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P W Davidson

Publications and source records attributed to P W Davidson.

At least 19 recordsLinked to original sources
PubMed2003

Identifying bipolar disorders in individuals with intellectual disability.

OBJECTIVE: The aim of the present study was to characterize adults with intellectual disability (ID) and concomitant clinical diagnoses of bipolar disorder (BPD), and determine whether DSM-IV criteria would distinguish individuals with BPD from patients with other psychiatric diagnoses. METHODS: A retrospective chart review was done of a convenience sample of adult patients seen over a 3-year period in a specialty clinic for adults with ID and psychiatric disorders. The DSM-IV criteria were used to differentiate individuals with clinical symptoms of BPD from groups of patients with other mood or thought disorders with behavioural symptoms which frequently overlap those of BPD. Behavioural symptoms were also catalogued and used to distinguish the diagnostic groups. RESULTS: Subjects with clinical symptoms of BPD had significantly more DSM-IV mood-related and non-mood-related symptoms, as well as functional impairments, compared to individuals with major depression, depression with psychosis or schizophrenia/psychosis NOS (not otherwise specified). Likewise, behavioural profiles of the BPD group of patients differed significantly from patients in the other three groups. CONCLUSIONS: Bipolar disorder can be readily recognized and distinguished from other behavioural and psychiatric diagnoses in individuals with ID, and DSM-IV criteria can be useful in the diagnosis of BPD.

Adult↗
PubMed2003

Associations between behavior disorders and health status among older adults with intellectual disability.

Few studies have examined the relationship of behavior and health status among aging persons with intellectual and developmental disabilities (I/DD). Behavioral disorders, which often are coincident with functional decline in older persons with I/DD, may be more related to medical morbidity than previously reported. This cross-sectional study examined the association between health status and behavior disorders with increasing age in a cohort of 60,752 adults with I/DD clustered into four adult-age groupings (21-44, 45-59, 60-74, and >74). Age grouping data suggested an association between morbidity and increased likelihood of behavior symptoms in all but the oldest age grouping. The magnitude of the association and trend varied by specific disease across age groupings compared to that found in healthy cohorts. About 25% of the adults with I/DD had psychiatric diagnoses and the frequency of such diagnoses did not decrease with age grouping. These results suggest that adverse health status may increase the likelihood of persistent behavioral disturbances in older persons with I/DD. Moreover, behavioral disorders may be sentinels for occult medical morbidity, which in turn may be responsive to intervention.

Adult↗
PubMed2002

Health characteristics and health services utilization in older adults with intellectual disability living in community residences.

BACKGROUND: The health status and health needs of adults with intellectual disability (ID) change with advancing age, and are often accompanied by difficulties with vision, hearing, mobility, stamina and some mental processes. AIM: The present study collected health status information on a large cohort of adults with ID aged > or = 40 years living in small group, community-based residences in two representative areas of New York State, USA. METHOD: Adult group home residents with ID aged between 40 and 79 years (n = 1371) were surveyed to determine their health status and patterns of morbidity. RESULTS: Most subjects were characterized as being in good health. The frequency of cardiovascular, musculoskeletal and respiratory conditions, and sensory impairments increased with age, while neurological, endocrine and dermatological diseases did not. Psychiatric and behavioural disorders declined with increasing age, at least through 70 years of age. Although most conditions increased with age, their frequency varied by sex and level of ID. Frequencies of age-related organ system morbidity were compared to data from the National Health and Nutrition Evaluation Survey III. It was found that adults with ID had a lower overall reported frequency of cardiovascular risk factors, including hypertension and hyperlipidaemia, and adult-onset diabetes. Inconsistencies with mortality data among older adults with ID were observed (which showed equal if not greater prevalence of deaths as a result of cardiovascular disease and cancer). CONCLUSION: These results suggest that either a cohort effect is operating (i.e. contemporary populations are healthier than previous populations), or that there may be under-recognition of select risk factors and diseases.

Adult↗
PubMed2000

Twenty-seven years studying the human neurotoxicity of methylmercury exposure.

