Refractive errors in a black adult population: the Barbados Eye Study.
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PURPOSE: To describe the prevalence of refractive errors in a black adult population. METHODS: The Barbados Eye Study, a population-based study, included 4709 Barbados-born citizens, or 84% of a random sample, 40 to 84 years of age. Myopia and hyperopia were defined as a spherical equivalent <-0.5 diopters and >+0.5 diopters, respectively, based on automated refraction. Analyses included 4036 black participants without history of cataract surgery. Associations with myopia and hyperopia were evaluated in logistic regression analyses. RESULTS: The prevalence of myopia was 21.9% and was higher in men (25.0%) than in women (19.5%). The prevalence of hyperopia was 46.9% and was higher in women (51.8%) than in men (40.5%). The prevalence of myopia decreased from 17% in persons 40 to 49 years of age to 11% in those 50 to 59 years of age, but increased after 60 years of age. The prevalence of hyperopia increased from 29% at 40 to 49 years of age to 65% at 50 to 59 years of age, and tended to decline thereafter. A higher prevalence of myopia was positively associated (P < 0.05) with lifetime occupations requiring nearwork, nuclear opacities, posterior subcapsular opacities, glaucoma, and ocular hypertension. Factors associated with hyperopia were the same as for myopia, except for occupation, and in the opposite direction. CONCLUSIONS: High prevalences of myopia and hyperopia were found in this large black adult population. The prevalence of myopia (hyperopia) increased (decreased) after 60 years of age, which is inconsistent with data from other studies. The high prevalence of age-related cataract, glaucoma, and other eye conditions in the Barbados Eye Study population may contribute to the findings. (+info)
Connectivity of marine populations: open or closed?
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Most marine populations are thought to be well connected via long-distance dispersal of larval stages. Eulerian and Lagrangian flow models, coupled with linear mortality estimates, were used to examine this assumption. The findings show that when simple advection models are used, larval exchange rates may be overestimated; such simplistic models fail to account for a decrease of up to nine orders of magnitude in larval concentrations resulting from diffusion and mortality. The alternative process of larval retention near local populations is shown to exist and may be of great importance in the maintenance of marine population structure and management of coastal marine resources. (+info)
Detection of dengue infection in patients investigated for leptospirosis in Barbados.
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The annual incidence of leptospirosis in Barbados is approximately 13 severe cases/100,000. The peak incidence occurs in October to December of each year, coinciding with the months of heaviest rainfall. During the second half of 1995, an epidemic of dengue type 1 infection produced almost 1,000 laboratory-confirmed cases. During the same period, leptospirosis mortality was twice the average, suggesting that some cases of leptospirosis were being misdiagnosed and treated inappropriately. Sera from patients investigated for dengue or leptospirosis were analyzed retrospectively to determine the extent of misdiagnosis. During 1995 and 1996, 31 of 139 and 29 of 93 patients, respectively, were confirmed as having leptospirosis. Sera from the remaining leptospirosis-negative patients were tested for IgM antibodies to dengue virus. During 1995 and 1996, 48 of 108 patients and 21 of 64 patients, respectively, were found to have dengue. In 1997, sera from all patients investigated for leptospirosis were also tested prospectively for IgM antibodies to dengue: 38 of 92 leptospirosis-negative patients (41%) were dengue IgM-positive, while 2 of 25 leptospirosis cases also had serologic evidence suggesting acute dengue infection. A second large outbreak of dengue caused by serotype 2 occurred in 1997. During the 1995 and 1997 dengue epidemics in Barbados, dengue cases outnumbered leptospirosis cases investigated in the leptospirosis diagnostic protocol. During 1997, patients investigated but negative for dengue were also tested for anti-leptospiral IgM: 7.3% (19 of 262) were IgM-positive. Substantial misdiagnosis of both dengue and leptospirosis can occur and greater public awareness and clinical suspicion of the similar presentations of these two diseases are necessary. (+info)
Observed versus indirect estimates of incidence of open-angle glaucoma.
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Incidence data on open-angle glaucoma (OAG) are limited and difficult to obtain. To date, few studies have reported incidence directly measured from population-based cohorts. Other reported estimates have been derived indirectly from age-specific prevalence by using several assumptions, and their validity is unknown. To the authors' knowledge, this report presents the first comparison of observed versus indirect estimates of OAG incidence based on data from the population-based Barbados Incidence Study of Eye Diseases (1992-1997) (n = 3,427; 85% participation). The observed 4-year incidence of OAG was 1.2% (95% confidence interval (CI): 0.6, 2.1%) at ages 40-49 years, 1.5% (95% CI: 0.8, 2.5%) at ages 50-59 years, 3.2% (95% CI: 2.0, 4.8%) at ages 60-69 years, and 4.2% (95% CI: 2.6, 6.3%) in persons at ages 70 or more years. When incidence was calculated from the prevalence data, power function fitting achieved a closer approximation to observed incidence than did logistic curve fitting. Calculated incidence rates for each group were similar when assuming mortality that was equal (incidence rate = 0.7, 1.3, 2.3, and 4.8%) or differential (incidence rate = 0.7, 1.2, 2.4, and 4.8%). Other nonlogistic approaches also increased the resemblance of observed and calculated estimates. In the absence of longitudinal data, reasonably valid incidence estimates of OAG were obtained from available prevalence data. These estimation techniques can be useful when OAG incidence estimates are required for research or public health purposes. (+info)
Multipoint linkage-disequilibrium-mapping approach based on the case-parent trio design.
