI 1.06 to 2.67; p = 0.03), and the risk increased with younger age at oophorectomy (test for linear trend; p = 0.01). The findings were similar regardless of the indication for the oophorectomy, and for unilateral or bilateral oophorectomy considered separately. The findings were also consistent for Parkinson disease alone, but did not reach significance.

CONCLUSIONS

Both unilateral and bilateral oophorectomy performed prior to menopause may be associated with an increased risk of parkinsonism and the effect may be age-dependent. However, our findings await independent replication.

Increased risk of cognitive impairment or dementia in women who underwent oophorectomy before menopause

OBJECTIVE

There is increasing laboratory evidence for a neuroprotective effect of estrogen; however, the clinical and epidemiologic evidence remains limited and conflicting. We studied the association of oophorectomy performed before the onset of menopause with the risk of subsequent cognitive impairment or dementia.

METHODS

We included all women who underwent unilateral or bilateral oophorectomy before the onset of menopause for a non-cancer indication while residing in Olmsted County, MN, from 1950 through 1987. Each member of the oophorectomy cohort was matched by age to a referent woman from the same population who had not undergone oophorectomy. In total, we studied 813 women with unilateral oophorectomy, 676 women with bilateral oophorectomy, and 1,472 referent women. Women were followed through death or end of study using either direct or proxy interviews.

RESULTS

Women who underwent either unilateral or bilateral oophorectomy before the onset of menopause had an increased risk of cognitive impairment or dementia compared to referent women (hazard ratio [HR] = 1.46; 95% CI 1.13 to 1.90; adjusted for education, type of interview, and history of depression). The risk increased with younger age at oophorectomy (test for linear trend; adjusted p < 0.0001). These associations were similar regardless of the indication for the oophorectomy, and for women who underwent unilateral or bilateral oophorectomy considered separately.

CONCLUSIONS

Both unilateral and bilateral oophorectomy preceding the onset of menopause are associated with an increased risk of cognitive impairment or dementia. The effect is age-dependent and suggests a critical age window for neuroprotection.

Immunologic diseases, anti-inflammatory drugs, and Parkinson disease: a case-control study

The authors studied the association of markers of inflammation with the later development of Parkinson disease (PD) using a case-control design (196 cases and 196 matched controls). The frequency of diseases of immediate-type hypersensitivity was significantly higher in cases than controls. In addition, cases used anti-inflammatory agents less frequently than controls (nonsignificant trend). The results may support the hypothesis that there is an inflammatory component in the pathogenesis of PD.

Education and occupations preceding Parkinson disease: a population-based case-control study

OBJECTIVE

To investigate the association of Parkinson disease (PD) with education and occupations using a case-control study design.

METHODS

The authors used the medical records-linkage system of the Rochester Epidemiology Project to identify all subjects who developed PD in Olmsted County, MN, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. The authors collected information about education and occupations using two independent sources of data: a review of the complete medical records in the system and a telephone interview. Occupations were coded using the 1980 Standard Occupational Classification.

RESULTS

Subjects with 9 or more years of education were at increased risk of PD (OR = 2.0; 95% CI = 1.1 to 3.6; p = 0.02), and there was a trend of increasing risk with increasing education (test for linear trend, p = 0.02; medical records data). Physicians were at significantly increased risk of PD using both sources of occupational data. By contrast, four occupational groups showed a significantly decreased risk of PD using one source of data: construction and extractive workers (e.g., miners, oil well drillers), production workers (e.g., machine operators, fabricators), metal workers, and engineers. These associations with increased or decreased risk did not change noticeably after adjustment for education.

CONCLUSION

Subjects with higher education and physicians have an increased risk of Parkinson disease (PD), while subjects with some occupations presumed to involve high physical activity have a decreased risk of PD.

Coronary artery bypass grafting is not a risk factor for dementia or Alzheimer disease

OBJECTIVE

To study coronary artery bypass grafting (CABG) as a risk factor for dementia and Alzheimer disease (AD) using a case-control design.

METHODS

The authors used the records-linkage system of the Rochester Epidemiology Project to ascertain incident cases of dementia in Rochester, MN, for the 5-year period 1990 to 1994. The authors defined dementia and AD using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). Each case was individually matched by age (+/-1 year) and sex to a person drawn randomly from the same population, and free of dementia in the index year (year of onset of dementia in the matched case).

