Biomedical subjects

Paul Mitchell

Publications and source records attributed to Paul Mitchell.

At least 163 records · Page 9Linked to original sources

PubMed2003

Patterns of glaucomatous visual field defects in an older population: the Blue Mountains Eye Study.

This report aims to describe the frequency of different patterns of visual field loss in open-angle glaucoma (OAG). The Blue Mountains Eye Study examined 3654 persons (aged 49+) during 1992-1994. Humphrey supra-threshold visual fields were performed in 88.9%. Those classified as glaucoma suspects had 30-2 full-threshold fields (9.2%). Of OAG cases (n = 108) with field tests in both eyes (n = 97), unilateral defects were present in 49 (50.5%) and bilateral in 48 (49.5%). Advanced field loss was found in 16 (15.4%) subjects and in 22 (10.9%) eyes, with bilateral loss present in 6 (6.2%) cases. Of all eyes of OAG cases (n = 201), 49 (24.4%) had no defects, 52 (25.9%) upper, 61 (30.3%) lower, and 17 (8.5%) had combined upper and lower loss. Of the upper and lower cases (n = 113), the types of defects included nasal step (36), arcuate (26), nasal plus arcuate (26), and hemispherical defects (25). Of subjects with fields in at least one eye (n = 104), there was a similar proportion in the worse eye of upper defects (28.8%), lower (31.7%), and combined upper and lower (24.0%). Undiagnosed OAG was more frequent in unilateral (65.3%) than bilateral (34.7%) cases (P = 0.003). This study reports the pattern of typical glaucomatous field loss in an older Australian population.

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PubMed2003

Computer-assisted retinal vessel measurement in an older population: correlation between right and left eyes.

This study assessed the correlation between computer-assisted retinal vessel measurements of right and left eyes, from subjects in a defined, community-based older population. Retinal photographs from participants in the Blue Mountains Eye Study were digitized. All retinal arterioles and venules located 0.5-1.0 disc diameters from the optic disc margin were identified and a computer program measured their diameters. Pearson correlation (R2) statistic was used to assess the correlation in a random subsample of 1546 images. Substantial correlation between right and left eye measurements was found for summary indices of retinal arterioles (R2 = 0.70) and venules (R2 = 0.77). Higher correlation was found for intragrader (R2 0.75-079) than for intergrader assessment (R2 0.67-0.72). Moderate correlation was found in arteriole-to-venule ratio assessed by the same (R2 = 0.57) or different (R2 = 0.52) graders. Measurements from one eye can thus adequately represent the retinal vessel diameters of a person.

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PubMed2003

Correlation between generalized and focal retinal arteriolar narrowing in an older population.

This study aimed to assess the associations between generalized and focal retinal arteriolar narrowing in the Blue Mountains Eye Study population (n = 3654 persons aged 49+ years). Summarized estimates of the average retinal arteriolar diameter, the central retinal arteriolar equivalent (CRAE) and arteriole-to-venule ratio were obtained from right eye photographs of each participant using a computer-assisted method. Focal retinal arteriolar narrowing was graded from retinal photographs of both eyes using a 'light-box' method. The proportion of subjects with focal arteriolar narrowing increased as CRAE decreased from the widest (2.2%) to the narrowest (7.8%) quintile (P for trend = 0.001). A receiver operating characteristic curve was constructed using CRAE to detect focal arteriolar narrowing. With the diagnostic cut point set at the 4th decile of CRAE, the sensitivity and specificity in detecting focal arteriolar narrowing were 64% and 61%,respectively. These data suggest a moderate correlation between generalized (CRAE) and focal arteriolar narrowing. However, no significant association was found between arteriole-to-venule ratio and focal arteriolar narrowing.

Arterioles↗

PubMed2003

Measurement of the economic impact of visual impairment from age-related macular degeneration in Australia.

