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Background: No data exist on whether the syndrome of amnestic mild cognitive impairment occurs in the oldest old, or if the relationships for functional status and neuropsychometric performance based on clinical diagnosis hold true in this age group., Design/methods: The authors performed comprehensive neurologic evaluations, neuropsychometric testing, and functional assessments on a sample of 90- to 100-year-old residents of Rochester, MN. Subjects were diagnosed as normal or with amnestic mild cognitive impairment (MCI) or dementia according to well-accepted criteria. Data on the following measures were collected and analyzed: Record of Independent Living (ROIL), Mini-Mental State Examination (MMSE), Dementia Rating Scale (DRS), Trailmaking Test (TMT), and modified version of the Free and Cued Selective Reminding Test (FCSRT)., Results: Data on 111 subjects (56 normal, 13 MCI, and 42 dementia) were analyzed. On the ROIL, functional capacity to carry out activities of daily living was worse for patients with dementia compared to patients with MCI and normal subjects, but did not differ between MCI and normal subjects. Scores on the MMSE, DRS, and TMT-A were worse in the dementia group compared to the normal group, and in the dementia group compared to MCI, but scores on these measures for normal subjects compared to patients with MCI were not different. Scores on the FCSRT and memory subtest of the DRS showed differences among all three groups., Conclusion: In spite of the advanced age of the cohort, the relationship between cognitive and functional performance and clinical diagnosis follows patterns previously described in younger samples of normal subjects, subjects with amnestic mild cognitive impairment, and subjects with dementia.

Objective: To investigate the relationship between features and definitions of vascular dementia (VaD) and survival., Design: We used the medical records linkage system of the Rochester Epidemiology Project to identify incident cases of dementia in Rochester from January 1, 1985, through December 31, 1989. Dementia and Alzheimer disease were defined using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Vascular dementia was defined by ad hoc criteria, including imaging. Each patient with dementia was matched by age and sex to a referent subject free of dementia. Patients with dementia and referent subjects were followed from the onset of dementia (or index year) through death, censoring, or the end of the study., Results: We included 479 patients with incident dementia and 479 referent subjects. Overall, patients with VaD had worse mortality than referent subjects (relative risk [RR], 2.7; 95% confidence interval [CI], 1.9-3.9). Among patients with VaD, those with dementia temporally related to a stroke had a worse relative mortality (RR, 4.5; 95% CI, 2.7-7.4) than those with only imaging evidence of bilateral infarctions in gray matter structures (RR, 2.4; 95% CI, 1.5-3.8). Relative mortality estimates varied by using 3 sets of published diagnostic criteria for VaD. Patients with VaD had a higher RR of death (RR, 2.7; 95% CI, 1.9-3.9) than patients with dementia overall (RR, 1.8; 95% CI, 1.6-2.1) or patients with Alzheimer disease (RR, 1.4; 95% CI, 1.2-1.7)., Conclusions: The relative mortality of patients with VaD varied depending on the set of diagnostic criteria used. A temporal relationship to a stroke was the strongest predictive feature for poor survival in patients with dementia.

Background: Incidence rates of Alzheimer disease (AD) were higher in women than in men in several recent European and Asian studies. Cohort studies in the United States, on the other hand, have consistently reported no difference in incidence across sex., Objective: To measure age- and sex-specific incidence rates of dementia and AD for persons aged 50 years and older residing in Rochester, Minn, during 1985 to 1989., Subjects and Methods: Cases were ascertained through the medical records linkage system of the Rochester Epidemiology Project, which encompasses the records of all medical care providers (including outpatient clinics, hospitals, general practitioners, and nursing homes) in Rochester. Computer indices of clinical diagnoses, histologic diagnoses, and medical procedures were screened for indications of dementia. All medical records of potential cases were reviewed and abstracted by a trained nurse abstractor. A neurologist (E.K.) confirmed the presence of dementia and established a differential diagnosis of AD using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and estimated the year of onset., Results: A total of 482 incident cases of dementia were identified; 356 of them (73.9%) had AD. For both dementia and AD, incidence rates increased steeply with age, and there were no consistent differences between men and women. The sex pattern for AD did not change after removing cases with silent bilateral infarcts on imaging., Conclusions: Contrary to observations from European and Asian populations, women were not at increased risk of incident AD in Rochester. Our findings, based on a medical records linkage system, corroborate findings from several other US studies that involved the direct contact of cohort members. The consistency of findings across study designs suggests that sex or sex-related exposures do not consistently play a major role in AD causation in American populations.