Research at the University of Rochester (U of R) has been focused on mercury for nearly half a century. Initially studies focused on dosimetry, especially the accuracy of measuring exposure, and experimental work with animal models. Clinical studies in human populations started when the U of R mercury group was asked to assist with dosimetry in the Iraq epidemic of 1971-1972. Initial clinical studies described the effects of methylmercury (MeHg) poisoning on adults and children. A dose-response curve for prenatal exposure was determined and it suggested that relatively low exposures might be harmful to the fetus. Since most human exposure to MeHg is dietary from fish consumption, these theoretical dangers had far-reaching implications. After Iraq, the Rochester team pursued exposure from fish consumption in both adults and children. Populations with high fish consumption were identified in Samoa and Peru for studying adults and in Peru and the Seychelles islands for studying children. The possible health threat to the fetus from maternal fish consumption quickly became the focus of research efforts. This paper reviews the Rochester experience in studying human exposure to MeHg from fish consumption.

Adult↗
PubMed2000

Association between methylmercury exposure from fish consumption and child development at five and a half years of age in the Seychelles Child Development Study: an evaluation of nonlinear relationships.

Studies to date of the developmental effects of pre- and postnatal methylmercury exposure from fish consumption in the Seychelles Islands, using linear regression models for analysis, have not shown adverse effects on neurodevelopmental test scores. In this study we evaluated whether nonlinear effects of methylmercury exposure were present, using scores on six tests administered to cohort children in the Seychelles Child Development Study at 66 months of age. Prenatal exposure was determined by measuring mercury in a segment of maternal scalp hair representing growth during pregnancy. Postnatal exposure was measured in a segment of the child's hair taken at 66-months of age. Generalized additive models (GAMs), which make no assumptions about the functional form of the relationship between exposure and test score, were used in the analysis. GAMs similar to the original linear regression models were used to reanalyze the six primary developmental endpoints from the 66-month test battery. Small nonlinearities were identified in the relationships between prenatal exposure and the Preschool Language Scale (PLS) Total score and Child Behavior Check List (CBCL) and between postnatal exposure and the McCarthy General Cognitive Index (GCI) test scores. The effects are best described graphically but can be summarized by computing the change in the predicted test score from 0 to either 10 or 15 ppm and then above this point. For the PLS the trend involved a decline of 0.8 points between 0 and 10 ppm followed by an increase (representing improvement) of 1.3 points above 10 ppm. For the CBCL there was an increase of 1 point from 0 to 15 ppm, and then a decline (improvement) of 4 points above 15 ppm. The GCI increased by 1.8 points through 10 ppm and then declined 3.2 points (representing worse performance) above 10 ppm. These results are not entirely consistent. Two of the trends involve what appear to be beneficial effects of prenatal exposure. The one possibly adverse trend involves postnatal exposure. In every case the trend changes direction, so that an effect in one direction is followed by an effect in the opposite direction. Because of the descriptive nature of GAMs it is difficult to provide a precise level of statistical significance for the estimated trends. Certainly above 10 ppm there is less data and trends above this level are estimated less precisely. Overall there was no clear evidence for consistent (across the entire range of exposure levels) adverse effects of exposure on the six developmental outcomes. Further nonlinear modeling of these data may be appropriate, but there is also the risk of fitting complex models without a clear biological rationale.

Animals↗
PubMed2000

Neurodevelopmental outcomes of Seychellois children from the pilot cohort at 108 months following prenatal exposure to methylmercury from a maternal fish diet.

The Seychelles Child Development Study has been unable to confirm any relationship between maternal exposure to MeHg during pregnancy and adverse developmental outcomes. In this report, 87 children from a pilot cohort were evaluated at 9 years of age. Each child was given a battery testing specific cognitive, visual motor, and motor skills using standardized psychometric and neuro-psychological tests. The results indicated no adverse association between maternal MeHg exposure and any developmental outcome measure. For three endpoints (Boston Naming Test and two tests of visual motor coordination), enhanced performance in males was associated with increasing prenatal MeHg exposure. A secondary analysis including both prenatal MeHg and postnatal MeHg exposure was done even though we lacked postnatal hair for about 35% of the cohort. The results of the secondary analysis mirrored the outcomes of the primary analysis regarding prenatal exposure but were less robust. The results of this study are consistent with earlier findings from the 66-month evaluations of the SCDS Main cohort. Since MeHg is neurotoxic, this effect is likely due to other factors associated with consumption of fish.

Adult↗
PubMed2000

Secondary analysis from the Seychelles Child Development Study: the child behavior checklist.

