Risk factors for clinically diagnosed Alzheimer's disease: a case-control study of an Italian population

Hormone replacement therapy and Alzheimer's disease

There is ample evidence to show the beneficial effect of estrogen on the risk and course of Alzheimer's disease (AD). Estrogen may play a role in the pathophysiology of AD through improvement of cerebral blood flow, stimulation of the neuron or gliacyte and interaction with genetic factors. Most etiological studies of estrogen replacement therapy and AD have been retrospective studies. In these studies, the history of estrogen use was obtained from an informant, limiting the validity of the findings. Of the three follow-up studies conducted to date, one has failed to show a protective effect. There is some evidence for a synergistic effect between estrogen and the genetic factors involved in AD. However, up until now, studies of estrogen replacement therapy have generally been too small and of low validity. Large scale, long-term population studies may clarify the role of estrogen replacement therapy in the prevention and therapy of AD.

Risk of Alzheimer's disease in relatives of Parkinson's disease patients with and without dementia

OBJECTIVE

To determine whether first-degree relatives of PD patients with dementia were at increased risk for the development of AD compared with first-degree relatives of nondemented PD patients and nondemented normal subjects from the community.

METHODS

A structured family history interview was administered to 146 nondemented PD patients, 120 patients with PD and dementia, and 903 normal subjects from the community to ascertain the presence of AD among parents and siblings of these subjects. Cox proportional hazards models with double censoring techniques for missing information were used to model the risk of AD among relatives.

RESULTS

No increase in risk of AD was found among parents of patients with PD and dementia or parents of nondemented PD patients compared with parents of normal subjects. However, siblings of demented PD patients were three times as likely (relative risk [RR] = 3.2, 95% confidence interval [CI] = 1.1 to 9.4, p < 0.04) as siblings of normal subjects to develop AD. When only siblings >65 years of age were considered, there was a fivefold increase in risk of AD among siblings of demented PD patients compared with siblings of normal subjects (RR = 4.9, 95% CI = 1.1 to 21.4, p < 0.03). The risk of AD was also increased for female relatives, regardless of whether the woman was a relative of a demented PD patient, a nondemented PD patient, or a normal subject. Ethnicity and APOE genotype did not affect dementia status among relatives.

CONCLUSIONS

The increased risk of AD in siblings of demented PD patients compared with siblings of normal subjects supports the possibility of familial aggregation of AD and PD with dementia.

1998 Curt P. Richter Award. The effect of hormone replacement therapy on cognitive function in elderly women

Although evidence seems to indicate favorable effects of hormone replacement therapy (HRT) on cognitive functions and mood in elderly healthy and demented women, some questions remain. For instance, the nature of the long term effect of HRT, e.g. in preventing cognitive decline is still unclear. In this respect, the addition of progestagens in combined HRT has been mentioned to oppose some of the beneficial effects of estrogens. The present paper aims to illuminate these questions and presents two studies. In the first study, the long term effects of combined HRT in healthy postmenopausal women was investigated using a parallel groups (HRT-users vs. controls) design. HRT subjects were always tested during the estrogen-progestagen phase. Results indicated that after 6 and 12 months, women in the HRT-treatment group had higher scores on several indicators of the subjective feeling of well being (sleep, physical and psychological complaints) than matched controls, although at baseline both groups were not severely impaired. Effects of HRT on memory functions were seen when HRT treated subjects were compared with their own baseline functioning, but not when compared with controls. Hence, the addition of progestagen did not oppose the effects of estrogens on subjective feelings of well being or on memory. Our second (case-control) study involved women of middle-age who were unaware of the purpose of the experiment. No positive effects of HRT use on subjective scales of well being or on memory were found. However, women with HRT were faster on basic sensorimotor speed tasks as compared with controls. It should be kept in mind that double blind testing in an experimental study is difficult due to withdrawal bleeding and the reduction of flushes. Expectancy effects may have confounded the results of the first study. However, our findings indicate that the use of a particular design and type of memory test can explain the controversial results of studies into the effect of HRT on cognitive function. Furthermore, it was concluded that HRT has a global activating, instead of specific direct effect on cognitive functions.

Nonsteroidal anti-inflammatory drug use and Alzheimer's disease: a case-control study in Rochester, Minnesota, 1980 through 1984

OBJECTIVE

To compare the frequency of use of nonsteroidal anti-inflammatory drugs (NSAIDs) among 302 incident cases of Alzheimer's disease (AD) and age- and sex-matched control subjects.

DESIGN

We undertook a retrospective case-control study, using the resources of the Rochester Epidemiology Project.

MATERIAL AND METHODS

In ongoing studies of dementia in Rochester, Minnesota, we identified all incident cases of AD with onset between 1980 and 1984. From among all Rochester residents who received care at Mayo Clinic Rochester during those years, we selected one age- (within 3 years) and sex-matched control subject. For this study, exposure to a prescription NSAID was defined as prescribed use for 7 or more days during the 2-year window of time encompassing the year of onset and the year before onset among cases and the corresponding index year and the year prior for control subjects.

RESULTS

The odds ratio (OR) for exposure, as described, to a prescription NSAID versus no exposure to any NSAID was 0.79 (95% confidence interval [CI], 0.45 to 1.38); the OR was 1.00 (95% CI, 0.52 to 1.92) for women and 0.40 (95% CI, 0.13 to 1.29) for men. Similarly, the overall OR for aspirin exposure versus no NSAID exposure was 0.90 (95% CI, 0.54 to 1.50).

CONCLUSION

These data are suggestive but not confirmatory of a protective effect of NSAIDs for AD.

Premorbid psychosocial behavior in demented patients

We investigated the premorbid behavioral characters of demented patients in terms of life style, type A behavior, life events and coping behavior. We adopted the case control study. Significant differences were not found in the inventory scores of life style, passive coping behavior and type A behavior between dementia group and normal controls. However, the life events occurred significantly frequent in the vascular dementia group and the score of positive coping behavior was significantly low in dementia group. The results suggest that those life events and positive coping behavior might be related to the onset of dementia.