Objective: To examine the contribution of cerebrovascular disease to dementia., Methods: We used the records-linkage system of the Rochester Epidemiology Project to ascertain incident cases of dementia in Rochester, Minn, for 1985 through 1989. We defined dementia using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. To define dementia types, we reviewed neuroimaging reports, which were available for two thirds of dementia cases, in addition to medical histories and neurologic examination results. Vascular dementia (VaD) was defined by 1 of the following criteria: dementia onset or worsening within 3 months of a clinical stroke or bilateral gray matter infarctlike lesions shown by imaging that fulfilled specified location criteria (critical imaging lesions)., Results: We found 482 incident cases of dementia. Overall, 10% of patients had onset or worsening of their dementia within 3 months of a stroke. Eleven percent of the incident dementia cases had bilateral gray matter lesions on imaging that were considered critical. Eighteen percent of patients had one or the other of these features (VaD by our criteria), but only 4% of patients had both. The incidence rate of VaD increased steeply with advancing age and was similar in men and women. Our incidence rates were similar to those from a recent European meta-analysis., Conclusion: The presence of either a stroke temporally related to dementia onset or worsening or of critical imaging lesions was common among dementia patients, whereas the occurrence of both features together was rare.

Objective: To examine risk factors for nursing home placement in a population-based dementia cohort., Methods: The Mayo Clinic Medical Records linkage system was used to identify all patients with onset of dementia between 1980 and 1984. The patient group included 314 cases who met DSM-III-R criteria for dementia, including 220 cases who were community dwelling at onset. All dementia patients were followed until death. A control group included 323 patients who did not, at any point, meet DSM-III-R criterion for dementia. The groups were initially matched on age, gender, and year of initial registration. Demographic, medical, social, and functional predictors were examined as static and time-dependent risk factors for nursing home placement in the initial community-dwelling subgroups, using stepwise Cox regression modeling., Results: Of the 314 dementia patients, 282 took residence in licensed skilled nursing homes for at least 6 weeks, suggestive of custodial care, at some point during the course of their illness. In the control group, 162 of the 323 people required nursing home placement. Within controls, the predictor variables of time to nursing home placement included initial age, being divorced, living in a townhome, apartment or assisted living apartment, change in Charlson comorbidity score, and change in amount of daily assistance required. Within the dementia sample, seven predictors were eventually determined to be associated with time to nursing home placement. These included total number of years of education, age at onset of dementia, being single, living in a retirement or supervised apartment at onset, change in Charlson comorbidity score, and a change in the amount of daily assistance required., Conclusions: Cumulative incidence of placement was 90% in the dementia cohort and 50% in the controls. Certain variables seem to impact time to nursing home placement in all older persons, whether they have dementia or not. Among these are age, living in assisted living settings, increasing comorbidity scores, and increasing need for functional assistance. Certain additional factors may have a specific impact in dementia. Among these is education, which seems to provide a protective effect. These predictors may be important covariates in clinical dementia studies that include time to nursing home placement as an outcome variable.

