Subtypes of sleep problems in patients with Alzheimer disease.

OBJECTIVE: Sleep disturbances are common in patients with Alzheimer disease (AD) and can contribute to cognitive dysfunction and a negative impact on patients' and caregivers' quality of life. The purpose of this study was to evaluate whether subtypes of sleep disturbance could be identified in patients with AD and to assess the relation of these subtypes to patient characteristics and caregiver mood. METHODS: As part of routine clinical assessment, primary caregivers of 344 patients with AD completed a questionnaire that included five items about the patients' sleep. Patients' cognitive and functional status and their mood were assessed as was caregivers' mood. Latent class analysis was used to define subgroups of patients based on their sleep patterns. After identification of groups of sleep disturbance, the relation of group membership to patient and caregiver characteristics was also evaluated. RESULTS: Analyses revealed groups with moderate and severe sleep problems as well as a group without problems. Patients with more severe sleep disturbance were older, less well educated, and had poorer cognitive and functional status. Caregiver and patient depression was related to membership in the severe group, suggesting that both may contribute to caregivers' ratings of more severe sleep disturbance, whereas only patient depression was related to membership in the moderate group. CONCLUSION: Sleep problems in patients with AD are related to poorer cognitive and functional status and patient and caregiver depression. Caregiver depression was most closely related to more severe patient sleep disturbance.

Caregiver reports of sleep problems in non-Hispanic white, Hispanic, and African American patients with Alzheimer dementia.

STUDY OBJECTIVES: Sleep problems are common in persons with dementing illnesses and among the most stressful patient behaviors for caregivers. Although studies have shown differences in sleep across ethnic groups, little information is available on ethnic differences among persons with dementia. The purpose of this study was to investigate possible ethnic differences in sleep problems among patients with Alzheimer dementia. METHOD: Caregiver reports of 5 sleep- or circadian rhythm-related behavioral problems (behavior disturbance worse in the evening, difficulties falling asleep, frequent awakenings, early awakenings, and excessive daytime sleep) were evaluated in 395 patients who had received a diagnosis of Alzheimer disease after diagnostic evaluation. The average cognitive score of the groups suggested that they could be characterized as having moderately severe impairment. The frequency of sleep problems was then evaluated across subgroups defined by self-reported ethnicity (African American, Hispanic, and non-Hispanic white). As patient and caregiver characteristics may affect caregivers' reports of patients' behaviors, mixed effects regression models were used to adjust for patient and caregiver variables that might affect caregiver reports. RESULTS: Analyses revealed ethnic differences in sleep or circadian rhythm disturbances. African American and Hispanic patients were reported to have more severe sleep disturbances than non-Hispanic whites. After correction for patient and caregiver variables that might have affected caregiver reports, differences between African Americans and others remained. CONCLUSIONS: Sleep problems in patients with dementing illnesses are reported by caregivers with differing frequencies across groups of African Americans, Hispanics, and non-Hispanic whites. Clinicians should be aware of these differences in assessing sleep disturbance in patients with dementia as well as the potential effects of patient and caregiver variables on reports of these problems.

Single-neuron theory of consciousness.

By most accounts, the mind arises from the integrated activity of large populations of neurons distributed across multiple brain regions. A contrasting model is presented in the present paper that places the mind/brain interface not at the whole brain level but at the level of single neurons. Specifically, it is proposed that each neuron in the nervous system is independently conscious, with conscious content corresponding to the spatial pattern of a portion of that neuron's dendritic electrical activity. For most neurons, such as those in the hypothalamus or posterior sensory cortices, the conscious activity would be assumed to be simple and unable to directly affect the organism's macroscopic conscious behavior. For a subpopulation of layer 5 pyramidal neurons in the lateral prefrontal cortices, however, an arrangement is proposed to be present such that, at any given moment: (i) the spatial pattern of electrical activity in a portion of the dendritic tree of each neuron in the subpopulation individually manifests a complexity and diversity sufficient to account for the complexity and diversity of conscious experience; (ii) the dendritic trees of the neurons in the subpopulation all contain similar spatial electrical patterns; (iii) the spatial electrical pattern in the dendritic tree of each neuron interacts non-linearly with the remaining ambient dendritic electrical activity to determine the neuron's overall axonal response; (iv) the dendritic spatial pattern is reexpressed at the population level by the spatial pattern exhibited by a synchronously firing subgroup of the conscious neurons, thereby providing a mechanism by which conscious activity at the neuronal level can influence overall behavior. The resulting scheme is one in which conscious behavior appears to be the product of a single macroscopic mind, but is actually the integrated output of a chorus of minds, each associated with a different neuron.