The Dorothy Russell Memorial Lecture. The molecular and cellular sequelae of experimental traumatic brain injury: pathogenetic mechanisms

The mechanisms underlying secondary or delayed cell death following traumatic brain injury (TBI) are poorly understood. Recent evidence from experimental models of TBI suggest that diffuse and widespread neuronal damage and loss is progressive and prolonged for months to years after the initial insult in selectively vulnerable regions of the cortex, hippocampus, thalamus, striatum, and subcortical nuclei. The development of new neuropathological and molecular techniques has generated new insights into the cellular and molecular sequelae of brain trauma. This paper will review the literature suggesting that alterations in intracellular calcium with resulting changes in gene expression, activation of reactive oxygen species (ROS), activation of intracellular proteases (calpains), expression of neurotrophic factors, and activation of cell death genes (apoptosis) may play a role in mediating delayed cell death after trauma. Recent data suggesting that TBI should be considered as both an inflammatory and/or a neurodegenerative disease is also presented. Further research concerning the complex molecular and neuropathological cascades following brain trauma should be conducted, as novel therapeutic strategies continue to be developed.

Cerebrospinal fluid carnitine levels in patients with Alzheimer's disease

We assessed free carnitine (FC) and acylcarnitine esters (AC) in both cerebrospinal fluid (CSF) and plasma from 24 patients with diagnostic criteria for Alzheimer's disease (AD), and from 28 healthy matched-controls. We found no significant correlation between FC and AC levels in CSF. FC and AC levels in CSF did not differ significantly between AD patients and controls, but plasma FC levels were significantly lower in AD patients. CSF and plasma FC and AC levels did not correlate with age, age at onset of AD, duration of AD, and scores of the Minimental State Examination of Folstein. Although these results suggest that CSF carnitine levels are apparently unrelated with the risk for AD, the trend of the FC/AC ratio to be higher in AD patients might suggest the possibility of a lower carnitine acetyltransferase activity in AD, as previously reported in some brain areas.

Cerebrospinal fluid levels of alpha-tocopherol (vitamin E) in Alzheimer's disease

We compared CSF and serum levels, and the CST/serum ratio of alpha-tocopherol (vitamin E), measured by HPLC, in 44 apparently well-nourished patients with Alzheimer's disease (AD) and 37 matched controls. CSF and serum vitamin E levels were correlated, both in AD patients and in controls. The mean CSF and serum vitamin E levels were significantly lower in AD patients, and the CSF/serum ratio of AD patients did not differ significantly between the 2 study groups. CSF vitamin E levels did not correlate with age, age at onset, duration of the disease and score of the Minimental State Examination in the AD group. Weight and body mass index were significantly lower in AD patients than in controls. These results suggest that low CSF and serum vitamin E concentrations in AD patients could be related with a deficiency of dietary intake of vitamin E.

Alzheimer's disease risk factors as related to cerebral blood flow: additional evidence

In a previous report, Alzheimer's disease risk factors, including alcohol abuse, depression, Down's syndrome, cerebral glucose metabolism defect, head trauma, old age, Parkinson's disease, sleep disturbance, and underactivity, were shown to have an association with reduced cerebral blood flow. In this report an attempt is made to strengthen a hypothesis that reduced cerebral blood flow may be a required cofactor in the cause of Alzheimer's disease with examples of additional putative risks, including aluminum, ApoE 4 alleles, estrogen deficiency, family history of dementia, low education-attainment, olfactory deficit, and underactivity coupled with gender, considered to have a relationship or potential relationship with reduced cerebral blood flow. Factors, believed to ameliorate Alzheimer's disease, associated with improved or stabilized cerebral blood flow are tabulated. A tentative cerebral blood flow nomogram is shown as a potential model to possibly help predict Alzheimer's disease susceptibility.

Estrogen, cognition, and a woman's risk of Alzheimer's disease

Alzheimer's disease affects women more often than men, and women with this form of dementia show greater naming (semantic memory) deficits during the course of their illness. Gonadal steroids exert organizational and activational effects on central nervous system neurons and influence brain function in other important ways. Several estrogenic actions are potentially relevant to Alzheimer's disease, and it is hypothesized that one consequence of estrogen deprivation after the menopause is a higher risk of this dementing disorder. In healthy women without dementia, estrogen may enhance cognitive performance, especially in the domain of verbal memory, although the magnitude of such effects is small. Several small treatment trials of estrogen replacement in women with Alzheimer's disease, however, suggest that estrogen's effects on cognition could be larger in this population and may be most apparent on tasks of semantic memory. Analyses in voluntary cohorts associate postmenopausal estrogen replacement therapy with a lower risk of subsequent Alzheimer's disease. In 3 recent epidemiologic studies, information on postmenopausal estrogen use was collected prospectively; while inconclusive, findings raise the possibility that postmenopausal estrogen replacement reduces a woman's risk of subsequent dementia. New information from basic research and from large randomized treatment studies, cohort studies, and case-control studies is needed to resolve important unanswered clinical issues.

Role of oestrogen in the treatment and prevention of Alzheimer’s disease

Alzheimer's disease (AD), the most common primary dementing disorder, results in devastating clinical and socio-economic consequences, and is a leading cause of death among the elderly. Despite recent advances in the neurobiology of AD, identification of effective treatment strategies has remained frustratingly elusive. Administration of currently available cholinergic drugs improves symptoms in some patients with AD, but may be associated with efficacy-limiting adverse effects. Moreover, it is not yet known whether cholinergic drugs have the potential to alter the progression of AD pathology. In contrast, cumulative evidence from basic neuroscience and clinical research demonstrates that oestrogen has significant neuromodulatory and neuroprotective properties. Furthermore, preliminary evidence from clinical studies indicates that oestrogen replacement therapy can significantly enhance cognitive function in postmenopausal women with AD, and reduce the risk for developing the disease. However, long-term administration of oestrogen is associated with potentially serious adverse effects, including increased risk for developing malignancies of the uterus and the breast. Fortunately, tissue-specific analogues of oestrogen are in development that could specifically target the functions of the brain, and may be devoid of the cancer-inducing and feminising properties of the hormone. Availability of these analogues will make it feasible to treat AD with oestrogen in both women and men. However, findings of preliminary studies, although promising, need to be confirmed in larger, controlled clinical trials before the role of oestrogen in the treatment and prevention of AD can be firmly established.

Can estrogens prevent neurodegeneration?