Objective: To study the association between estrogen replacement therapy in postmenopausal women and AD using a case-control design., Background: Studies of the effect of estrogen therapy on the risk of AD have been limited and have yielded conflicting results., Methods: Case patients were all postmenopausal women who developed AD in the quinquennium 1980 through 1984 in Rochester, MN (n = 222). One control subject from the same population and free of dementia was matched to each case patient by age (+/-3 years) and length of enrollment in the records-linkage system (n = 222). Estrogen exposure was defined as any form of estrogen (oral, parenteral, topical, suppository) used for at least 6 months after the onset of menopause and before the onset of AD (or corresponding year in the matched control subject). Information on dose and duration of use was abstracted. Consistent with the matched design, analyses entailed conditional logistic regression., Results: AD patients and control subjects had identical age at menarche (median: 13.0 versus 13.0 years) and age at menopause (median: 50.0 versus 50.0 years). The frequency of estrogen use was higher among control subjects than AD patients (10% versus 5%; odds ratio = 0.42; 95% confidence interval 0.18 to 0.96; p = 0.04). There was a significant trend of decreasing odds ratios with increasing duration of use. The inverse association between estrogen therapy and AD remained significant after adjustment for education and age at menopause., Conclusion: These results from a population-based study suggest that estrogen replacement therapy is associated with a reduced risk of AD in postmenopausal women.

For both dementia and Alzheimer's disease (AD), data regarding incidence rates in the oldest old and time trends in incidence are limited. The authors reanalyzed previously reported data on the incidence of dementia and AD in Rochester, Minnesota, from 1975 through 1984, using three new strategies. First, incidence rates were corrected by removing age-, sex-, and calendar year-specific prevalent cases from the census-derived denominator figures. Second, incidence figures for persons above age 84 years were disaggregated. Third, time trends were investigated graphically using age-specific curves and birth cohort curves. Dementia diagnosis and AD diagnosis followed defined ad hoc criteria. Analyses were conducted for men, women, and both sexes combined, and for dementia and AD separately. The age-specific incidence rates were similar in men and women, continued to increase after age 84 years, and remained stable over time for both dementia and AD. No birth cohort effect was present for either dementia or AD. The similar risks seen in men and women, the continuing increase in incidence after age 84 years, and the stability of incidence over time have important implications for etiologic research on AD.

To further investigate the relationship between psychiatric disorders and dementia in elderly patients, the authors drew a population-based, age-stratified random sample from residents of Rochester, Minnesota, age 65 and older. A trained paramedic completed a 90-minute screening interview, including the Symptom Checklist-90, Mini-Mental State Exam, and Auditory-Verbal Learning Test. Persons failing the screens were interviewed by a psychiatrist and a neurologist. DSM-III-R diagnoses were assigned for dementia and other psychiatric disorders. Of 201 participants, 37 were evaluated further by both neurologist and psychiatrist. One received a psychiatric diagnosis alone. Dementia alone was present in four people. Concurrent psychiatric diagnoses and dementia were found in 17 subjects. Much of the psychopathology found in older persons occurs in people with cognitive impairment. Current diagnostic nosology may not be able to capture the interrelatedness of psychiatric syndromes and cognitive impairment in elderly patients.

Purpose: To evaluate the association, if any, between Alzheimer's disease (AD) and anemia among the elderly., Methods: Both case-control and cohort methodologies were used to evaluate this association. The case-control study included all incident cases of AD whose onset occurred during 1980-1984 in Rochester, MN (n = 302). An age- and gender-matched control was selected from among Rochester residents seen for care at Mayo Clinic during the year of onset of the case. All community medical records for cases and controls were reviewed to identify women with hemoglobin levels of < 12 g/dL and men with hemoglobin levels of < 13 g/dL during the year of onset and the prior year for cases and during the index year and year prior for controls. Logistic regression was used to estimate odds ratios (OR). The retrospective cohort study used the 618 residents of Olmsted County, MN, who were > or = 65 years of age and whose anemia, as defined above, was newly recognized in 1986. Standardized incidence ratios (SIR) for AD were estimated by use of the person-years of follow-up in the cohort and the incidence rates of AD for this community., Results: In the case-control study, an almost twofold increase in occurrence of AD was associated with anemia (OR, 1.88; 95% CI, 1.17-3.03). For men and women, respectively, the ORs were 1.81 (95% CI, 0.75-4.39) and 1.96 (95% CI, 1.11-3.47). The cohort study showed no overall increase in risk of AD (SIR, 0.98; 95% CI, 0.67-1.37). For men, the SIR was a comparable 1.49 (95% CI, 0.79-2.56), whereas for women the SIR was only 0.79 (95% CI, 0.49-1.23)., Conclusions: Although anemia may be a risk factor for AD in the elderly, the mechanism by which anemia contributes to the pathogenesis of AD or to the unmasking of AD symptoms is unknown.