RESULTS

Among 557 dementia cases, 24 (4.3%) had undergone a CABG prior to the onset of dementia with a median lag time of 5.5 years (range = 0.1 to 15.9). Among 557 controls, 28 subjects (5.0%) had undergone a CABG prior to the index year with a median lag time 3.9 years (range = 0.1 to 12.3); OR = 0.85 (95% CI = 0.49 to 1.49; p = 0.57) for dementia and OR = 0.78 (95% CI = 0.39 to 1.56; p = 0.48) for AD. The findings did not change after adjustment for education. The perioperative courses of cases and controls were comparable. Analyses including only the 481 cases of dementia with presumed neurodegenerative or cerebrovascular etiology were also negative.

CONCLUSIONS

This population-based case-control study suggests that coronary artery bypass grafting is not a major risk factor for dementia overall, or for Alzheimer disease.

The incidence of frontotemporal lobar degeneration in Rochester, Minnesota, 1990 through 1994

The records-linkage system of the Rochester Epidemiology Project was used to ascertain incident cases of frontotemporal lobar degeneration (FTLD) in Rochester, MN, from 1990 through 1994. Four cases of FTLD were identified (all women); two were confirmed neuropathologically. All were of the behavioral-dysexecutive type and had onset before age 70. The incidence rates (new cases per 100,000 person-years) were 2.2 for ages 40 to 49, 3.3 for ages 50 to 59, and 8.9 for ages 60 to 69. For comparison, the corresponding rates for Alzheimer disease were 0.0, 3.3, and 88.9.

A limited role for DJ1 in Parkinson disease susceptibility

An association study of four common polymorphisms in the DJ1 gene and Parkinson disease (PD) was conducted. PD probands were compared with their unaffected siblings matched by gender and closest age at study (416 vs 416) and with unrelated control subjects (691 vs 190). None of the four haplotype tagging single-nucleotide polymorphisms (SNPs) was associated with PD overall, but SNP1 (position 4,345 bp) and SNP3 (position 16,491 bp) were associated with PD in women (p = 0.03 and p = 0.002).

Validity of family history data on PD: evidence for a family information bias

OBJECTIVE

To study the validity of information provided by case and control subjects (or their proxies) about PD among their first-degree relatives.

METHODS

Secondary cases of PD were assessed both through a single informant (family history method) and through the study of each relative (family study method). The family study method was considered as the standard for comparison, and the sensitivity and specificity of the family history method were studied.

RESULTS

A total of 133 population-based case subjects and their 655 relatives were recruited, and 119 population-based control subjects and their 511 relatives. Sensitivity was 68% (95% CI = 47 to 85) for cases and 45% (95% CI = 17 to 77) for controls. Specificity was 99% (95% CI = 98 to 99) for cases and 100% (95% CI = 99 to 100) for controls. The odds ratio (OR) for family history of PD was 4.34 (95% CI = 1.63 to 11.58, p = 0.003) using the family history method and 1.86 (95% CI = 0.78 to 4.44, p = 0.16) using the family study method. The former significant OR more than doubled the latter not significant OR (relative bias = 133%). Bias was more pronounced for proxy interviews and for women informants, and when the relatives were siblings, were living, and were examined or had medical record documentation.

CONCLUSIONS

Case subjects with PD (or their proxies) are more aware of PD among their first-degree relatives than control subjects (or their proxies); however, they overreport PD in relatives who are not affected. This causes a substantial family information bias.

Head trauma preceding PD: a case-control study

OBJECTIVE

To investigate the association of PD with preceding head trauma using a case-control study design.

METHODS

The medical records-linkage system of the Rochester Epidemiology Project was used to identify 196 subjects who developed PD in Olmsted County, MN, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. The complete medical records of cases and controls in the system were reviewed to detect preceding episodes of head trauma.

RESULTS

The frequency of head trauma overall was significantly higher in cases than in controls (odds ratio [OR] = 4.3; 95% CI = 1.2 to 15.2). Compared with subjects who never experienced a trauma, subjects who experienced a mild head trauma with only amnesia had no increased risk; however, subjects who experienced a mild head trauma with loss of consciousness or a more severe trauma had an OR of 11.0 (95% CI = 1.4 to 85.2). Although not significant, head trauma resulting in hospitalization was more frequent in cases than in control subjects (OR = 8.0; 95% CI = 1.0 to 64.0). Whereas the OR was higher for men than women and for patients with later onset of PD than for patients with earlier onset, these differences were not significant.