Estrogen replacement therapy appears to have significant beneficial effects on cognition and mood in the elderly. In recent studies, its use has been associated with short term symptomatic cognitive improvement and with a decreased risk of (or a delay in) developing Alzheimer's disease (AD). Clinical reports are supported by substantial basic scientific evidence of the neuroprotective effects of estrogens. Their specific effects on dementia and cognitive impairment remain to be delineated. Ongoing randomised trials in AD will only provide information on the symptomatic effects of estrogen. Although basic research will progress, there is currently sufficient knowledge to promote active clinical research on the possible disease-modifying or neuroprotective effects of estrogens in the elderly.

Menopause and the brain

Estrogen may have a beneficial effect on the risk and course of Alzheimer's disease (AD) through several mechanisms, including improvement of cerebral blood flow, stimulation of the neuron, or gliacyte and interaction with genetic factors. In this paper, the therapeutic and etiologic research of the role of estrogen in cognitive function and dementia is reviewed. Findings to date are promising but far from conclusive. In therapeutic research, interpretation of studies is hampered by the small sizes of the studies and differences in methodology. Most etiological studies have been limited to retrospective studies in which the history of estrogen use was obtained from an informant. Follow-up studies conducted to date have yielded controversial results. Further research is needed to elucidate the role of estrogen in the pathogenesis and progression of dementia. Subjects genetically susceptible for AD may prove to be an important high-risk group to target in preventive, therapeutic and etiologic research.

Questionable dementia: clinical course and predictors of outcome

OBJECTIVE

To evaluate the clinical course and predictors of outcome in outpatients with cognitive impairment who do not meet criteria for dementia at initial evaluation.

DESIGN

Naturalistic longitudinal study.

METHODS

Cognitively impaired patients in a memory disorders clinic who fell between the "normal" and "dementia" categories were defined broadly as "questionable dementia" (QD). Of 127 consecutive QD patients, 75 were followed for a minimum of 1 year (mean 2.5 years, SD 1.7). Baseline neuropsychological testing was conducted in 62 of these 75 QD patients.

RESULTS

At the final follow-up time-point, 41.3% met diagnostic criteria for dementia (27 of 31 patients with dementia had possible or probable Alzheimer's Disease, AD), 44% were rated as not demented, and 14.7% remained as "uncertain" dementia. Increased age was associated with the final diagnosis of dementia, but duration of follow-up, Clinical Dementia Rating, and modified Mini Mental State (mMMS) scores were not predictive. Low scores on the mMMS delayed recall subtest, consistent long-term retrieval on the Selective Reminding Test, category naming for animals, and the WAIS-R digit symbol, picture arrangement, and block design subtests were predictive of the final diagnosis of dementia (all P < or = .01). mMMS delayed recall showed 66.7% sensitivity and 71.4% specificity, the other five neuropsychological subtests together showed 66.7% sensitivity and 66.7% specificity, and the six tests together showed 81% sensitivity and 76.9% specificity. Similar predictive accuracy was obtained for the final diagnosis of AD.

CONCLUSIONS

In QD patients, poor performance on the mMMS delayed recall item may be a useful predictor of the diagnosis of dementia (and AD) on follow-up. Combining a screening instrument like the mMMS with specific neuropsychological tests may provide good predictive accuracy. In QD patients, the observed heterogeneity in diagnostic outcome, with most patients in the "dementia" and "no dementia" categories at follow-up, enhances the feasibility of evaluating early markers with predictive accuracy for dementia and AD.

The genetics of dementia in late life

Recent advances in the genetics of AD and other late-life dementias have provided new insights but also have raised new queries and ethical issues. This review reflects the current state of knowledge in a rapidly evolving field. The complex relation of genes and environment to AD, VaD, and other late-life dementias suggests that the answers to these many issues will evolve through time. New issues undoubtedly will arise as additional genes are discovered and new data accrue that relate APOE and other genes to the mechanism and expression of dementing illness. The clinical relevance and applicability of such research findings will increase when effective treatments become available. Given this potential, we encourage readers to monitor new developments as they arise.

Cerebrospinal fluid nitrate levels in patients with Alzheimer's disease

It has been suggested that nitric oxide could be implicated in the pathogenesis of Alzheimer's disease (AD). Recently Kuiper et al. reported decreased CSF nitrate levels (oxidation product that provides an indirect estimation of nitric oxide) in AD patients, assessed with a colorimetric method. However other group, using a microplate version of the Griess reaction, did not confirm these findings. We studied the CSF and plasma levels of nitrate with kinetic cadmium-reduction method in 32 AD patients and 36 matched controls. The CSF and plasma nitrate levels did not differ significantly between the two study groups. CSF and plasma nitrate levels did not correlate with age at onset and duration in the patient group. These data suggest that CSF and plasma levels of nitrate are apparently unrelated with the risk for AD.

Association between dementia and elevated TSH: a community-based study

We report on 194 individuals (96 men and 98 women), aged 65 and over, who had dementia assessments and basal TSH measurements as part of an ongoing epidemiological study of dementing disorders in a larger population. Dementia was diagnosed according to DSM-III-R and measured by the Clinical Dementia Rating scale; CDR scores of 0, 0.5, and > or = 1, represent individuals with no dementia (n = 122), possible dementia (n = 29), and definite dementia (n = 43), respectively. The odds ratio for the association of elevated TSH with definite dementia (CDR > or = 1) was 3.8 (95% confidence interval = 1.6, 9.1) and with possible and/or definite dementia (CDR > or = 0.5) was 3.8 (95% confidence interval = 1.6, 9.2), after adjusting for the effects of age, gender, and level of education. This is the first community-based study to report an association between TSH elevation and dementia. Our findings are consistent with recent evidence that subclinical hypothyroidism is associated with cognitive impairment, and that thyroidal state may influence cerebral metabolism.

Recent advances in the genetics of Alzheimer's disease and vascular dementia with an emphasis on gene-environment interactions

OBJECTIVE

To review recent findings in the genetics of Alzheimer's disease (AD) and vascular dementia (VaD) with particular emphasis on gene-environment interactions.

DESIGN

A survey and critique of recent literature on the genetic etiology of AD and VaD.