It is unclear whether persons with diabetes are at increased risk for dementia, including Alzheimer's disease. Existing studies are limited by small sample size, selection bias, and case-control designs. This population-based historical cohort study provides estimates of the risk of dementia and Alzheimer's disease associated with adult onset diabetes mellitus (AODM). The sample included all persons with AODM residing in Rochester, Minnesota, on January 1, 1970, plus all persons diagnosed in Rochester or who moved to Rochester with the diagnosis between January 1, 1970, and December 31, 1984. Individuals were followed through review of their complete medical records from AODM diagnosis until dementia onset, emigration, death, or January 1, 1985. Standardized morbidity ratios for dementia and Alzheimer's disease were calculated, using an expected incidence based on age- and sex-specific rates for the Rochester population. Poisson regression was used to estimate risks for persons with AODM relative to those without. Of the 1,455 cases of AODM followed for 9,981 person-years, 101 developed dementia, including 77 who met criteria for Alzheimer's disease. Persons with AODM exhibited significantly increased risk of all dementia (Poisson regression relative risk (RR) = 1.66, 95% confidence interval (CI) 1.34-2.05). Risk of Alzheimer's disease was also elevated (for men, R = 2.27, 95% CI 1.55-3.31; for women, RR = 1.37, 95% CI 0.94-2.01). These findings emphasize the importance of AODM prevention and prompt additional investigation of the relation between AODM and dementia.

Cause of death among 917 of the 959 subjects in a population-based incidence cohort with Alzheimer's disease (AD) during the years 1960 to 1984 was compared to that of an age- and gender-matched control group (n = 703). In general, a summary of the diagnostic codes entered anywhere on a death certificate suggests that control subjects had more cardiovascular disease and neoplasms than did patients, while patients more often had a diagnostic code of bronchitis/pneumonia (P < 0.01). By logistic regression, this difference remained statistically significant after adjusting for age and gender.

Objective: To present the results of several retrospective epidemiologic studies of dementia in Rochester, Minnesota., Material and Methods: These studies were done by using the medical records-linkage resources of the Rochester Epidemiology Project., Results: The incidence and prevalence of dementia increase sharply with advancing age. No difference is noted in overall age-adjusted incidence rates by gender. Rochester studies provide the only 25-year time trend analyses of the incidence of dementia in the United States. Time trends over three prevalence dates indicate an increase in prevalence in this community. Survival is decreased among patients with dementing illness. Case-control studies of Alzheimer's disease (AD) show that general medical conditions, previous head injury, thyroid disease, exposure to therapeutic radiation, anesthesia, and blood transfusion are generally not risk factors for AD. Patients with depression may have an increased risk for the development of AD. Sociodemographic factors such as education, occupation, marital status, and type of dwelling were not significantly different among patients with AD and their age-and gender-matched control subjects., Conclusion: The Rochester Epidemiology Project has proved to be an excellent resource for the study of the incidence, prevalence, and risk factors for dementia.