Human exposure to methylmercury (MeHg), a known neurotoxin, is primarily from fish consumption. As part of a large study examining the association between MeHg exposure and child development in a population with high fish consumption we examined school-age behavior using the Achenbach Child Behavior Checklist (CBCL). The CBCL Total T score was a primary endpoint and was reported earlier to show no adverse association with prenatal or postnatal MeHg exposure. In this study we analyzed the T scores of the CBCL subscales to determine if more discrete aspects of measured behavior were associated with exposure. The Seychelles Child Development Study (SCDS) is a prospective, double blind, longitudinal evaluation of over 700 children. The index of prenatal exposure was maternal hair total mercury (T-Hg) in a segment growing during gestation. Postnatal exposure was T-Hg in the child's hair taken at 66 months of age. The child's primary caregiver completed the CBCL during the 66-month evaluation. No association between prenatal or postnatal MeHg exposure and the CBCL subscales was found. In Seychellois children exposed to MeHg from consumption of ocean fish we found no association between either prenatal or postnatal MeHg exposure and behavior as measured by the CBCL subscales.

Adult↗
PubMed2000

Association between prenatal exposure to methylmercury and cognitive functioning in Seychellois children: a reanalysis of the McCarthy Scales of Children's Ability from the main cohort study.

Methylmercury (MeHg) is a neurotoxicant whose high-dose effects first became known following a number of poisoning outbreaks that occurred worldwide. The primary human exposure is low dosage from fish consumption. Studies of fish-eating populations have not found a consistent pattern of association between exposures and outcomes. Therefore, examining specific areas of cognitive functioning has been suggested as an important approach to determine whether more subtle effects of MeHg exposure are present. In the Seychelles longitudinal study of prenatal and postnatal MeHg exposure from fish consumption and development, the McCarthy Scales of Children's Abilities (MSCA) were administered to children at age 66 months. No association between MeHg exposure and performance on the MSCA General Cognitive Index was identified. We analyzed these data further to determine whether associations were present on specific subscales of the MSCA. The standard MSCA subscales were analyzed. Then, more specific subscales of the MSCA were defined and analyzed utilizing a neuropsychological approach. The subscales were recombined to approximate the domains of cognitive functioning evaluated in the Faroes and New Zealand studies. Analyses of both the standard and the recombined MSCA subscales showed no adverse associations with MeHg exposure and neuropsychological endpoints. A positive association between postnatal MeHg exposure and performance on the MSCA Memory subscale was found. These findings are consistent with previous reports from the Seychelles study in that no adverse effects of MeHg exposure from fish consumption can be detected in this cohort.

Animals↗
PubMed2000

Benchmark concentrations for methylmercury obtained from the Seychelles Child Development Study.

Methylmercury is a neurotoxin at high exposures, and the developing fetus is particularly susceptible. Because exposure to methylmercury is primarily through fish, concern has been expressed that the consumption of fish by pregnant women could adversely affect their fetuses. The reference dose for methylmercury established by the U.S. Environmental Protection Agency was based on a benchmark analysis of data from a poisoning episode in Iraq in which mothers consumed seed grain treated with methylmercury during pregnancy. However, exposures in this study were short term and at much higher levels than those that result from fish consumption. In contrast, the Agency for Toxic Substances and Disease Registry (ATSDR) based its proposed minimal risk level on a no-observed-adverse-effect level (NOAEL) derived from neurologic testing of children in the Seychelles Islands, where fish is an important dietary staple. Because no adverse effects from mercury were seen in the Seychelles study, the ATSDR considered the mean exposure in the study to be a NOAEL. However, a mean exposure may not be a good indicator of a no-effect exposure level. To provide an alternative basis for deriving an appropriate human exposure level from the Seychelles study, we conducted a benchmark analysis on these data. Our analysis included responses from batteries of neurologic tests applied to children at 6, 19, 29, and 66 months of age. We also analyzed developmental milestones (age first walked and first talked). We explored a number of dose-response models, sets of covariates to include in the models, and definitions of background response. Our analysis also involved modeling responses expressed as both continuous and quantal data. The most reliable analyses were considered to be represented by 144 calculated lower statistical bounds on the benchmark dose (BMDLs; the lower statistical bound on maternal mercury hair level corresponding to an increase of 0.1 in the probability of an adverse response) derived from the modeling of continuous responses. The average value of the BMDL in these 144 analyses was 25 ppm mercury in maternal hair, with a range of 19 to 30 ppm.