CONCLUSIONS

Recent research has identified several genes associated with AD, including loci on chromosome 1, 14, 19, and 21. Two of these loci, encoding the beta-amyloid precursor protein and apolipoprotein E, have gene products that are well characterized and of evident significance in the pathogenesis of AD. The four genes together probably account for little more than 50% of all cases of AD, but other undiscovered loci are likely. Interaction of genetic effects with environmental influences may affect both onset and expression of AD. By contrast, only a small minority of VaD cases can be attributed to a pure genetic etiology. The majority of VaD is caused by both genetic and environmental factors. Many of the environmental antecedents also have genetic determinants (e.g., smoking). Knowledge of the gene-environment interactions for both AD and VaD will facilitate identification of early preclinical symptoms of disease, a stage of the disease process during which treatment may be most beneficial.

The effects of hormone replacement therapy, lipoprotein cholesterol levels, and other factors on a clock drawing task in older women

OBJECTIVES

To assess the associations of a clock drawing task with hormone replacement therapy and other factors in older women.

DESIGN

Group comparisons.

SETTING

Leisure World Laguna Hills, retirement community in southern California.

PARTICIPANTS

Two hundred ninety-two postmenopausal women who were analyzed for lipoprotein levels in 1987-88 were contacted by postal survey, which included a clock drawing task, in 1992; 168 women who drew normal clocks were compared with 46 who drew abnormal or blank clocks.

MEASUREMENTS

Clock drawings; lipoprotein cholesterol levels; serum progesterone, estrone, estradiol, and steroid hormone binding globin levels; self-reported data on smoking, alcohol intake, prior medical diagnoses, and use of certain medications including hormone replacement therapy and analgesics.

RESULTS

Women with normal clocks had significantly lower total cholesterol (P = .01), LDL cholesterol (P = .03), and serum progesterone levels (P = .03). They weighed, on average, 5 more pounds at the time of last menstrual period (P = .05), were more likely to use combined hormonal replacement therapy (P = .06), and were less likely to use acetaminophen daily (P = .02) than women with abnormal clocks. Serum estrone and estradiol levels did not differ significantly between women with normal and abnormal clocks.

CONCLUSION

The associations found here suggest that high serum cholesterol and progesterone levels might have a negative effect on clock drawing performance. Acetaminophen may also be related to worse performance on this task.

An epidemiological study of dementia in a rural community in Kerala, India

BACKGROUND

This community-based epidemiologic study of dementia in a rural population in India investigated the prevalence of various dementing disorders in the community, psychosocial correlates of the morbidity, and assessment of the risk factors associated with dementia.

METHOD

A door to door survey was conducted to identify elderly people aged 60 and above. A total of 2067 elderly persons were then screened with a vernacular adaptation of the MMSE. All those who scored 23 and below had a detailed neuropsychological evaluation by CAMDEX-Section B, and the care-givers of the people with confirmed cognitive impairment were interviewed using CAMDEX-Section H to confirm the history of deterioration or impairment in social or personal functioning. In the third phase the subjects with confirmed cognitive impairment were evaluated at home as to whether they satisfied the DSM-III-R criteria for dementia. Subcategorisation of dementia was done based on ICD-10 diagnostic criteria. Five percent of those whose screening was negative were randomly selected and evaluated during each stage.

RESULTS

Sixty-six cases of dementia were identified from 2067 persons aged 60 and above, a prevalence rate of 31.9 per thousand. After correction this rate was 33.9 per thousand. Fifty-eight percent of the dementia cases were diagnosed as vascular dementia and 41% satisfied the criteria for ICD-10 dementia in Alzheimer's disease. There were more women in the Alzheimer's disease group; smoking and hypertension were associated with vascular dementia while a family history of dementia was more likely in the Alzheimer's group.

CONCLUSION

Dementia is an important cause of morbidity in the geriatric population in this community, where families take responsibility for the care of relatives with dementia.

The clinical epidemiology of Alzheimer's disease

Alzheimer's disease is a more common and malignant illness than was appreciated just 2 decades ago. In addition to being a major cause of mortality, it is costly and uniquely distressing for patients and their families. All indications are that the problem will grow as elderly populations expand. Fatalism regarding AD is premature, however. Much has been learned about this disease in only a few years, and it is hoped that this rate of discovery can be maintained or even accelerated in the future.

Beta AP deposition and head trauma

Head trauma is considered to be a risk factor for Alzheimer's disease, because a high prevalence of beta AP deposits has repeatedly been reported in patients who died within a few days following head injury. To evaluate this statement, we undertook two studies using immunohistochemistry for beta AP and found a surprisingly low prevalence of beta AP diffuse deposits. We first selected 23 patients aged 17-63 years, who died 0-76 days after head trauma. Using beta AP antibody at the usual dilution (1:100), we did not find any deposits. With a high concentration of antibody (dilution 1:2) we found beta AP diffuse deposits in one 46-year-old case. In a second study, 17 patients aged 60-79 years old, who died 1-35 days after head injury, were compared to a control group. We did not find any significant difference in the density of beta AP diffuse deposits between cases and controls using usual dilutions of beta AP antibody. The density of beta AP diffuse deposits was linked only to aging and the presence of senile plaques.

Alzheimer's disease risk factors as related to cerebral blood flow

Inconsistencies within results of case-control studies on Alzheimer's disease risk factors led to a search of the literature for a potential cofactor. Reduced cerebral blood flow was selected and literature was surveyed for evidence of a cerebral blood flow linkage with the more than 40 putative risks. Alcohol abuse, depression, head trauma, underactivity, old age, sleep disturbance, glucose utilization, Down's syndrome, and Parkinson's disease are risk factors where an association with reduced cerebral blood flow is documented. Studies were cited showing that improved cerebral blood flow is associated with factors thought to be helpful in Alzheimer's disease, such as education or occupational attainment, exercise, headache, smoking, and arthritis/anti-inflammatory drugs to the extent that aspirin is used. Sugar consumption is identified as a potential risk factor with glucose management in Alzheimer's disease also shown to involve reduced cerebral blood flow. An hypothesis is developed showing how compromised regional cerebral blood flow could fit as a cofactor for genetic, autoimmune, and neurotoxic aspects of Alzheimer's disease.

A case-control study of Alzheimer's disease and aluminium occupation

BACKGROUND

We examined clinically diagnosed Alzheimer's disease patients and controls, and collected information from informants, to examine the association between Alzheimer's disease and aluminium occupation.

