The relationships between age, sex, and the incidence of dementia and Alzheimer disease: a meta-analysis

BACKGROUND

Prevalence studies on dementia and Alzheimer disease (AD) have reported a positive association with age. However, the trend of the association in the oldest-old categories has been the subject of discussion. The relationship between sex and AD has been inconsistent with these studies. Prevalence rates are influenced by the survival and disease incidence. Incidence rates provide a better measure of disease risk.

METHODS

English-language articles identified through a MEDLINE search on "incidence dementia" and "incidence Alzheimer's disease" were examined and references from identified articles were reviewed. Population-based studies using personal interviews, standard clinical diagnosis criteria (DSM-III for dementia, National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorder Association for AD) and reporting age-specific incidence rates were included in the meta-analysis. Data from the selected studies were extracted and verified. Mixed-effect models were used in the meta-analysis to accommodate the heterogeneity of the studies.

RESULTS

Incident dementia and AD are associated with a significant quadratic age effect indicating that the increase in incidence rates slows down with the increase in age, although there is no sign of a decline in the incidence rates themselves. The odds ratios for women to develop incidence of dementia and AD relative to men are 1.18 (95% confidence interval, 0.95-1.46) and 1.56 (95% confidence interval, 1.16-2.10), respectively.

CONCLUSIONS

The acceleration of incidence rates for AD and dementia slows down with the increase in age, although we find no evidence of a rate decline. Women are at higher risk of developing AD than men.

Incidence of dementia and Alzheimer disease in 2 communities: Yoruba residing in Ibadan, Nigeria, and African Americans residing in Indianapolis, Indiana

CONTEXT

Alzheimer disease (AD) represents a major and increasing public health problem. If populations were identified with significantly lower or higher incidence rates of AD, the search for risk factors in the genesis of AD could be greatly enhanced.

OBJECTIVE

To compare incidence rates of dementia and AD in 2 diverse, elderly community-dwelling populations.

DESIGN

The Indianapolis-Ibadan Dementia Project, a longitudinal, prospective population-based study consisting of a baseline survey (1992-1993) and 2 subsequent follow-up waves after 2 years (1994-1995) and 5 years (1997-1998). Each wave followed a 2-stage design, with an in-home screening interview followed by a full diagnostic workup of a subsample of participants based on screening performance.

SETTING AND PARTICIPANTS

A total of 2459 community-dwelling Yoruba residents of Ibadan, Nigeria, without dementia, and 2147 community-dwelling African American residents of Indianapolis, Ind, without dementia (all aged 65 years or older). The cohorts were followed up for a mean of 5.1 years and 4.7 years, respectively.

MAIN OUTCOME MEASURES

Incident cases of dementia and AD in each of the 2 populations.

RESULTS

The age-standardized annual incidence rates were significantly lower among Yoruba than among African Americans for dementia (Yoruba, 1.35% [95% confidence interval [CI], 1.13%-1.56%]; African Americans, 3.24% [95% CI, 2.11%-4.38%]) and for AD (Yoruba, 1.15% [95% CI, 0.96%-1.35%]; African Americans, 2.52% [95% CI, 1.40%-3.64%]).

CONCLUSION

This is the first report of incidence rate differences for dementia and AD in studies of 2 populations from nonindustrialized and industrialized countries using identical methods and the same group of investigators in both sites. Further explorations of these population differences may identify potentially modifiable environmental or genetic factors to account for site differences in dementia and AD.

DSPP mutation in dentinogenesis imperfecta Shields type II

We identified a nonsense mutation (Gln45stop) in exon 3 of the dentin sialophosphoprotein (DSPP) gene in a Chinese family with dentinogenesis imperfecta Shields type II (DGI-II), in which the affected members showed discoloration and severe attrition of their teeth, with obliterated pulp chambers.

Intracranial stenosis in Chinese patients with acute stroke

We studied 100 consecutive acute stroke patients in a Chinese population with transcranial Doppler and CT. Twenty patients had intracerebral hemorrhage and 14 patients did not have adequate temporal windows for transcranial Doppler examination. Among the remaining 66 patients, 22 patients (33%) had intracranial occlusive diseases and 3 (6%) had extracranial carotid stenosis. Our data showed that intracranial occlusive disease is the most commonly found vascular lesion in our acute stroke patients.

Prevalence of cognitive impairment: data from the Indianapolis Study of Health and Aging

BACKGROUND

The epidemiology and natural history of cognitive impairment that is not dementia is important to the understanding of normal aging and dementia.