Objective: A retrospective, population-based, case-control study was carried out to evaluate episodes of prior intra-operative hypotension as a potential risk factor for Alzheimer's disease (AD)., Methods: Patients were all incident cases of AD from 1975-1984 who resided for 40 years or more in Olmsted County prior to their onset of dementia (N = 252). One age and gender-matched control for each case was selected from all registrations for care at Mayo Clinic during the year of onset in the incident case. Each case and control group had 252 individuals., Results: Of these, 27 cases and 32 controls had at least one ten minute or longer episode of intra-operative hypotension of a systolic blood pressure of less than 90 mm Hg prior to the year of onset of dementia in the matched AD patient. We did not find a significantly increased risk of AD for hypotensive episodes of less than 75 or 90 mm Hg., Conclusions: It is unlikely that intra-operative hypotensive events of this degree increase the risk of AD.

We used the medical records linkage system for the population of Rochester, Minnesota, to identify persons in the community who had their first cerebral infarct without previous dementia. In this cohort (n = 971), the incidence of dementia in the first year was nine times greater than expected, but if we did not observe dementia in the first year, the risk of dementia in the cohort each year thereafter was about twice the risk in the population. After the first year, a 50% increase was observed in Alzheimer's disease in the cohort compared with that in the community. Although the incidence of dementia increased with increasing age, the standardized morbidity ratios decreased with increasing age. Age, sex (male), and second stroke were significant independent predictors of dementia in a multivariate Cox proportional hazards model. There was no effect of location or clinical severity of infarct on the rate of occurrence of dementia.

Resources of the Rochester Epidemiology Project were used to estimate prevalence rates for dementia on January 1, 1975, 1980, and 1985, and to evaluate trends over time. Prevalence rates increased with age for both men and women. There was no difference in the prevalence rates for January 1, 1975, and January 1, 1980, but there was a significant increase between January 1, 1980, and January 1, 1985. Similar results were found for Alzheimer's disease. Age was an important factor in the trend data. The apparent increase in prevalence over time is probably multifactorial.

We report the survival experience of the incidence cohort of Alzheimer's disease (AD) patients in Rochester, Minnesota, whose onset occurred during the years 1960 to 1984. Survival was evaluated relative to year of onset, age at onset, and gender. Survival was better among women than men and improved for those with AD with more recent onset. The relative hazard decreased by a factor of 0.82 for each decade. The effect of age at onset was nonlinear, indicating that the hazard of death does not change at a constant rate with age.

Objective: To calculate average annual incidence rates for Huntington's disease (HD) from 1950 through 1989 and to estimate prevalence rates of the disease for January 1, 1960, and January 1, 1990., Design: Health care records from all sources, including hospitals, outpatient clinics, and long-term care institutions, are readily available for all inhabitants of Olmsted County, Minnesota. The diagnoses entered in these records have been coded and indexed. All health care records containing a diagnosis that might suggest HD were reviewed, and those patients for whom the symptoms of HD began between January 1, 1950, and December 31, 1989, were identified. We used specific criteria for diagnosing HD., Participants: Health care records were reviewed; residence in Olmsted County during the year of symptom onset was required., Main Outcome Measures: Average annual incidence rates and prevalence rates for January 1, 1960, and January 1, 1990., Results: Overall incidence rates were 0.4 (95% confidence interval [CI], 0.1 to 0.8) for women and 0.2 (95% CI, 0.04 to 0.6) for men per 100,000 person-years. Estimated prevalence rates for January 1, 1960, per 100,000 person-years were 6 (95% CI, 0.7 to 21.5) for women and 6.6 (95% CI, 0.8 to 23.8) for men. For January 1, 1990, the prevalence rates were 1.8 (95% CI, 0.04 to 10.2) for women and 2 (95% CI, 0.05 to 10.9) for men., Conclusions: Incidence and prevalence rates of HD in this community are similar to those reported in other communities. The small numbers of affected persons do not allow an estimate of variation over time.