CONCLUSIONS

These results suggest an association between head trauma and the later development of PD that varies with severity. Although the OR is high (4.3), the population attributable risk is only 5% because head trauma is a relatively rare event.

Case-Control study of the extended tau gene haplotype in Parkinson's disease

We investigated the association of Parkinson's disease with tau gene haplotypes. In a sample of 319 unrelated Parkinson's disease patients and 196 control subjects, we observed an increased risk of Parkinson's disease for persons with the H1/H1 genotype (odds ratio = 1.5; 95% confidence interval: 0.98-2.23); however, the finding was not statistically significant. The results remained similar after adjusting for the possible misclassification of progressive supranuclear palsy patients as Parkinson's disease, but became statistically significant after restricting the analysis to nondemented subjects.

Problems and issues with door-to-door, two-phase surveys: an illustration from central Spain

In 1994-1995, a screening and examination survey was conducted to ascertain the prevalence of dementia, Parkinson's disease and stroke in two urban communities and one rural community of central Spain. We use this survey to illustrate many nonclinical aspects of conducting two-phase prevalence surveys. Special emphasis is given to two common weaknesses in such surveys: screening nonparticipation and screening validation.

Door-to-door prevalence survey of epilepsy in three Sicilian municipalities

A door-to-door prevalence survey of epilepsy was conducted in 3 Sicilian municipalities, as of November 1, 1987. In phase 1, the screening by questionnaire of 24,496 eligible subjects (participation = 92%) identified 544 suspected to have epilepsy. In phase 2, neurological evaluation of the 544 subjects yielded 111 with epilepsy. Of the 111 subjects, 103 (93%) had been previously diagnosed, 68 (61%) were taking antiepileptic medication, and 81 (73%) had active epilepsy. Referring to the 81 subjects with active epilepsy, the seizure type was generalized in 60 (74%), partial in 19 (23%) and undetermined in 2 (3%). The prevalence of active epilepsy (per 1,000 population) was 3.3 overall, 3.5 for men and 3.2 for women. The age-specific patterns for active epilepsy differed by sex, with higher figures for men at younger ages (5-19 years) and older ages (50-99 years). The age-specific prevalence figures for active epilepsy were lower than those from previous Italian surveys.

Hysterectomy, menopause, and estrogen use preceding Parkinson's disease: an exploratory case-control study

We studied the association of Parkinson's disease (PD) with type of menopause (natural or surgical), age at menopause, and postmenopausal estrogen replacement therapy using a case-control design. We used the medical records-linkage system of the Rochester Epidemiology Project to identify 72 women who developed PD in Olmsted County, MN, during the twenty years 1976-1995. Each incident case was matched by age (+/- 1 year) to a general population control subject. We collected exposure data through review of the complete medical records of cases and control subjects in the system. PD cases had undergone hysterectomy (with or without unilateral oophorectomy) significantly more often than control subjects (odds ratio [OR] = 3.36; 95% confidence interval [CI] = 1.05-10.77). In addition, PD cases had experienced early menopause (< or = 46 years) more commonly than control subjects (OR = 2.18; 95% CI = 0.88-5.39). Finally, PD cases had used estrogens orally or parenterally for at least 6 months after menopause less frequently (8%) than control subjects (14%; OR = 0.47; 95% CI = 0.12-1.85). However, the findings for early menopause and estrogen replacement therapy were not statistically significant. Despite the limited sample size of this exploratory study, we hypothesize that there is an increased risk of PD in conditions causing an early reduction in endogenous estrogen. This hypothesis needs to be confirmed in a larger study.

Time trends in the incidence of parkinsonism in Olmsted County, Minnesota

OBJECTIVE

To investigate time trends in the incidence of parkinsonism and PD over a 15-year period (1976 to 1990).

METHODS

The authors used the medical records-linkage system of the Rochester Epidemiology Project to identify incidence cases of parkinsonism in Olmsted County, MN, over three 5-year periods, 1976 to 1980, 1981 to 1985, and 1986 to 1990. PD and other types of parkinsonism were classified using defined criteria. Population denominators were derived from census data and were corrected by removing prevalent cases of parkinsonism.