The purpose of this report was to: (i) outline the potential value of health economic studies into age-related macular degeneration (AMD); (ii) provide an overview of health economic studies pertinent to AMD; and (iii) outline the basic frame work of cost-of-illness studies (a useful first step in applying economic methods). The detection and management of sensory loss in the elderly plays a key role in the Australian Government's Healthy Ageing Strategy. Age-related macular degeneration is currently the leading cause of blindness in elderly Australians. Although a large proportion of AMD cases remain untreatable, the introduction of photo-dynamic therapy provides a relatively expensive and possibly cost-effective innovation for others. Antioxidant therapy has also been proven effective in reducing progression of early to late disease. The discipline of economics can contribute to an understanding of AMD prevention and treatment through: (i) describing the current burden of disease; (ii) predicting the changes in the burden of disease over time, and (iii) evaluating the efficiency of different interventions. Cost-of-illness studies have been performed in many fields of medicine. Little work, however, has been done on describing the economic impact from AMD. A number of different economic evaluation methods can be used in judging the efficiency of possible interventions to reduce the disease burden of AMD. Although complementary in nature, each has specific uses and limitations. Studies of the economic impact of eye diseases are both feasible and necessary for informed health care decision-making.

Australia↗

PubMed2003

Visual risk factors for hip fracture in older people.

OBJECTIVES: To determine the association between poor vision and risk of hip fracture in the Blue Mountains Eye Study. DESIGN: Prospective population-based cohort study. SETTING: Two post code areas in the Blue Mountains, west of Sydney, Australia. PARTICIPANTS: Three thousand six hundred fifty-four community-dwelling Australians aged 49 and older. MEASUREMENTS: At baseline, subjects had an extensive eye examination, including refraction, contrast sensitivity and visual field testing, photographs of the lens and retina, and an interview. Hip fractures during the 5-year follow-up were identified by self-report and review of medical records and were radiologically confirmed. RESULTS: For 2-year follow-up (17 hip fractures), the adjusted hazard ratio (HR) for risk of hip fracture in those with corrected visual acuity worse than 20/60 was 8.4 (95% confidence interval (CI) = 1.5-48.5, population attributable risk (PAR) = 27%); for presence of posterior subcapsular cataract, the adjusted HR was 5.0 (95% CI = 1.1-23.0, PAR = 24%); and for visual field loss, the adjusted HR was 5.5 (95% CI = 1.0-29.8, PAR = 55%). In those aged 75 and older, visual acuity worse than 20/60 gave an adjusted HR of 40.6 (95% CI = 5.6-292.5, PAR = 49%). Visual impairment of any type did not predict risk of hip fracture after a 2-year follow-up. CONCLUSION: Visual impairment is strongly associated with risk of hip fracture in the next 2 years but not over a longer period of time.

Aged↗

PubMed2003

Visual impairment and nursing home placement in older Australians: the Blue Mountains Eye Study.

PURPOSE: To assess whether visual impairment at baseline is an independent contributor to subsequent nursing home placement during a 6-year follow-up. METHODS: 3654 non-institutionalised people aged 49+ years (82.4% of those eligible) who participated in baseline examinations of the Blue Mountains Eye Study (1992-94) were followed during 1997-99. Presenting visual acuity was measured with current glasses and a standardised refraction performed. We defined visual impairment as visual acuity reduced to <or=20/40. Permanent nursing home admissions during follow-up were confirmed by the regional Aged Care Assessment Team and government subsidy payment records. RESULTS: At baseline, 511 participants had presenting visual impairment. After refraction, vision improved to 20/30 or better in 346 persons (68%, "correctable"), while 165 (32%) remained visually impaired. During follow-up, 162 study participants (5.0%) were admitted permanently to a nursing home. The age-adjusted 6-year incidence was 3.6% for participants with normal vision, 16.2% for those with visual impairment after best correction and 8.1% for those with "correctable" visual impairment. After adjusting for non-cognitive factors that predicted nursing home placement, the relative risk (RR) for nursing home admission among persons with visual impairment after best correction was 1.8 (95% CI 1.1-2.9). A similar magnitude of association was found among persons with "correctable" visual impairment (RR 2.1, 95% CI 1.4-3.1). For each line of reduction in presenting visual acuity at baseline, there was a 7% increased risk of subsequent nursing home placement. CONCLUSIONS: This study suggests that decreased vision may be a marker or contributing factor to subsequent nursing home placement in general older populations.