OBJECTIVE

To determine the prevalence and outcome of cognitive impairment that is not dementia in an elderly African American population.

METHOD

A two-phase, longitudinal study of aging and dementia. A total of 2212 community-dwelling African American residents of Indianapolis, IN, aged 65 and older were screened, and a subset (n = 351) received full clinical assessment and diagnosis. Subsets of the clinically assessed were seen again for clinical assessment and rediagnosis at 18 and 48 months. Weighted logistic regression was used to generate age-specific prevalence estimates.

RESULTS

The overall rate of cognitive impairment among community-dwelling elderly was 23.4%. Age-specific rates indicate increasing prevalence with increasing age: 19.2% for ages 65 to 74 years, 27.6% for ages 75 to 84 years, and 38.0% for ages 85+ years. The most frequent cause of cognitive impairment was medically unexplained memory loss with a community prevalence of 12.5%, followed by medical illness-associated cognitive impairment (4.0% prevalence), stroke (3.6% prevalence), and alcohol abuse (1.5% prevalence). At 18-month follow-up, 26% (17/66) of the subjects had become demented.

CONCLUSIONS

Cognitive impairment short of dementia affects nearly one in four community-dwelling elders and is a major risk factor for later development of dementia.

Self-assembly of DNA-streptavidin nanostructures and their use as reagents in immuno-PCR

The self-assembly of bis-biotinylated double-stranded DNA and the tetravalent biotin-binding protein streptavidin (STV) have been studied by non-denaturing gel electrophoresis and atomic force microscopy (AFM). The rapid self-assembly reproducibly generated populations of individual oligomeric complexes. Most strikingly, the oligomers predominantly contained bivalent STV molecules bridging two adjacent DNA fragments to form linear nanostructures. Trivalent STV branch points occurred with a lower frequency and the presence of tetravalent STV was scarce. However, valency distribution, size and the exchange dynamics of the supramolecular aggregates were highly sensitive to stoichiometric variations in the relative molar coupling ratio of bis-biotinylated DNA and STV. The largest aggregates were obtained from equimolar amounts while excess STV led to the formation of smaller oligomers appearing as fingerprint-like band patterns in electrophoresis. Excess DNA, however, induces a complete breakdown of the oligomers, likely a consequence of the instability of STV conjugates containing more than two biotinylated DNA fragments. It was demonstrated that the oligomers can further be functionalized, for instance by the coupling of biotinylated immunoglobulins. Both pure and also antibody-modified DNA-STV oligomers were used as reagents in immuno-PCR (IPCR), a highly sensitive detection method for proteins and other antigens. Employment of the supramolecular reagents led to an approximately 100-fold enhanced sensitivity compared to the conventional IPCR procedure.

Association of antioxidants with memory in a multiethnic elderly sample using the Third National Health and Nutrition Examination Survey

Oxidative stress has been implicated both in the aging process and in the pathological changes associated with Alzheimer's disease. Antioxidants, which have been shown to reduce oxidative stress in vitro, may represent a set of potentially modifiable protective factors for poor memory, which is a major component of the dementing disorders. The authors investigated the association between serum antioxidant (vitamins E, C, A, carotenoids, selenium) levels and poor memory performance in an elderly, multiethnic sample of the United States. The sample consisted of 4,809 non-Hispanic White, non-Hispanic Black, and Mexican-American elderly who visited the Mobile Examination Center during the Third National Health and Nutrition Examination Survey, a national cross-sectional survey conducted from 1988 to 1994. Memory is assessed using delayed recall (six points from a story and three words) with poor memory being defined as a combined score less than 4. Decreasing serum levels of vitamin E per unit of cholesterol were consistently associated with increasing levels of poor memory after adjustment for age, education, income, vascular risk factors, and other trace elements and minerals. Serum levels of vitamins A and C, beta-carotene, and selenium were not associated with poor memory performance in this study.

Universal standardization of bone density measurements: a method with optimal properties for calibration among several instruments

The International Dual-Photon X-Ray Absorptiometry (DXA) Standardization Committee (IDSC) conducted a cross-calibration study among three models of DXA machines from three different manufacturers. In that study, 100 subjects were scanned on all three machines. A set of equations were derived to convert bone mineral density (BMD) on each machine to a "standardized BMD" (sBMD) such that sBMD from the same subject derived from different machines would be approximately the same. In a reanalysis of the cross-calibration data, we showed that the conversion method used in the IDSC study did not achieve several optimal properties desirable in such conversions. We derived new conversion equations to sBMD based on minimizing differences among sBMD from the three machines. More important is that the new conversions have no residual bias that was present in the IDSC conversions. The performance of the methods were compared on the cross-calibration data as well as an external data set. We conclude that the IDSC conversions are adequate for clinical use on other machines worldwide, but that researchers should standardize their own machines in a laboratory using the new method.