METHOD

An unmatched case-control study comparing 198 cases of Alzheimer's disease (ADRDA-NINCDS diagnostic criteria), to selected controls (164 other dementias and 176 nondementing group) in respect of their occupational history. The subjects included all patients referred to and seen by the first author during a 2 year study period.

RESULTS

Twenty-two of 198 patients with Alzheimer's disease (11.1%) reported having an aluminium occupation at some stage in their working life compared with 39 of 340 controls (11.5%), odds ratio 0.98, 95% Cl 0.53-1.75, P > 0.05. Aluminium workers reported to have worked in direct contact with aluminium dust and fumes did not appear to be at any greater risk than other workers who were employed at the same factory, odds ratio 1.19, 95% Cl, 0.64-4.18, P > 0.05.

CONCLUSION

There is no evidence to support an association between having previously worked in an aluminium factory and the risk of Alzheimer's disease later in life.

Estimation of the proportion of genetic cases in late-onset diseases: an application to Alzheimer's disease

In diseases with a complex etiology including a genetic component, an important issue is to determine the proportion of cases really having inherited the disease. This is not easy in late-onset diseases where censoring might obscure the transmission pattern of the disease and give an apparently non-genetic distribution of the cases. We present a model that allows the estimation of the proportion of genetic cases in late-onset diseases. This model takes censoring into account by explicit modelling of the time dependency of the onset of the disease. The model is illustrated with an example based on an epidemiological survey in Alzheimer's disease and with simulated data.

Characteristics of familial aggregation in early-onset Alzheimer's disease: evidence of subgroups

Characteristics of familial aggregation of Alzheimer's Disease were studied in 92 families ascertained through a clinically diagnosed proband with an onset below age 60 years. In each family data were systematically collected on the sibships of the proband, of his father, and of his mother. A total of 926 relatives were included and 81% of the living relatives (i.e., 251 individuals) were directly examined. The estimated cumulative risk among first degree relatives was equal to 35% by age 89 years (95% confidence interval 22 to 47%). This result does not support the hypothesis that an autosomal dominant gene, fully penetrant by age 90 years, is segregating within all these pedigrees. Despite the fact that all probands were selected for an onset before age 60 years it was shown that two types of families could be delineated with respect to age at onset among affected relatives: all secondary cases with an onset below age 60 years were contributed by a particular group of families (type 1 families), whereas all secondary cases with an onset after age 60 years were contributed by another group of families (type 2 families). Although genetic interpretation of these findings is not straightforward, they support the hypothesis of etiologic heterogeneity in the determination of early-onset Alzheimer's disease.

Head injury as a risk factor in Alzheimer's disease

Several case-control studies have reported head injury to be more common among patients with Alzheimer's disease (AD) than healthy elderly controls. The present study sought to determine whether milder head injury is also a risk factor for AD. Furthermore, it was hypothesized that head injury would be more common among AD patients without a genetic risk for the disease. History of head injury in 68 consecutive cases of probable or definite AD and 34 non-demented control subjects was ascertained from their spouses. Head injury was reported in 20 of the AD patients (29%), and in only one control subject (2.9%) (odds ratio = 13.75). Twenty per cent of the familial and 43.5% of the sporadic AD cases reportedly had a premorbid head injury (odds ratio = 3.08). Head injury had no effect on age of dementia onset. The results indicate that head trauma may be a predisposing factor to AD, particularly in the absence of a clear genetic contribution.

Life events and senile dementia. I. Admission, deterioration and social environment change

This study examines the frequency of life events before admission and before deterioration in 70 dementia patients, in comparison with 50 dementia controls living in the community and 50 fit elderly people matched for age and sex. We hypothesized that there would be an excess of events connoting changes in routine and the social environment. Specific scales were developed to measure these aspects of events. Our results supported the initial hypothesis, confirming that it is the social disruptiveness of change rather than the threat implied by life events that is associated with deterioration. The findings are discussed in the light of current models of the dementia process.

Increased risk of Alzheimer's disease in mothers of adults with Down's syndrome

Most adults with Down's syndrome (DS) develop neuropathology characteristic of Alzheimer's disease (AD) by the age of 40. Most of the non-dysjunction events in DS are of maternal origin. We postulated therefore that a shared genetic susceptibility to DS and AD would be associated with an increased frequency of AD among mothers, but not fathers, of individuals with DS. We further hypothesised that the shared susceptibility could involve an accelerated ageing process, leading to the birth of a child with DS to a relatively young mother and to an increased risk of dementia in the mother and her relatives. Families of 96 adults with DS and of 80 adults with other forms of mental retardation were ascertained through the New York State Developmental Disabilities services network. A semi-structured interview was used to obtain information on the presence or absence of non-stroke-related dementia and other disorders in parents. There was an increase in risk of dementia among mothers of DS probands compared with control mothers (risk ratio 2.6 [95% CI 0.9-7.3]). The risk of dementia among mothers who were 35 or younger when their DS children were born was 5 times that of control mothers (4.9 [1.6-15.4]). There was no increase in risk of dementia among mothers who were older (> 35 years) at the proband's birth (0.8 [0.2-3.4]). There was no difference in risk of dementia between fathers of DS cases and fathers of controls (1.2 [0.4-3.9]) and no discernible influence of age on this risk. Familial aggregation of dementia among mothers of adults with DS supports the hypothesis of a shared genetic susceptibility to DS and AD.

Involvement of free oxygen radicals in beta-amyloidosis: an hypothesis

Compelling evidence suggests that cerebral deposition of aggregating beta-amyloid protein may trigger the neurodegenerative cascades of Alzheimer's disease, Down syndrome, and, to a lesser degree, normal aging. We propose further that free oxygen radicals are critically involved in beta-amyloidosis. Apart from the established role of free radicals in other amyloidoses, our proposal is consistent with a large number of findings. Among these are (a) the salient relationship of Alzheimer's disease with aging and the increase in free oxygen radical liberation with advancing age; (b) biochemical and analytic epidemiologic evidence that free radical formation is increased in the disorder; (c) preliminary evidence that quenching free radicals slows the clinical progression of Alzheimer's disease; (d) the early and invariable beta-amyloid accumulation in trisomy 21, a syndrome associated with elevated free radical activity and with concomitant high levels of beta-amyloid precursor protein; (e) other factors that may be associated with increased liberation of free oxygen radicals and deposition of beta-amyloid protein. Possible mechanisms by which free radicals might modulate beta-amyloidosis are discussed.