We performed a population-based, case-control study to evaluate prior blood transfusion as a potential risk factor for Alzheimer's disease (AD). All cases were incident cases of AD from 1975 to 1984 with residence for 40 years or more in Olmsted County, Minnesota, prior to their onset of dementia (N = 252). There was one age- and gender-matched control for each case. We ascertained the number of blood transfusions prior to the age of onset of dementia and the corresponding year in each control. Sixty-five cases and 55 controls had at least one prior blood transfusion. We did not find a significantly increased risk of AD for the events of at least one, three, or six blood transfusions.

Objective: To assess the risk of fracture following onset of Alzheimer's disease., Design: Retrospective (historical) cohort study., Setting: Population-based in Rochester, Minnesota., Participants: All 543 Rochester residents with onset of Alzheimer's disease during the 10-year period, 1975-84, and an equal number of age- and sex-matched controls from the community., Measurements: Fractures were assessed through review of each subject's complete (inpatient and outpatient) medical records in the community., Main Results: Rochester residents with Alzheimer's disease were no more likely to have a history of fracture prior to onset than were matched controls from the same population. During the year of onset, there was a 2-fold excess of fractures at various sites among those with Alzheimer's disease. The risk ratio for any fracture subsequently was 1.1 (95% CI 0.9, 1.3), and this slight increase was accounted for entirely by a 2.7-fold increase in the risk of hip fracture (95% CI 1.8, 4.2)., Conclusions: Fracture risk was not increased before the onset of Alzheimer's disease, although there was an excess of fractures around the time that Alzheimer's disease came to clinical attention. Fracture risk was not elevated thereafter except for a substantial increase in the risk of hip fracture. This suggests a link with certain falls rather than generalized disuse osteoporosis.

We performed a time trend study of incidence of dementing illness in Rochester, Minnesota. We ascertained age- and sex-specific incidence rates for the five quinquennia, 1960 through 1984. The incidence rates sharply increased with advancing age, reaching a high of 2,922/100,000 person years in the group 85 years and older. For dementia caused either solely or predominantly by Alzheimer's disease, this figure was 2,600/100,000 person years for the oldest age group. There were no significant differences in the incidence of dementing illness between men and women. In the oldest age groups in the last two quinquennia of study, there appears to be a trend toward increasing incidence rates. Over the years, the proportion of cases attributed to dementia due to unknown causes has decreased while the proportion of cases attributed to Alzheimer's disease has increased.

We compared the point prevalence rates of dementing illnesses in the population of Rochester, Minnesota, on January 1, 1980, with the previously published rates of January 1, 1975, by using extensive health care records available from all sources of care in the community, in order to identify and classify cases with standard diagnostic criteria derived from DSM-III. The overall age- and sex-adjusted prevalence rate per 100,000 population for dementia on January 1, 1980, was 402.5 compared with 388.4 on January 1, 1975; for Alzheimer's disease it was 259.8 in 1980 and 259.5 in 1975. The stability of the rates suggests no change in the incidence and mortality associated with these conditions. The prevalence rates for Rochester, Minnesota, are similar to many other rates estimated in other North American communities, but they differ from two other population-based estimates from East Boston and California. Case definitions and methods of assessment probably account for the differences in estimated prevalence.

To determine whether an association exists between Alzheimer's disease (AD) and thyroid disease, we carried out two studies in the population of Rochester, Minnesota. We reviewed medical records of a cohort of 198 women with histologically confirmed Hashimoto's thyroiditis (1935 to 1974) for evidence of subsequent dementia, applying the criteria used for dementia in a previous determination of incidence and prevalence rates in this population. From a total of 4,197 person-years of follow-up, eight cases of AD were diagnosed, whereas the expected number was 5.8. The standardized morbidity ratio was 1.37, which failed to reach statistical significance. The second study was a retrospective case-control comparison that sought any relationship between AD and all thyroid disorders, using a previously identified (1960 to 1979) AD cohort (N = 646) and their age- and sex-matched controls. For myxedema there was a positive association for AD without significance, whereas in Graves' disease there was a significant negative association for AD.