RESULTS

Over the 15 years of the study, 364 cases of parkinsonism were identified; 154 (42%) of them had PD. The incidence of parkinsonism remained stable over the three 5-year periods for the age classes 0 to 39, 40 to 59, and 60 to 69 years. For the age class 70 to 99 years, there was some increase over time mainly owing to an increased incidence of drug-induced parkinsonism. The incidence of PD remained stable over the three 5-year periods for all age classes. Results were similar when considering men and women separately. No birth-cohort effect was present for parkinsonism. Comparison with three previous studies in the same population did not reveal any major long-term secular trends in the incidence of parkinsonism.

CONCLUSIONS

The findings for PD over 15 years and comparison of the findings with historical data for parkinsonism over half a century suggest that no major environmental risk factors for PD (e.g., environmental toxins, drugs, diet constituents, or infectious agents) were introduced or removed from this population during these periods.

Smoking, alcohol, and coffee consumption preceding Parkinson's disease: a case-control study

OBJECTIVE

To study the association of PD with preceding smoking, alcohol, and coffee consumption using a case-control design.

METHODS

The authors used the medical records linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, MN, during the years 1976 to 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control subject. The authors reviewed the complete medical records of cases and control subjects to abstract exposure information.

RESULTS

For coffee consumption, the authors found an OR of 0.35 (95% CI = 0.16 to 0.78, p = 0.01), a dose-effect trend (p = 0.003), and a later age at PD onset in cases who drank coffee compared with those who never did (median 72 versus 64 years; p = 0.0002). The inverse association with coffee remained significant after adjustment for education, smoking, and alcohol drinking and was restricted to PD cases with onset at age <72 years and to men. The OR for cigarette smoking was 0.69 (95% CI = 0.45 to 1.08, p = 0.1). The authors found no association between PD and alcohol consumption. Extreme or unusual behaviors such as tobacco chewing or snuff use and a diagnosis of alcoholism were significantly more common in control subjects than cases.

CONCLUSIONS

These findings suggest an inverse association between coffee drinking and PD; however, this association does not imply that coffee has a direct protective effect against PD. Alternative explanations for the association should be considered.

Parkinson's disease and parkinsonism in a longitudinal study: two-fold higher incidence in men. ILSA Working Group. Italian Longitudinal Study on Aging

OBJECTIVE

To determine the incidence of parkinsonism and PD in the Italian elderly, and to explore the relation with age and gender.

METHODS

In eight Italian municipalities, a population-based, parkinsonism-free cohort was followed for an average of 3 years. At the end of the follow-up, the cohort survivors were directly contacted (screening and clinical examination). Cohort members who had died were studied using death certificates, clinical records, and information gathered from relatives and general practitioners. Parkinsonism diagnosis and subtyping were made according to specified diagnostic criteria.

RESULTS

The cohort consisted of 4,341 individuals (65 to 84 years of age): 596 died before the examination, 2,863 (76.4% of the survivors) completed the screening procedure, and 882 refused to participate. The authors found 68 incident cases of parkinsonism: 42 PD (62%), 7 drug-induced parkinsonism (10%), 8 parkinsonism in dementia (12%), 8 vascular parkinsonism (12%), and 3 parkinsonism, unspecified (5.8%). Average annual incidence rate (per 100,000 person-years) in the population aged 65 to 84 years, adjusted to the 1992 Italian population, was 529.7 (95% CI, 400.5 to 658.9) for parkinsonism, and 326.3 (95% CI, 224.1 to 427.5) for PD. Incidence rates for both parkinsonism and PD increased with age in both men and women; men had higher rates in every age group. Age-adjusted relative risk in men compared with women was 1.66 (95% CI, 1.02 to 2.70) for parkinsonism and 2.13 (95% CI, 1.11 to 4.11) for PD.

CONCLUSIONS

Incidence of parkinsonism and PD increased with age, PD was the most common type of parkinsonism, and men had a risk of developing PD twice that of women.

Pitfalls in neuroepidemiologic research

In neuroepidemiologic research, there are many pitfalls to trap unwary investigators, whether the project is a survey, a case-control study, or some other type of study. We briefly discuss pitfalls relating to: research preliminaries (e.g., failure to decide on study objectives); personnel and training (e.g., deficient training); data collection (e.g., ineffective supervision); data ownership and data sharing (disagreement about how the data will be used), and report preparation (e.g., failure to interpret results in the context of uncertainties arising from the design and implementation of the research). Awareness of these pitfalls will reduce the likelihood of flawed or ineffective neuroepidemiologic research.