Community screening interview for dementia (CSI 'D'); performance in five disparate study sites

The Community Screening Interview for Dementia (CSI 'D') was developed as a screening instrument for dementia for use in cross-cultural studies. It consists of two components, a cognitive test for non-literate and literate populations and an informant interview regarding performance in everyday living. The development of the CSI 'D', involving harmonization, translation, back translation and pilot testing, for use in five sites is described. The results demonstrate the adaptability and utility of the CSI 'D' in populations from very different socioeconomic backgrounds. The inclusion of informant data adds significantly to the performance of the CSI 'D' as a dementia screen. The combination of informant and cognitive scores in a discriminant score produces better sensitivity and specificity for dementia than cognitive scores alone. The informant score has a significant independent effect in predicting dementia.

Distinct roles for two G protein alpha subunits in fungal virulence, morphology, and reproduction revealed by targeted gene disruption

Reduced accumulation of the GTP-binding protein G(i)alpha subunit CPG-1, due either to hypovirus infection or transgenic cosuppression, correlates with virulence attenuation of the chestnut blight fungus, Cryphonectria parasitica. The role of G protein-mediated signal transduction in fungal virulence was further examined by targeted disruption of the gene cpg-1, encoding CPG-1, and a second Galpha gene, cpg-2, encoding the subunit CPG-2. Disruption of cpg-1 resulted in a set of phenotypic changes similar to, but more severe than, those associated with hypovirus infection. Changes included a marked reduction in fungal growth rate and loss of virulence, asexual sporulation, female fertility, and transcriptional induction of the gene lac-1, encoding the enzyme laccase. In contrast, cpg-2 disruption resulted in only slight reductions in growth rate and asexual sporulation and no significant reduction in virulence, female fertility, or lac-1 mRNA inducibility. These results provide definitive confirmation of previous correlative evidence that suggested a requirement of CPG-1-linked signaling for a number of fungal processes, including virulence and reproduction, while demonstrating that a second Galpha, CPG-2, is dispensable for these processes. They also significantly strengthen support for the apparent linkage between hypovirus-mediated disruption of G protein signal transduction and attenuation of fungal virulence.

Dehydrogenative coupling of phenanthroline under hydrothermal conditions: crystal structure of a novel layered vanadate complex constructed of 4,8,10-net sheets: [(2,2'-biphen)Co]V3O8.5

2,2'-Biphenanthroline (2,2'-biphen) formed from 1,10-phenanthroline when a new two-dimensional layered vanadium oxide metal coordination complex, [(2,2'-biphen)Co]V3O8.5, which contains novel 4,8,10-net sheets, was hydrothermally synthesized.

Serum cholesterol, APOE genotype, and the risk of Alzheimer's disease: a population-based study of African Americans

A significant interaction among total serum cholesterol (TC), APOE genotype, and AD risk was found in a population-based study of elderly African Americans. Increasing TC was associated with increased AD risk in the group with no epsilon4 alleles, whereas TC was not associated with increased AD risk in the group with one or more epsilon4 alleles. Further study of the relationship between cholesterol and APOE genotype is needed to confirm this association, but the results suggest that cholesterol may be a potentially modifiable environmental risk factor for AD.

Confidence intervals for the log-normal mean

In this paper we conduct a stimulation study to evaluate coverage error, interval width and relative bias of four main methods for the construction of confidence intervals of log-normal means: the naive method; Cox's method; a conservative method; and a parametric bootstrap method. The simulation study finds that the naive method is inappropriate, that Cox's method has the smallest coverage error for moderate and large sample sizes, and that the bootstrap method has the smallest coverage error for small sample sizes. In addition, Cox's method produces the smallest interval width among the three appropriate methods. We also apply the four methods to a real data set to contrast the differences.

Use of anticholinergics and the risk of cognitive impairment in an African American population

BACKGROUND

Anticholinergic properties of certain medications often go unrecognized, and are frequently used by the elderly population. Few studies have yet defined the long-term impact of these medications on the incidence of cognitive impairment.