Animals↗
PubMed2000

Does methylmercury have a role in causing developmental disabilities in children?

Methylmercury (MeHg) is a potent neurotoxin that in high exposures can cause mental retardation, cerebral palsy, and seizures. The developing brain appears particularly sensitive to MeHg. Exposure levels in pregnant experimental animals that do not result in detectable signs or symptoms in the mother can adversely affect the offspring's development. Studies of human poisonings suggest this may also occur in humans. Human exposure to MeHg is primarily dietary through the consumption of fish: MeHg is present in all fresh and saltwater fish. Populations that depend on fish as a major source of dietary protein may achieve MeHg exposure levels hypothesized to adversely affect brain development. Increasing mercury levels in the environment have heightened concerns about dietary exposure and a possible role for MeHg in developmental disabilities. Follow-up studies of an outbreak of MeHg poisoning in Iraq revealed a dose-response relationship for prenatal MeHg exposure. That relationship suggested that prenatal exposure as low as 10 ppm (measured in maternal hair growing during pregnancy) could adversely affect fetal brain development. However, using the same end points as were used in the Iraq study, no associations have been reported in fish-eating populations. Using a more extensive range of developmental end points, some studies of populations consuming seafood have reported associations with prenatal MeHg exposure, whereas others have found none. This paper reviews the data presently available associating MeHg exposure with development and poses some of the unanswered questions in this field.

Animals↗
PubMed2000

Evaluation of techniques for assessing neurobehavioral development in children.

A battery of tests has been designed to explore functional disabilities in children 10-12 years of age arising from adverse conditions during early development. At these ages, it becomes possible to use more complex and challenging tests than those typically used at earlier ages. Although the battery was prompted originally by questions arising from methylmercury exposure, it was also designed for applicability to neurotoxicant exposures arising from pesticides, solvents, persistent organic pollutants such as PCBs and dioxins, other metals, and nutrient excesses and deficiencies as well. The test battery includes the following categories: (1) neuropsychological tests with established psychometric properties not widely exploited in studies of developmental neurotoxicity; (2) electrophysiological and behavioral tests of sensory functioning spanning a broader range of indices than those used generally in studies of neuropsychological development; and (3) adaptations of performance tasks used previously only in animals. The battery was developed in Rochester, New York, and then field-tested on a group of 61 children in the Republic of the Seychelles, where the Ministry of Health had established the Child Development Center. Our findings suggest a number of tests and procedures with the potential for inclusion in test batteries aimed at the exploration of adverse neurodevelopmental effects.

Adolescent↗
PubMed1999

Characteristics of older adults with intellectual disabilities referred for crisis intervention.

The aim of the present study was to identify the age correlates of behavioural crises in adults with intellectual disability (ID) living in the community. The cohort consisted of 185 clients (IQ < 70), ranging in age from 20 to > 70 years, who were referred to a crisis intervention programme specializing in services to individuals with dual diagnosis over a 7-year period. A retrospective cross-sectional analysis of historical and contemporaneous variables was completed. Referrals for crisis intervention were not related to the age of the client Aggression and non-compliant behaviour occurred with similar frequency in all age groups. Other behaviours, including withdrawal, self-injury, stereotypy and symptoms of psychiatric disorders, occurred less often in older clients. Severity of ID affected the pattern of behavioural crises that resulted in referral. The results suggest that people with ID residing in community settings still experience behavioural crises as they grow older. Confirmation of the trends reported in the present study might signal a need for accelerating the development of comprehensive age-span community mental health and behavioural supports.

Adult↗
PubMed1999

Association between prenatal exposure to methylmercury and developmental outcomes in Seychellois children: effect modification by social and environmental factors.