Copper-zinc superoxide dismutase activity in red blood cells in probable Alzheimer's patients and their first-degree relatives

The activity of the enzyme copper-zinc superoxide dismutase (Cu-Zn SOD) has been investigated in red blood cell (RBC) homogenate obtained from demented patients with probable Alzheimer's disease (DAT), from their first-degree relatives (sisters/brothers and sons/daughters), and from healthy control families of the same age. A statistically significant increase in SOD activity (P < 0.01) was found in RBC's homogenate between families of DAT patients (not including the demented individual) and control families. Variability in SOD activity due to differences between families was not significant for DAT relatives; a significant variance component (P < 0.05) was found between control families. Additionally, a statistically significant increase in SOD activity (P < 0.001) with age in DAT patients up to 70 years and a significant decrease above this age were found, confirming a previously found relation. No changes in SOD activity with age were detected in healthy controls nor in DAT relatives. The increased levels of Cu-Zn SOD, probably represent a general alteration of the oxidative processes characteristic of this dementia and support the proposal that the enzyme could be used as an early diagnostic peripheral marker of the Alzheimer's disease (AD), and to determine to which subgroup the patient belongs, as well as a risk factor in non-demented first-degree relatives.

Beta amyloid protein deposition in the brain after severe head injury: implications for the pathogenesis of Alzheimer's disease

In a recent preliminary study it was reported that a severe head injury resulted in the deposition of beta amyloid protein (beta AP) in the cortical ribbon of 30% of patients who survived for less than two weeks. Multiple cortical areas have now been examined from 152 patients (age range 8 weeks-81 years) after a severe head injury with a survival time of between four hours and 2.5 years. This series was compared with a group of 44 neurologically normal controls (age range 51 to 80 years). Immunostaining with an antibody to beta AP confirmed the original findings that 30% of cases of head injury have beta AP deposits in one or more cortical areas. Increasing age seemed to accentuate the extent of beta AP deposition and potential correlations with other pathological changes associated with head injury were also investigated. In addition, beta amyloid precursor protein (beta APP) immunoreactivity was increased in the perikarya of neurons in the vicinity of beta AP deposits. The data from this study support proposals that increased expression of beta APP is part of an acute phase response to neuronal injury in the human brain, that extensive overexpression of beta APP can lead to deposition of beta AP and the initiation of an Alzheimer disease-type process within days, and that head injury may be an important aetiological factor in Alzheimer's disease.

Alzheimer's disease and cumulative exposure to anesthesia: a case-control study

OBJECTIVE

To evaluate prior exposure to general anesthesia as a potential risk factor for Alzheimer's disease (AD).

DESIGN

A retrospective, population-based, case-control study.

SETTING

The Rochester Epidemiology Resource.

PATIENTS

Cases were all incident cases of AD from 1975 to 1984 who resided for 40 years or more in Olmsted County prior to the onset of their 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. The case and control groups each had 252 individuals. Of these, 208 cases and 199 controls had at least one exposure to general anesthesia prior to the year of onset of dementia in the matched AD patient.

MEASUREMENTS

The cumulative duration of anesthesia and the total number of general anesthetic exposures prior to the age of onset of dementia and the corresponding year in each matched control were ascertained.

RESULTS

There was no significant difference in mean cumulative exposure (in minutes) to general anesthesia (patients vs controls: 188.4 vs 170.5 minutes, ns). Neither exposure to six or more episodes of general anesthesia (OR = 1.44; 95% CI: 0.77-2.71) nor cumulative exposure to 600 minutes or more of general anesthesia (OR = 1.63; 95% CI: 0.53-5.04) were associated with a significantly increased risk of AD.

CONCLUSION

It is unlikely that multiple exposures to general anesthesia increase the risk of AD.

A comparison of multiplex and simplex families with Alzheimer's disease/senile dementia of Alzheimer type within a well defined population

A study was made on 150 clinically demented patients presenting at autopsy at Umeå University Hospital in Sweden. In 90 of the cases dementia was considered to be primary in nature and of these forty six per cent (41 cases), fulfilled both the clinical and histopathological criteria for the diagnosis of Alzheimer's disease/Senile dementia of Alzheimer type (AD/SDAT). The families of these 41 AD/SDAT cases were then studied, and a family history obtained through interviews with multiple family informants and from civil and medical records. Additional diseased family members suffering from progressive dementia (multiplex families) were observed in 12 probands out of 41 (29%). Multiplex families exhibited similar clinical and histopathological characteristics as simplex families containing a single affected individual. The secondary cases in the multiplex families exhibited similar demographic and clinical characteristics as the probands. 39% of the multiplex and 14% of the simplex cases had an early age of onset of the disease, that was under 65 years. The overall prevalence of progressive dementia disorders in the 41 families was 5.9%. The prevalence of a progressive dementia disorder was 11% in the multiplex families (14% for the early onset cases) and 3.5% in the simplex families (2% for the early onset cases). The prevalence of progressive dementia disorder for family members who had passed the mean age of the onset of the disease for their family, was 45% for multiplex and 18% for simplex families. Furthermore the incidence rate for dementia was significantly higher (p < 0.005) in multiplex families (5.5 per 1,000 person years) when compared to simplex families (2.5 per 1,000 person years). No differences could be seen in parental age at birth of the diseased when comparing the two sets of families. However in multiplex families the duration of the disease was significantly (p < 0.025) shorter, in subjects with parental age at birth over 35 years compared to those with a parental age under 35 years. The multiplex families contained significantly (p < 0.025) larger sibships; and showed a significantly lower age of onset for the disease (p < 0.001), and a significantly longer duration of disease (p < 0.05) compared to the simplex families. A significant intra familial correlation of age at disease onset was observed in both sets of the families.