Parkinson's disease, smoking, and family history. EUROPARKINSON Study Group

There is growing evidence that both genetic and environmental factors play a role in the etiology of Parkinson's disease (PD). The hypothesis of an interaction between genetic and environmental risk factors has been little explored, and never using a population-based case-control study design. Our objective was to investigate the possible interaction between smoking and family history in the etiology of PD, as part of a collaborative population-based case-control study. We included 149 nondemented PD patients ascertained in three European prevalence surveys using a two-phase design. Each patient was matched by age (+/-2 years), gender, and center to three controls drawn from the same populations (n=375). Presence of PD among first-degree relatives and smoking history were assessed through an interview for 127 cases and 306 controls. In the overall sample we found suggestive evidence that family history and ever-smoking interact in determining the risk of PD (P=0.09), with individuals exposed to both risk factors having the highest risk (OR=10.0; 95% CI=2.0-49.6). Analyses were repeated after stratification into two age-groups (cutoff: 75 years). In older patients, the joint exposure to both risk factors was associated with a significant increase in the risk of PD (OR=17.6; 95% CI=1.9-160.5). Among younger subjects, the OR for joint exposure was not significant. In conclusion, our findings suggest that smoking and family history interact synergistically on a multiplicative scale in determining the risk of PD in individuals older than 75 years.

Influence of strict, intermediate, and broad diagnostic criteria on the age- and sex-specific incidence of Parkinson's disease

We studied the influence of three sets of diagnostic criteria on the age- and sex-specific incidence of Parkinson's disease (PD) among residents of Olmsted County, Minnesota, for the period 1976 to 1990. Incidence cases of parkinsonism were detected using the medical records-linkage system of the Rochester Epidemiology Project. PD was separated from other types of parkinsonism using strict, intermediate, and broad criteria. We found 154 incident cases of PD using the strict criteria, 215 using the intermediate criteria, and 266 using the broad criteria. The incidence rate was consistently higher for men across all ages with all three sets of criteria; however, sex differences were more striking at older ages when using the broad criteria. In men above age 79 years, the incidence rate of PD declined with strict criteria, remained stable with intermediate criteria, and increased with broad criteria. The impact of diagnostic criteria on the age-specific incidence curve was less striking for women. When using the broad criteria, the risk of PD increased constantly with age in both sexes, suggesting that PD is an aging-related disease. Our findings suggest that the diagnostic criteria used to separate PD from other types of parkinsonism influence the magnitude of PD incidence and its distribution by age and sex.

Prevalence of dementia in the rural village of Hanazono-mura, Japan

We studied the prevalence of dementing disorders in a rural municipality of Japan (Hanazono-mura), using a door-to-door two-phase design. In phase 1, the Hasegawa's Dementia Scale-Revised was applied as a screening test to all subjects aged 65 years and older (n = 201). Among subjects screened positive, 17 were diagnosed with dementia in phase 2. The prevalence (cases/100 aged 65 years and older) was 8.5 for all types of dementia, 3.5 for Alzheimer's disease, 3.0 for vascular dementia, and 2.0 for other dementia (including mixed dementia). The prevalence of dementia was slightly but consistently higher in men than women at all ages. The overall prevalence was higher in women for Alzheimer's disease and in men for vascular dementia.

Anxiety disorders and depressive disorders preceding Parkinson's disease: a case-control study

We studied the association between preceding psychiatric disorders and Parkinson's disease (PD) using a case-control design. We used the medical records-linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, Minnesota, during the years 1976-1995. Each case was matched by age (+/-1 yr) and sex to a general population control. We reviewed the complete medical records of cases and control subjects to detect preceding psychiatric disorders. The frequency of psychiatric disorders was higher in cases than in control subjects; the odds ratio was 2.2 for anxiety disorders (95% confidence interval [95% CI] = 1.4-3.4; p = 0.0003), 1.9 for depressive disorders (95% CI = 1.1-3.2; p = 0.02), and 2.4 for both anxiety disorders and depressive disorders occurring in the same individual (95% CI = 1.2-4.8; p = 0.02). When we restricted analyses to disorders present 5 years or more before the onset of motor symptoms of PD, the association with depressive disorders lost statistical significance. However, the association with anxiety disorders remained significant for disorders present 5, 10, or 20 years before onset of motor symptoms. Our results suggest that anxiety disorders and depressive disorders are associated with PD and that the causative process or the risk factors underlying PD are present many years before the appearance of motor symptoms.