UNLABELLED: The Seychelles Child Development Study (SCDS) is testing the hypothesis that prenatal exposure to low doses of MeHg from maternal consumption of fish is associated with the child's developmental outcomes. No deleterious relationships between exposure to MeHg and cognitive functions have been identified in the primary analysis of the main cohort through 66 months of age. We performed secondary analyses to determine if effect modification (EM) from social and environmental factors was affecting associations between MeHg and outcomes. METHODS: MeHg exposure was determined by analysis of maternal hair growing during pregnancy. Children in our Main Study cohort were evaluated at 6.5 months (N = 740) for visual recognition memory and visual attention using the Fagan Infantest, at 19 months (N = 738) and 29 months (N = 736) with the Bayley Scales of Infant Development (BSID). Interactions between MeHg and Caregiver Intelligence, Family Income and Home Environment were examined by multiple regression analysis. RESULTS: The median prenatal MeHg exposure was 5.9 ppm (Range 0.5-26.7 ppm). No EM occurred for preferential looking or visual attention at 6.5 months, for the BSID Psychomotor Scale at either 19 or 29 months, or for activity level at 29 months as measured by the BSID Infant Behavior Record. Interactions between MeHg level and both caregiver intelligence and family income were statistically significant for the BSID Mental Scale at 19 months but not at 29 months. These showed enhancement of MDI scores with increasing maternal MeHg in higher caregiver IQ groups at several levels of family income. CONCLUSIONS: In Seychellois children, consistent major EM by social or environmental factors were not identified. The small EM by caregiver intelligence and social factors at 19 months is consistent with the enhanced performance we reported when this cohort was examined at 66 months.

Attention↗
PubMed1998

Effects of prenatal and postnatal methylmercury exposure from fish consumption on neurodevelopment: outcomes at 66 months of age in the Seychelles Child Development Study.

CONTEXT: Human neurodevelopmental consequences of exposure to methyl-mercury (MeHg) from eating fish remain a question of public health concern. OBJECTIVE: To study the association between MeHg exposure and the developmental outcomes of children in the Republic of Seychelles at 66 months of age. DESIGN: A prospective longitudinal cohort study. PARTICIPANTS: A total of 711 of 779 cohort mother-child pairs initially enrolled in the Seychelles Child Development Study in 1989. SETTING: The Republic of Seychelles, an archipelago in the Indian Ocean where 85% of the population consumes ocean fish daily. MAIN OUTCOME MEASURES: Prenatal and postnatal MeHg exposure and 6 age-appropriate neurodevelopmental tests: the McCarthy Scales of Children's Abilities, the Preschool Language Scale, the Woodcock-Johnson Applied Problems and Letter and Word Recognition Tests of Achievement, the Bender Gestalt test, and the Child Behavior Checklist. RESULTS: The mean maternal hair total mercury level was 6.8 ppm and the mean child hair total mercury level at age 66 months was 6.5 ppm. No adverse outcomes at 66 months were associated with either prenatal or postnatal MeHg exposure. CONCLUSION: In the population studied, consumption of a diet high in ocean fish appears to pose no threat to developmental outcomes through 66 months of age.

Central Nervous System Diseases↗
PubMed1998

Mercury in fish.

Explore the source record for details and available documents.

Animals↗
PubMed1998

Effects of providing comprehensive ambulatory services to children with chronic conditions.

OBJECTIVE: To document the effects of a comprehensive program of care on the resource utilization and cost of care for children with chronic conditions. DESIGN: Descriptive study of 10715 admissions between 1984 and 1995 with analyses of costs based on charges. Comparisons were made with data from a national consortium of academic medical centers and from a national survey of hospitals. A 2-week survey of staff was conducted to identify their use of time in the care of these patients. PATIENTS: Children aged birth through 18 years meeting International Classification of Diseases, Ninth Revision, Clinical Modification criteria for chronic conditions. Patients with acute conditions were used as controls. INTERVENTION: A program of expanded care funded since 1989 by a regional insurance company. RESULTS: Between 1984 and 1995, mean length of stay for children with chronic conditions decreased from 83.9 to 10.6 days; mean annual admissions decreased from 2796 to 1622. Median hospital inpatient charges, adjusted for cost of living, decreased from $26.1 to $14.6 million. A $77.7 million savings occurred for inpatient care, with total expenditures from the insurance program of $3.6 million (a 21:1 ratio). Almost half the professional activities provided for these children were for services that could not be reimbursed in a fee-for-service model. Median adjusted inpatient charges were lower in Rochester, NY ($8746) than in other academic medical centers ($12773) or in a national survey of hospitals ($12462), and fewer children were readmitted within 30 days in Rochester (12.7%) than in other academic medical centers (15.0%). CONCLUSIONS: An investment of funds by a regional insurance company was associated with reduced costs, admissions, and lengths of stay for children with chronic conditions, and resulted in significant savings for the company. This model may be applicable to other centers.

Adolescent↗