Interaction between genetic and environmental risk factors for Alzheimer's disease: a reanalysis of case-control studies

To study the interaction among genetic and environmental risk factors, a reanalysis of case-control studies of Alzheimer's disease (AD) was conducted based on the original data of all studies carried out to January 1, 1990. Seven studies were included in the present analysis, comprising a total of 814 AD patients and 894 control subjects. When comparing those with a positive and negative family history of dementia, similar odds ratio were found for late maternal age [1.7; 95% confidence interval (0.6-4.8) vs. 2.0 (1.1-3.5)], head trauma [1.7 (0.7-4.2) vs. 1.9 (1.1-3.2)], and history of depression [2.0 (0.2-19.8) vs. 2.1 (0.8-1.7)]. This suggests a model in which these risk factors increase the risk for AD independent of family history of dementia. Among those with a positive family history of dementia, the odds ratios for family history of Down's syndrome [4.2 (0.9-20.0)] and of Parkinson's disease [3.3 (0.4-28.2)] tended to be higher than among those with a negative family history of dementia [2.6 (0.8-8.5) and 2.4 (0.8-7.0), respectively]. However, for both disorders the difference in odds ratio was not statistically significant. For history of cigarette smoking, there was no association to AD for those with no first degree relatives with dementia and an inverse relation with AD for those with a positive family history. Although in all analyses, family history of dementia remained significantly associated with AD in the absence of other factors, the odds ratio associated with family history of dementia tended to be lower for those with a positive smoking history, particularly for those with two or more affected relatives. These findings suggest that smoking may interact specifically with a genetically determined process.

Molecular genetics of Alzheimer's disease

At present it is not clear whether Alzheimer's disease is a single disease, a complex syndrome, or a heterogeneous ill-defined group of disorders. In the last few years significant progress has been made in identifying and describing its different manifestations, as well as the underlying biological mechanisms. Modern molecular biology techniques have provided new insights into possible etiological mechanisms. Linkage analysis and gene sequencing studies have produced evidence of a possible locus on chromosome 21 in a small group of families with early onset familial Alzheimer's disease (FAD). It was shown that another small group of early onset FAD families develops the disease as a result of mutations in the gene coding for the beta-amyloid precursor protein, and that in a larger subgroup of early onset families the disease appears to be caused by an unidentified gene on chromosome 14. Several other early onset FAD families are clearly not linked to any of these loci, suggesting that other abnormal genes, probably on different chromosomes, might be the cause of the disease in these families. Finally, it was recently shown that the epsilon 4 allele of apolipoprotein E (ApoE) gene, which has been mapped to chromosome 19, is associated with an increased risk of developing the disease in late onset FAD families and sporadic cases. These results not only evidence that Alzheimer's disease is a genetically heterogeneous disorder, but also delineate new approaches in the study of the etiological and pathogenetic mechanisms of Alzheimer's disease.

Symptom progression in Alzheimer's disease: relation to onset age and familial aggregation. Results of a longitudinal study

We investigated the hypotheses that symptom progression in Alzheimer's disease is related to onset age and familial aggregation. In a psychiatric outpatient clinic we examined a cohort of 265 consecutively admitted patients 90 of which were diagnosed mild to moderate Alzheimer's disease according to the ICD-10 research criteria. Within twelve months follow-up 73 cases of these 90 patients were investigated twice. We found that early onset cases compared to late onset cases as well as patients with a familial aggregation compared to patients without such an aggregation were no different with respect to the rate of symptom progression in Alzheimer's disease. Furthermore, the hypothesis that early onset cases with a familial aggregation more rapidly deteriorate cognitively compared to late onset cases without such an aggregation could not be confirmed. Our results suggest that the large interindividual variation of symptom progression in Alzheimer's disease cannot be explained by onset age and familial aggregation.

Genetic transmission of Alzheimer's disease among families in a Dutch population based study

We evaluated age at onset and transmission patterns of Alzheimer's disease (AD) in families of 198 patients who had onset of symptoms before the age of 65 years and were diagnosed before the age of 70 years. Patients were ascertained in a population based study in The Netherlands. The results suggest that the risk of AD by the age of 90 in first degree relatives is 39% (95% confidence interval 27 to 51). By the age of 90, this risk is 2.8 (95% confidence interval 1.5-5.2) times greater than the corresponding risk of 14% among relatives of age and sex matched control subjects. Segregation analysis indicated that patterns of familial clustering are best explained by transmission of a major autosomal dominant gene with reduced penetrance and a multifactorial component. However, the single major locus model could be rejected in favour of the mixed model only when a cohort effect for heritability was allowed for. The frequency of the AD susceptibility allele was estimated to be 0.48% in the single major locus model and 0.31% in the mixed model. Although our study confirms that a dominant major gene is implicated in early onset AD, the results suggest that other genetic or perhaps non-genetic factors may account for the disease in a considerable number of patients.

Oxidative polymorphism of debrisoquine is not related to the risk of Alzheimer's disease

Oxidative polymorphism of debrisoquine has been studied in patients suffering from many spontaneous disorders which show genetic and/or environmental factors in their pathogenesis. To elucidate whether any relationship exists between this genetic polymorphism and the risk of developing Alzheimer disease (AD) we determined the oxidative phenotype and metabolic ratio (MR) of debrisoquine (DBQ) in 47 patients with AD or senile dementia of Alzheimer type (SDAT) and 837 healthy controls. The patients were free of drugs during at least the previous 30 days; all the controls were free of drugs. Three patients (6.38%) and 42 controls (5.02%) were classified as poor metabolizers (PM) of DBQ (non-significant difference). The distribution of MR values in the AD/SDAT patients showed non-significant differences when compared with controls. There was no relation between oxidative polymorphism of DBQ and age at onset of the disease. These results suggest that DBQ oxidative genetic polymorphism cannot be considered as a risk factor for developing AD-SDAT.