Case-control study of debrisoquine 4-hydroxylase, N-acetyltransferase 2, and apolipoprotein E gene polymorphisms in Parkinson's disease

We investigated the association of Parkinson's disease (PD) with two genes encoding liver-detoxifying enzymes, debrisoquine 4-hydroxylase (CYP2D6) and N-acetyltransferase 2 (NAT2), and with one gene related to Alzheimer's disease, apolipoprotein E (APOE). In a sample of 139 unrelated PD cases and 113 control subjects, the NAT2 M3 allele was associated with PD (odds ratio = 7.9; 95% confidence interval = 1.7-36.3). Case-control analyses for CYP2D6, APOE, and NAT2 M1 or M2 did not show a significant association. However, the age at onset of PD was significantly earlier in cases with the APOE epsilon2/epsilon3 genotype than in cases with the epsilon3/epsilon3 genotype.

Incidence of medically recognized migraine: A 1989-1990 study in Olmsted County, Minnesota

OBJECTIVE

To investigate the incidence of medically recognized migraine in Olmsted County, Minnesota, during the years 1989 to 1990.

METHODS

We used the records-linkage system of the Rochester Epidemiology Project to identify all subjects who sought medical attention for their headache and had their initial visit for migraine within the study period. Incident cases were classified using specified criteria.

RESULTS

From 9837 records screened, we found 713 incident cases. The average annual incidence rate (new cases per 100 000 person-years) was 343.0 in both sexes combined, 481.6 in women, and 194.4 in men. In women, incidence rates were low at the extremes of age and higher among those aged between 10 and 49 years, with a striking peak at the age of 20 to 29 years. Migraine without aura was the most common type of migraine in women. Men had a more constant risk of migraine throughout life with a lesser peak at the age of 10 to 19 years, and they were equally affected by all types of migraine. Women had consistently higher incidence rates than men at all ages, and there were strikingly higher incidence rates of migraine without aura in women than in men.

CONCLUSIONS

Although our incidence rates were restricted to medically recognized cases of migraine, we confirmed previously reported epidemiological patterns.

The cost of epilepsy in the United States: an estimate from population-based clinical and survey data

PURPOSE

To provide 1995 estimates of the lifetime and annual cost of epilepsy in the United States using data from patients with epilepsy, and adjusting for the effects of comorbidities and socioeconomic conditions.

METHODS

Direct treatment-related costs of epilepsy from onset through 6 years were derived from billing and medical chart data for 608 population-based incident cases at two sites in different regions of the country. Indirect productivity-related costs were derived from a survey of 1,168 adult patients visiting regional treatment centers. Direct costs separate the effects of epilepsy and comorbidity conditions. Indirect costs account for the effects of other disabilities and socioeconomic conditions on foregone earnings and household activity. The estimates were applied to 1995 population figures to derive national projections of the lifetime and annual costs of the disorder.

RESULTS

The lifetime cost of epilepsy for an estimated 181,000 people with onset in 1995 is projected at $11.1 billion, and the annual cost for the estimated 2.3 million prevalent cases is estimated at $12.5 billion. Indirect costs account for 85% of the total and, with direct costs, are concentrated in people with intractable epilepsy.

CONCLUSIONS

Direct costs attributable to epilepsy are below previous estimates. Indirect costs adjusted for the socioeconomic conditions of patients are above previous estimates. Findings indicate that epilepsy is unique in the large proportion of costs that are productivity-related, justifying further investment in the development of effective interventions.

Incidence of epileptic syndromes in Rochester, Minnesota: 1980-1984

PURPOSE

To determine the incidence and the distribution of epileptic syndromes in a well-defined population.

METHODS

By using the records-linkage system of the Rochester Epidemiology Project, we screened all the residents of Rochester, Minnesota, who received a diagnosis of seizures, convulsions, or epilepsy from 1980 through 1984. One hundred fifty-seven residents with incident epilepsy (recurrent unprovoked seizures) were classified by using the International League Against Epilepsy (ILAE) Classification of the Epilepsies and Epileptic Syndromes. Residents with special syndromes were excluded. With a pretested algorithm, patients were classified at three levels of specification: major syndromic groups (e.g., localization-related syndromes), syndromic subgroups (e.g., idiopathic epilepsy with age-related onset), and whenever possible, individual syndromes.