METHODS

We report a 6-year longitudinal, observational study, evaluating 1,652 community-dwelling African American subjects over the age of 70 years who were enrolled in the Indianapolis-Ibadan Dementia Project between 2001 and 2007 and who had normal cognitive function at baseline. The exposure group included those who reported the baseline use of possible or definite anticholinergics as determined by the Anticholinergic Cognitive Burden scale. Our main outcome measure was the incidence of cognitive impairment, defined as either dementia or cognitive impairment not dementia, or poor performance on a dementia screening instrument during the follow-up period.

RESULTS

At baseline, 53% of the population used a possible anticholinergic, and 11% used a definite anticholinergic. After adjusting for age, gender, educational level, and baseline cognitive performance, the number of definite anticholinergics was associated with an increased risk of cognitive impairment (odds ratio [OR] 1.46, 95% confidence interval [CI] 1.07-1.99; p = 0.02), whereas the number of possible anticholinergics at baseline did not increase the risk (OR 0.96, 95% CI 0.85-1.09; p = 0.55). The risk of cognitive impairment among definite anticholinergic users was increased if they were not carriers of the APOE epsilon4 allele (OR 1.77, 95% CI 1.03-3.05; p = 0.04).

CONCLUSIONS

Limiting the clinical use of definite anticholinergics may reduce the incidence of cognitive impairment among African Americans.

Oxidative stress and the ovary

Superoxide (O(2)(-)), hydrogen peroxide (H(2)O(2)), and lipid peroxides are generated in luteal tissue during natural and prostaglandin-induced regression in the rat, and this response is associated with reversible depletion of ascorbic acid. Reactive oxygen species immediately uncouple the luteinizing hormone receptor from adenylate cyclase and inhibit steroidogenesis by interrupting transmitochondrial cholesterol transport. The cellular origin of oxygen radicals in regressing corpora lutea is predominantly from resident and infiltrated leukocytes, notably neutrophils. Reactive oxygen species are also produced within the follicle at ovulation and, like the corpus luteum, leukocytes are the major source of these products. Antioxidants block the resumption of meiosis, whereas the generation of reactive oxygen induces oocyte maturation in the follicle. Although oxygen radicals may serve important physiologic roles within the ovary, the cyclic production of these damaging agents over years may lead to an increased cumulative risk of ovarian pathology that would probably be exacerbated under conditions of reduced antioxidant status.

Ferrimagnetic-like ordering in a unique three-dimensional coordination polymer featuring mixed azide/carboxylate-bridged trinuclear manganese (II) clusters as subunits

The crystal structure of the coordination polymer [Mn3(N3)2(nta)4(H2O)2]n (nta = nicotinate) consists of trinuclear subunits bridged by mixed mu-1,1-azide and mu-carboxylate-O,O groups, which are linked by mu 3-nta-N,O,O ligands into a three-dimensional network exhibiting ferrimagnetic-like ordering.

DNA repair rates mapped along the human PGK1 gene at nucleotide resolution

The repair of cyclobutane pyrimidine dimers (CPDs), DNA lesions induced by ultraviolet light, was studied at nucleotide resolution. Human fibroblasts were irradiated with ultraviolet light and allowed to repair. The DNA was enzymatically cleaved at the CPDs, and the induced breaks along the promoter and exon 1 of the PGK1 gene were mapped by ligation-mediated polymerase chain reaction. Repair rates within the nontranscribed strand varied as much as 15-fold, depending on nucleotide position. Preferential repair of the transcribed strand began just downstream of the transcription start site but was most pronounced beginning at nucleotide +140 in exon 1. The promoter contained two slowly repaired regions that coincided with two transcription factor binding sites.

A new nerve guide conduit material composed of a biodegradable poly(phosphoester)