We reviewed the medical records of 821 Olmsted County residents who had suffered head trauma with presumed brain injury between 1935 and 1974 and were more than 40 years old at the time of their last medical assessment. These patients were followed over 15,000 person-years for dementia and other degenerative neurologic diseases. The standardized morbidity ratio (SMR) for dementia was 1.06, and the SMR for dementia of the Alzheimer type was 1.00. These values are not significantly elevated and are inconsistent with studies that suggest that head trauma is a risk factor for Alzheimer's disease. In addition, the SMRs for parkinsonism (1.04), Parkinson's disease (0.94), and amyotrophic lateral sclerosis (1.05) were not significantly elevated, providing no evidence that head trauma is a risk factor for these disorders. However, these latter results are based on smaller total case numbers.

Maintenance of high autopsy rates is associated with specific benefits, especially for clinical practice and for clinical and epidemiologic research. We have compiled and evaluated (on the basis of related costs and benefits) a comprehensive list of recommendations to resurrect the autopsy and reestablish it as a central contributor to medical practice, teaching, and research.

In this study, for the first time to our knowledge all new cases of Alzheimer's disease and other dementing illnesses have been documented in a well-defined United States community. A total of 178 patients in an average annual at-risk population of 18,991 persons over age 29 developed dementia during 1960 through 1964 in Rochester, Minnesota, yielding an average annual incidence rate of 187.5 new cases/100,000/year. The corresponding rate for clinically and/or pathologically diagnosed Alzheimer's disease (the most common cause of dementia in this community) was 123.3 new cases/100,000/year, based on 117 cases. The incidence rates for both dementia in general and Alzheimer's disease in particular rise dramatically with age. All patients were followed to death or to 1982, and the median survival was 63 months. These data include only those in the community who came to medical attention, but they yield higher rates than studies in Scandinavia, indicating a relatively high level of case ascertainment.

We ascertained the incidence of dementias of all causes between 1960 and 1975 among citizens of Rochester, Minnesota. Study of all medical records yielded incidence rates for the quinquennial periods of 1960-1964, 1965-1969, and 1970-1974. In the population at risk (30 years or older), the age-adjusted rates (per 100,000 population/year) for Alzheimer's disease (clinically diagnosed or pathologically confirmed, or both) in the three periods were: 104.9, 80.8, and 96.6. The rates for dementia of all causes were: 160.6, 122.0, and 136.8. Calculation of 95% confidence intervals showed that the incidence rate for dementia or Alzheimer's disease has not changed in this 15-year period in Rochester, Minnesota. Assuming no demented patients younger than 29 years, the incidence rates in the three quinquennial periods for all dements were 79.4, 60.3, and 67.7; for Alzheimer's disease they were 51.9, 40.0, and 47.8.

The clinical records and autopsy protocols were studied from 350 cases in which an autopsy was done in Olmsted County, MN, in 1980 and 1981. Overall autopsy rate was 33.6%, and autopsy rate for those aged 60 years or more was 29%. Preselected criteria were used for diagnosis of dementia. Thirty-two demented and 68 nondemented patients had complete autopsies; all were more than 60 years old. Twenty-three of 32 (72%) demented patients had Alzheimer's disease. The frequency of cerebral infarcts among the nondemented patients was significantly higher than among the demented patients (p = 0.02).

In this study, we examined in detail the patterns of autopsy rates for a half century (1935 through 1985) among residents of Olmsted County, Minnesota. The time trend of the autopsy in this community represents, in many respects, a microcosm of national trends. In the process of this analysis, we identified several medical and socioeconomic variables that may influence the rate of autopsy, including the age at death, physical location of death, gender, surgical procedures preceding death, immediate cause of death, and direct and indirect costs of the autopsy. In particular, the advancing mean age at death and the increase of the nursing home as a social phenomenon seem to have had a profound effect on autopsy rates both in Olmsted County and throughout the United States.