RESULTS

All but one patient were classified into major syndromic groups and subgroups. The annual age-adjusted incidence per 100,000 population was 52.3 cases (34.9 for localization-related epilepsies; 7.7 for generalized epilepsies; 9.7 for undetermined epilepsies). Incidence was 0.2 for idiopathic, 17.2 for cryptogenic, 17.5 for symptomatic localization-related epilepsies, 3.7 for idiopathic, 1.7 for symptomatic or cryptogenic (age-related), and 2.3 for symptomatic (non age-related) generalized epilepsies.

CONCLUSIONS

With the exception of idiopathic epilepsies, the incidence of the major syndromic categories in our study was higher than that provided by previous population-based studies.

Case-control study of the ubiquitin carboxy-terminal hydrolase L1 gene in Parkinson's disease

We investigated the association of PD with a recently reported I93M mutation of the ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) gene, and with a new and common polymorphic variant S18Y of the same gene. We did not identify the I93M mutation in any of 139 unrelated PD cases or 113 controls. However, S18Y polymorphism carriers had significantly lower risk of PD (odds ratio = 0.53; p = 0.03), and the risk reduction was greater for younger onset cases.

Increasing incidence of medically recognized migraine headache in a United States population

OBJECTIVE

To investigate trends in the incidence of medically recognized migraine in Olmsted County, Minnesota over approximately a decade.

METHODS

The authors used the records-linkage system of the Rochester Epidemiology Project to identify individuals whose records included any diagnostic rubric related to headache for the 3-year period 1979 through 1981 and the 2-year period 1989 through 1990. A nurse abstracter and a neurologist (J.W.S.) reviewed the complete history of each potential case and assigned a diagnosis using the International Headache Society classification (IHS, modified). Only patients who consulted a doctor for their headache and had their initial visit for migraine within the study years were considered as incident cases.

RESULTS

The incidence of medically recognized migraine increased in female subjects between the 1979-through-1981 period and the 1989-through-1990 period for all ages, but particularly among those who were aged 10 to 49 years. The peak incidence rate at age 20 to 29 years increased from 634.5 new cases per 100,000 person-years in 1979 through 1981 to 986.4 in the 1989-through-1990 period (absolute increase 351.9; relative increase 56%). The rise in incidence in female subjects was most sizable for migrainous disorder (IHS code 1.7); smaller increases were noted for migraine without aura and with typical aura. Only a slight absolute increase in migraine incidence rates was observed in male subjects, restricted to those 10 to 19 years of age (absolute increase 174.7; relative increase 89%).

CONCLUSIONS

Although the incidence rates reported here are restricted to patients who consulted a doctor for their headache, the authors suggest that the incidence of migraine has increased over time in female subjects, especially those of reproductive age. The increase was most pronounced for migrainous disorder. Incidence rates were more stable in male subjects over time.

Autopsy patterns for Parkinson's disease and related disorders in Olmsted County, Minnesota

Using a records-linkage system, we determined the frequency and distribution of brain autopsies in residents of Olmsted County, Minnesota, in whom parkinsonism developed during 1976 through 1990. Of the 364 incident cases identified, 235 patients were deceased at the time of record abstraction. The overall autopsy rate was low (23%). Diagnostic certainty (for PD), diagnostic type (PD versus other parkinsonism), sex, age at death, and location at death were important selection factors for autopsy.

Frequency and distribution of vascular dementia

It remains difficult to draw conclusions about the frequency and distribution of vascular dementia (VaD). The data from current studies cannot be compared and reconciled easily. Disagreement on diagnostic criteria and their field implementation remains the major problem. In particular, there is uncertainty about the classification of patients who show both vascular and degenerative features, about the advantages and disadvantages of using brief clinical scales (e.g., the Hachinski Ischemic Score), about the use of imaging findings in defining VaD, and about the minimal level of severity to be included in epidemiologic studies. Nevertheless, we can tentatively summarize current epidemiologic data in four points. (1) Both the prevalence and the incidence of VaD increase steeply with age. (2) The prevalence of VaD is generally higher among men than among women; the sex difference is more controversial for incidence. (3) There are sizeable differences in both incidence and prevalence across countries. (4) A declining trend in both the prevalence and the incidence of VaD was reported from one population; however, the decline was restricted to the age class 80-89 years. No trends data are available after the 1970s.