There is a resurgence of interest in the development of degradable and biocompatible polymers for fabrication of nerve guide conduits (NGCs) in recent years. Poly(phosphoester) (PPE) polymers are among the attractive candidates in this context, in view of their high biocompatibility, adjustable biodegradability, flexibility in coupling fragile biomolecules under physiological conditions and a wide variety of physicochemical properties. The feasibility of using a biodegradable PPE, P(BHET-EOP/TC), as a novel NGC material was investigated. Two types of conduits were fabricated by using two batches of P(BHET-EOP/TC) with different weight-average molecular weights (Mw) and polydispersity indexes (PI). The polymers as well as conduits were non-toxic to all six types of cells tested, including primary neurones and neuronally differentiated PC12 cells. After in situ implantation in the sciatic nerve of the rat, two types of conduits triggered a similar tissue response, inducing the formation of a thin tissue capsule composed of approximately eight layers of fibroblasts surrounding the conduits at 3 months. Biological performances of the conduits were examined in the rat sciatic nerve model with a 10 mm gap. Although tube fragmentation, even tube breakage, was observed within less than 5 days post-implantation, successful regeneration through the gap occurred in both types of conduits, with four out of 10 in the Type I conduits (Mw 14,900 and PI 2.57) and 11 out of 12 in the Type II conduits (Mw 18,900 and PI 1.72). The degradation of conduits was further evidenced by increased roughness on the tube surface in vivo under scanning electron microscope and a mass decrease in a time-dependent manner in vitro. The Mw of the polymers dropped 33 and 24% in the Type I and II conduits, respectively, in vitro within 3 months. Among their advantages over other biodegradable NGCs, the PPE conduits showed negligible swelling and no crystallisation after implantation. Thus, these PPE conduits can be effective aids for nerve regeneration with potential to be further developed into more sophisticated NGCs that have better control of the conduit micro-environment for improved nerve regeneration.

Mechano-dependent signaling by Latrophilin/CIRL quenches cAMP in proprioceptive neurons

Adhesion-type G protein-coupled receptors (aGPCRs), a large molecule family with over 30 members in humans, operate in organ development, brain function and govern immunological responses. Correspondingly, this receptor family is linked to a multitude of diverse human diseases. aGPCRs have been suggested to possess mechanosensory properties, though their mechanism of action is fully unknown. Here we show that the Drosophila aGPCR Latrophilin/dCIRL acts in mechanosensory neurons by modulating ionotropic receptor currents, the initiating step of cellular mechanosensation. This process depends on the length of the extended ectodomain and the tethered agonist of the receptor, but not on its autoproteolysis, a characteristic biochemical feature of the aGPCR family. Intracellularly, dCIRL quenches cAMP levels upon mechanical activation thereby specifically increasing the mechanosensitivity of neurons. These results provide direct evidence that the aGPCR dCIRL acts as a molecular sensor and signal transducer that detects and converts mechanical stimuli into a metabotropic response.

Vascular lesions in Chinese patients with transient ischemic attacks

We studied 96 Chinese patients with TIAs using transcranial Doppler and duplex ultrasonography. We found intracranial stenosis or occlusion in 51% of cases and extracranial disease in 19% of cases. The most common intracranial lesion was stenosis of the terminal internal carotid artery or proximal middle cerebral artery, whereas the most common extracranial lesion was stenosis of the carotid bifurcation.

Asymptomatic microbleeds as a risk factor for aspirin-associated intracerebral hemorrhages

The authors measured the presence and extent of asymptomatic microbleeds on gradient-recalled-echo MRI in 21 aspirin users who developed intracerebral hemorrhage and 21 aspirin users without history of intracerebral hemorrhage. Microbleeds were more frequent (19 vs 7, p < 0.001) and more extensive (mean number of microbleeds 13.3 vs 0.4, p < 0.001) in the intracerebral hemorrhage group than in the control group. Asymptomatic microbleeds may be a risk factor for aspirin-associated intracerebral hemorrhage.

Validation of germination rate and root elongation as indicator to assess phytotoxicity with Cucumis sativus

Germination rate and root elongation, as a rapid phytotoxicity test method, possess several advantages, such as sensitivity, simplicity, low cost and suitability for unstable chemicals or samples. These advantages made them suitable for developing a large-scale phytotoxicity database and especially applicable for developing quantitative structure-activity relationship (QSAR) to study mechanisms of phytotoxicity. In this paper, the comparative inhibition of germination rate and root elongation of Cucumis sativus by selected halogen-substituted phenols and anilines were determined. The suitability of germination rate and root elongation as phytotoxicity endpoints was evaluated. Excellent reproducibility and stability of germination rate and root elongation in the control test, relatively greater sensitivity and similar dose-response relations for all tested compounds were observed. These results together with those of a 2-day test were used to demonstrate the suitability of this phytotoxicity test method. A QSAR was developed for the phytotoxicity mode of action of the tested compounds to C sativus seeds. Models that combined the logarithm of 1-octanol/water partition coefficient (log Kow) and the energy of the lowest unoccupied molecular orbital (Elumo) were developed for both germination rate inhibition and root elongation inhibition. The results of these studies indicate that phytotoxicity of substituted phenols and anilines to C. sativus seeds could be explained by a polar narcosis mechanism. This paper will promote the application of germination rate and root elongation method and the development of large-scale phytotoxicity database, which will provide the fundamental data for QSAR and ecological risk assessment of organic pollutants.