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In the present study we propose a multipoint approach, for the mapping of genes, that is based on the case-parent trio design. We first derive an expression for the expected preferential-allele-transmission statistics for transmission, from either parent to an affected child, for an arbitrary location within a chromosomal region demarcated by several genetic markers. No assumption about genetic mechanism is needed in this derivation, beyond the assumption that no more than one disease gene lies in the region framed by the markers. When one builds on this representation, the way in which one may maximize the genetic information from multiple markers becomes obvious. This proposed method differs from the popular transmission/disequilibrium test (TDT) approach for fine mapping, in the following ways: First, in contrast with the TDT approach, all markers contribute information, regardless of whether the parents are heterozygous at any one marker, and incomplete trio data can be utilized in our approach. Second, rather than performing the TDT at each marker separately, we propose a single test statistic that follows a chi(2) distribution with 1 df, under the null hypothesis of no linkage or linkage disequilibrium to the region. Third, in the presence of linkage evidence, we offer a means to estimate the location of the disease locus along with its sampling uncertainty. We illustrate the proposed method with data from a family study of asthma, conducted in Barbados. (+info)
Congenital afibrinogenemia: mutations leading to premature termination codons in fibrinogen A alpha-chain gene are not associated with the decay of the mutant mRNAs.
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Congenital afibrinogenemia is a rare coagulation disorder with autosomal recessive inheritance, characterized by the complete absence or extremely reduced levels of fibrinogen in patients' plasma and platelets. Eight afibrinogenemic probands, with very low plasma levels of immunoreactive fibrinogen were studied. Sequencing of the fibrinogen gene cluster of each proband disclosed 4 novel point mutations (1914C>G, 1193G>T, 1215delT, and 3075C>T) and 1 already reported (3192C>T). All mutations, localized within the first 4 exons of the A alpha-chain gene, were null mutations predicted to produce severely truncated A alpha-chains because of the presence of premature termination codons. Since premature termination codons are frequently known to affect the metabolism of the corresponding messenger RNAs (mRNAs), the degree of stability of each mutant mRNA was investigated. Cotransfection experiments with plasmids expressing the wild type and each of the mutant A alpha-chains, followed by RNA extraction and semiquantitative reverse-transcriptase-polymerase chain reaction analysis, demonstrated that all the identified null mutations escaped nonsense-mediated mRNA decay. Moreover, ex vivo analysis at the protein level demonstrated that the presence of each mutation was sufficient to abolish fibrinogen secretion. (+info)
Direct determination of the timing of sea level change during termination II.
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An outcrop within the last interglacial terrace on Barbados contains corals that grew during the penultimate deglaciation, or Termination II. We used combined 230Th and 231Pa dating to determine that they grew 135.8 +/- 0.8 thousand years ago, indicating that sea level was 18 +/- 3 meters below present sea level at the time. This suggests that sea level had risen to within 20% of its peak last-interglacial value by 136 thousand years ago, in conflict with Milankovitch theory predictions. Orbital forcing may have played a role in the deglaciation, as may have isostatic adjustments due to large ice sheets. Other corals in the same outcrop grew during oxygen isotope (delta18O) substage 6e, indicating that sea level was 38 +/- 5 meters below present sea level, about 168.0 thousand years ago. When compared to the delta18O signal in the benthic V19-30/V19-28 record at that time, the coral data extend to the previous glacial cycle the conclusion that deep-water temperatures were colder during glacial periods. (+info)
Diabetes in a Caribbean population: epidemiological profile and implications.
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OBJECTIVE: To examine the distribution and impact of diabetes, glycaemic status, and related factors, in a predominantly black adult Caribbean population. METHODS: The study included 4709 people, or 84% of a simple random sample of Barbadian-born citizens aged 40-84 years, examined between 1988 and 1992 and re-assessed 4 years later. Diabetes was evaluated according to physician-diagnosis and glycosylated haemoglobin (GHb). Associations were assessed by logistic regression analyses, cumulative mortality by product-limit methods and death-rate ratios by Cox proportional hazards regression. RESULTS: Among the 4314 black participants, the prevalence of known diabetes, predominantly type 2, was 9.1% at 40-49 years of age and increased to 24.0% at 70-79 years. The overall prevalence was 17.5%, while it was 12.5% in mixed (black/ white; n = 184) and 6.0% in white/other participants (n = 133), only 0.3% had younger-onset. Additionally, 2% had GHb >10% (>2 SD over the mean) without diabetes history. Sulphonylureas were the most frequent treatment, while insulin use was infrequent. In black participants, diabetes was positively associated with age (OR = 1.03 per year; 95% CI : 1.02-1.04), diabetes family history (OR = 2.85, 95% CI : 2.39-3.40), hypertension (OR = 1.71, 95% CI : 1.42-2.05), obesity (BMI > or = 25 kg/m(2); OR = 1.74, 95% CI : 1.44-2.10), and high waist-hip ratio (WHR > or = 0.92; OR = 1.29, 95% CI : 1.09-1.53). Ocular co-morbidities were increased among people with diabetes, as was 4-year-mortality (death rate ratio = 1.42, 95% CI : 1.10-1.83). There was a 9% increase in mortality for each 1% increase in GHb (death rate ratio = 1.09, 95% CI : 1.04-1.15). CONCLUSIONS: A markedly high prevalence of diabetes existed in the adult black population, affecting almost one in five people and increasing morbidity and mortality. Prevention strategies are urgently needed to reduce the adverse implications of diabetes in this and similar populations. (+info)