Genetic susceptibility and head injury as risk factors for Alzheimer's disease among community-dwelling elderly persons and their first-degree relatives

We performed a community-based study to investigate the relationship of genetic susceptibility and head injury to Alzheimer's disease (AD) in 138 patients with AD and 193 healthy elderly control subjects. Data concerning presence or absence of dementia and certain exposures were also obtained from 799 first-degree relatives of the patients and 1,238 first-degree relatives of the control subjects. Adjusting for age, gender, and other risk factors, the odds ratio for AD associated with head injury was 3.7 (95% confidence interval [CI], 1.4-9.7). The association was highest for head injuries that occurred after age 70. The risk of AD was higher in first-degree relatives of patients with onset prior to age 70 than in relatives of control subjects (risk ratio [RR] = 2.5; 95% CI, 1.1-5.6). The risk was not increased for relatives of patients with onset of AD at age 70 or older. Compared with relatives without head injury, the risk of AD was increased among both head-injured relatives of patients (RR = 5.9; 95% CI, 2.3-14.8) and head-injured relatives of control subjects (RR = 6.9; 95% CI, 2.5-18.9). Our results are consistent with the hypothesis that severe head injury and genetic susceptibility are associated with AD. Both associations concur with current concepts regarding the role of amyloid in AD. Although we regard head injury, like genetic susceptibility, to be a putative risk factor for AD, the temporal relationship between head injury and AD warrants further investigation.

Cerebrospinal fluid proteins in patients with leucoaraiosis: possible abnormalities in blood-brain barrier function

Some CSF protein abnormalities have been proposed as a possible marker for vascular dementia. We studied the CSF protein levels and albumin ratio in 21 patients (mean age 64.04 +/- 7.5) with progressive bilateral motor impairment, and a CT picture of leucoaraiosis. Seven of these patients also presented with dementia. Twenty-seven Alzheimer's disease patients (mean age 59.59 +/- 5.30) without leucoaraiosis were taken as controls. We also evaluated the correlations of the albumin ratio values with the diagnosis of dementia, the severity of cognitive impairment, the degree of cerebral atrophy and presence of infarcts on CT, and the abnormalities in CSF circulation, found on isotopic cisternography, in the leucoaraiosis group. After controlling for age and sex, the patients with leucoaraiosis showed greater CSF albumin levels (0.27 g/l +/- 0.11 vs. 0.21 g/l +/- 0.06; covariance analysis P = 0.066), CSF IgG values (4.68 mg/100 ml +/- 1.45 vs. 2.85 mg/100 ml +/- 1.03; covariance analysis P < 0.001), and a higher albumin ratio (0.0078 +/- 0.0027 vs. 0.0058 +/- 0.0019; covariance analysis P = 0.013) than those with Alzheimer's disease. The variations of these parameters were not apparently related to the presence of dementia in the leucoaraiosis group. A significantly higher albumin ratio was observed in patients with a slowed CSF circulation compared to those with normal CSF circulation (0.0086 +/- 0.0028 vs. 0.0059 +/- 0.0019; covariance analysis P = 0.05). We conclude that, independently from the presence of dementia, patients with leucoaraiosis have CSF abnormalities consistent with functional blood-brain barrier alterations.

Risk factors for late-onset Alzheimer's disease: a population-based, case-control study

Our current knowledge of risk factors for Alzheimer's disease is limited and primarily addresses early-onset disease. This study aimed to determine the risk factors for late-onset Alzheimer's disease using a case-control approach. Ninety-eight cases and 216 controls were gathered from an ongoing population survey on aging and dementia in Stockholm (the Kungsholmen Project). We found a high relative risk (3.2; 95% confidence interval, 1.8-5.7) with the presence of at least one first-degree relative affected by dementia. Among all the other risk factors, alcohol abuse (relative risk, 4.4; 95% confidence interval, 1.4-13.8) and manual work (relative risk for men of 5.3; 95% confidence interval, 1.1-25.5) emerged as positively associated. No clear association was found with a family history of Parkinson disease, advanced parental age at index delivery, season of birth, or previous head trauma. In conclusion, our data suggest that the main risk factor for late-onset Alzheimer's disease is a family history of dementia, as has been previously reported for early-onset disease. Moreover, alcohol abuse and occupational exposure might play a specific role for this form of the disease.

Clinical features distinguishing large cohorts with possible AD, probable AD, and mixed dementia

OBJECTIVE

To determine whether clinical features and rate of cognitive and functional decline differed in cohorts of possible AD (poAD), probable AD (prAD), and mixed dementia (MIX) patients.

DESIGN

Cohort study with 1-year follow-up examination, comparing three groups of subjects.

SETTING

Outpatient evaluation at nine California Alzheimer's Disease Diagnostic and Treatment Centers (ADDTC).

PATIENTS

There were 1701 elderly patients who presented for evaluation of memory complaints.

MEASUREMENTS

Historical, physical, and neurological variables for cross-sectional comparisons and 1-year rate of change on the Mini-Mental State Examination (MMSE), Blessed Information-Memory-Concentration test (BIMC), and Blessed Dementia Scale (BDS).

RESULTS

Mean initial MMSE scores for poAD (n = 279), prAD (n = 928) and MIX (n = 430) were 17.9 (+/- 7.4), 13.9 (+/- 7.5), and 15.4 (+/- 7.1). Delusions and psychosis occurred in about one-third of each group, most often in those with moderate dementia (MMSE 11-20). PoAD were distinguished from prAD by significantly more alcohol abuse, physical health problems, and focal motor or sensory findings. MIX differed from AD alone by increased prevalence of cardiovascular disease, hypertension, stroke, TIA, and exposure to general anesthesia, and by a greater frequency on exam of depressed mood, focal motor or sensory findings, and gait disorder. All groups declined by about 2.8 points on the BIMC, 2.9 points on the MMSE, and 1.8 points on the BDS, a functional scale, over 1 year. Neither extrapyramidal signs nor psychosis predicted a more rapid rate of decline.

CONCLUSIONS

Various features help to distinguish poAD, prAD, and MIX in a large cohort of patients, but do not predict the rate of progression.

The Seattle Alzheimer's disease data set

Forty families submitted to Genetic Analysis Workshop 8 are described. These are the families in the Seattle data set which have been typed for at least one genetic marker from the centromeric region of chromosome 21 or the q arm of chromosome 19. Thirteen of these families have average ages of onset below age 61 and are therefore considered to be early onset families. Seven of the families are of Volga German descent. Thirty-four of the families have autopsy documented Alzheimer's disease, including all 13 of the early onset pedigrees. The data set includes both the clinical and pedigree information available on the portions of the pedigrees used in the linkage analyses, genotype data on three loci on chromosome 19 and four loci on chromosome 21, and more extended family data on individuals who have not been included in the linkage analyses.