Prevalence of dementia in three ethnic groups: the South Florida program on aging and health.

To determine the prevalence of cognitive impairment and dementia in a multi-ethnic community, we examined a population sample of 2,759 elderly (65 years of age and older) African American, Hispanic-Cuban and white non-Hispanic men and women of Dade County, Florida. The Short Portable Mental Status Questionnaire (SPMSQ) was used as a screening test. The prevalence of cognitive impairment for African American men was 17.0% and women 16.7%; Cuban men 9.4% and women 11.4%; and white non-Hispanic men 9.0% and women 8.5%. Participants with cognitive impairment were referred to two Memory Disorder Clinics for diagnosis of dementia/Alzheimer's disease (AD). SPMSQ cutpoints took account of race and education. The prevalence of dementia/AD was adjusted for sensitivity and specificity of the SPMSQ in each sex/ethnic group. The prevalence of dementia among African American men (20.9%) was twice that among white non-Hispanic men (11.6%). White non-Hispanic and Cuban women had a similar prevalence of dementia (12.1% vs. 12.9%). Low SPMSQ specificity for Cuban men and African American women gave unstable dementia prevalence estimates. More than two thirds of all dementia cases had AD, and among white non-Hispanics, women had double the prevalence of AD among men (10.9% vs. 5.4%). The prevalence of AD among African American men was more than two and a half times greater than the prevalence among white non-Hispanic men (14.4% vs. 5.4%). Age (p = 0.001), family history of AD (p = 0.02) and African American (p = 0.0001) or Cuban (p = 0.006) ethnic group were directly and independently associated with the prevalence of AD.

A three-factor model of cognition in Alzheimer disease.

OBJECTIVE: To use principal factors analysis to model cognition in Alzheimer disease. BACKGROUND: Earlier studies have used factor analysis to examine the effects on Alzheimer disease cognition of either heterogeneity in premorbid cognition or heterogeneity in the disease process itself. In the current study, both sources of heterogeneity were incorporated within a single model. METHODS: Two hundred sixty-one patients with probable Alzheimer disease (92 White Non-Hispanic, 148 Hispanic, and 21 African-American) were tested with the Mini-Mental Status Examination, the Assessment of Cognitive Abilities in Dementia, and the Short Portable Mental Status Examination. RESULTS: Three factors were obtained: one with loadings for memory and orientation, a second with loadings for language and praxis, and a third with loadings for executive functions. Factors 1 and 2 declined over 1.82 years (p = 0.0002, p = 0.0001); Factor 3 scores remained invariant over this period (p = 0.16). Furthermore, only Factor 3 scores correlated with either education (p = 0.0001) or ethnicity (p = 0.0001). CONCLUSIONS: A possible interpretation is that Factors 1 and 2 may reflect two components of the Alzheimer disease process while Factor 3 may provide an estimate of premorbid cognition. A potential practical application of the analysis is that it may provide a measure of Alzheimer disease decline that is free from correlation with education or ethnicity.

Relative frequencies of Alzheimer disease, Lewy body, vascular and frontotemporal dementia, and hippocampal sclerosis in the State of Florida Brain Bank.

Alzheimer disease (AD) is the most common dementing illness in the elderly, but there is equivocal evidence regarding the frequency of other disorders such as Lewy body disease (LBD), vascular dementia (VaD), frontotemporal dementia (FTD), and hippocampal sclerosis (HS). This ambiguity may be related to factors such as the age and gender of subjects with dementia. Therefore, the objective of this study was to calculate the relative frequencies of AD, LBD, VaD, FTD, and HS among 382 subjects with dementia from the State of Florida Brain Bank and to study the effect of age and gender on these frequencies. AD was the most frequent pathologic finding (77%), followed by LBD (26%), VaD (18%), HS (13%), and FTD (5%). Mixed pathology was common: Concomitant AD was present in 66% of LBD patients, 77% of VaD patients, and 66% of HS patients. The relative frequency of VaD increased with age, whereas the relative frequencies of FTD and LBD declined with age. Males were overrepresented among those with LBD, whereas females were overrepresented among AD subjects with onset age over 70 years. These estimates of the a priori probabilities of dementing disorders have implications for clinicians and researchers.