Prevention of vascular dementia

Stroke is an important public health problem worldwide. Those at high risk of stroke may be at high risk of cognitive impairment and dementia after stroke. Modifiable cardiovascular risk factors in midlife including hypertension, alcohol use, cigarette smoking, and certain dietary factors may be important targets for prevention of vascular causes of cognitive impairment. These same types of factors may also be associated with Alzheimer disease. Better control of cardiovascular disease risk factors might lead to delay or prevention of vascular dementia and Alzheimer disease.

Detection of preclinical Parkinson disease in at-risk family members with use of [123I]beta-CIT and SPECT: an exploratory study

OBJECTIVE

To explore whether the radioligand 2 beta-carboxymethoxy-3 beta-(4-[123I] iodophenyl) tropane ([123I]beta-CIT) and single-photon emission computed tomography (SPECT) can detect decreased striatal uptake in at-risk relatives of patients with Parkinson disease (PD).

PATIENTS AND METHODS

Ten PD patients, 10 at-risk first-degree relatives of PD patients, and 10 controls underwent [123I]beta-CIT and SPECT brain imaging. Their striatal uptake ratios were compared.

RESULTS

Age-adjusted specific to nonspecific striatal uptake ratios were lower in patients compared with controls and with relatives; however, ratios were similar in relatives and controls. Among relatives, ratios were consistently lower in subgroups postulated to be at higher risk for preclinical PD.

CONCLUSION

Our findings provide preliminary support that [123I]beta-CIT and SPECT may detect decreased striatal uptake in relatives of PD patients postulated to be at higher risk for PD.

Familial aggregation of Parkinson's disease: a population-based case-control study in Europe. EUROPARKINSON Study Group

OBJECTIVE

To investigate the familial aggregation of PD in a large collaborative population-based case-control study.

BACKGROUND

Most previous case-control studies of the familial aggregation of PD have been hospital- or clinic-based.

METHODS

We included 219 prevalent cases ascertained in three European populations (centers), using a two-phase design consisting of screening and examination by a neurologist. Each case was matched by age, sex, and center to three controls drawn from the same populations (n = 657). Presence of PD among first-degree relatives (parents and siblings) was determined using the family history approach for 175 cases and 481 controls.

RESULTS

Overall, a positive family history (at least one parent or sibling affected by PD) was reported in 10.3% of patients and 3.5% of controls (odds ratio [OR] = 3.2; 95% confidence interval [CI] = 1.6 to 6.6). A similar association was observed when analyses were restricted to nondemented patients and controls (OR = 3.9; 95% CI = 1.7 to 8.7) or to newly diagnosed patients (OR = 3.3; 95% CI = 0.9 to 11.9). We found a significant trend of increasing risk with increasing number of affected relatives (p = 0.003). Analyses stratified by age showed a stronger association for younger PD patients (OR = 7.6; 95% CI = 1.5 to 38.9) than for older patients (OR = 2.5; 95% CI = 1.1 to 5.7).

CONCLUSIONS

In this large sample of prevalent PD patients and population-matched controls, PD significantly aggregates in families, with the strength of the association being age-dependent. Therefore, familial factors, which can be genetic, environmental, or both, play a role in PD.

The incidence and prevalence of myoclonus in Olmsted County, Minnesota

OBJECTIVE

To study the incidence and prevalence of diagnosed myoclonus in Olmsted County, Minnesota. Little is known about the frequency and distribution of myoclonus in the general population.

DESIGN

Descriptive study with case ascertainment through a records-linkage system.

PATIENTS AND METHODS

We used a medical records-linkage system to identify all subjects whose records contained documentation of myoclonus or of diseases known to exhibit myoclonus. The records of all potential patients were reviewed by a neurologist, and only patients with pathologic and persistent myoclonus were included. Population denominators were derived from census data.

RESULTS

The average annual incidence rate of pathologic and persistent myoclonus for 1976 through 1990 was 1.3 cases per 100,000 person-years. The rate increased with advancing age and was consistently higher in men. Symptomatic myoclonus was the most common type, followed by epileptic and essential myoclonus; dementing diseases were the most common cause of symptomatic myoclonus. The lifetime prevalence of myoclonus, as of January 1, 1990, was 8.6 cases per 100,000 population, and the prevalence increased with advancing age.

CONCLUSION

Although our figures are probably under-estimated, they are the first attempt, to our knowledge, to measure myoclonus morbidity in the general population. We found clinical features and age and sex distributions different from those previously described in clinical series.