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PubMed2003

Systemic use of anti-inflammatory medications and age-related maculopathy: the Blue Mountains Eye Study.

PURPOSE: To assess whether an association exists between systemic use of anti-inflammatory medications at baseline and the prevalence or incidence of either late or early age-related maculopathy (ARM) in a population-based cohort. METHODS: 3654 participants of the Blue Mountains Eye Study baseline examination (1992-94) were followed during 1997-99. Use of anti-inflammatory medication was recorded during the baseline interview. After excluding 543 persons who died since baseline, 2334 (75% of the surviving participants) attended 5-year follow-up examinations. Retinal photographs taken during both examinations were graded using the Wisconsin Age-Related Maculopathy Grading System. Prevalence refers to the proportion of participants having ARM at baseline. Incidence refers to the proportion of participants without ARM at baseline who developed it over the 5-year period. Known ARM risk factors were adjusted for when assessing the relationship between use of anti-inflammatory medications and ARM. RESULTS: At baseline, 1010 (27.6%) of 3654 participants were current users of non-steroidal anti-inflammatory drugs (NSAIDs), 514 (14.1%) were past users and 1282 (35.1%) were ever users. The corresponding numbers of subjects reporting current, past or ever use of corticosteroids (including inhaled steroids) were 225 (6.2%), 519 (14.2) and 564 (15.4), respectively. Late ARM was present in 72 participants (2.0%) and early ARM was present in 171 participants (4.9%) at the baseline examination. During the follow-up period, 25 participants (1.1%) developed incident late ARM and 192 (8.7%) developed incident early ARM. After adjusting for age, sex, family history of ARM and smoking, no significant associations were evident for the use of NSAIDs or corticosteroids and the prevalence of either late or early ARM. There were also no associations found between use of these medications at baseline and the 5-year incidence of either late or early ARM. CONCLUSIONS: No association was found between use of systemic anti-inflammatory medications and either the cross-sectional prevalence or longitudinal incidence of ARM in this population.

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PubMed2003

Causes of visual impairment in two older population cross-sections: the Blue Mountains Eye Study.

AIMS: To describe the causes of bilateral and unilateral blindness and visual impairment in two cross-sections of an older Australian population 6 years apart. METHODS: The Blue Mountains Eye Study examined 3654 persons aged 49-97 years during 1992-1994 (population cross-section 1). Cohort survivors (2335) and 1174 persons who moved to the area or reached an eligible age were examined during 1997-2000, a total of 3509 persons (population cross-section 2). LogMAR visual acuity was measured after standardized refraction. Blindness and visual impairment were respectively defined by visual acuity <6/60 and <6/12. Causes were determined for the two temporal cross-sections. RESULTS: Age-related macular degeneration (AMD) was the principal cause of bilateral and unilateral non-correctable blindness in both cross-sections. AMD caused 77% of bilateral blindness in Cross-section 1 and 50% in Cross-section 2. Cataract, glaucoma, corneal and neurological disease were next equally frequent causes (6% each) of bilateral blindness in Cross-section 1. In Cross-section 2, cataract ranked as the third most frequent principal cause (10%) after other retinal diseases (40%). The proportion of unilateral blindness with AMD as principal cause was very similar (around one-third of cases) in the two cross-sections; while in Cross-section 2 blindness was less frequently caused by cataract (19% vs. 13%). Cataract was the principal cause of both bilateral and unilateral visual impairment, responsible for 50% of bilateral (better eye) and 35-40% of unilateral (worse eye) impairment, with slightly lower rates found in Cross-section 2 than in Cross-section 1. AMD was consistently the second most frequent cause, causing one-third of bilateral and one-fifth of unilateral visual impairment. CONCLUSIONS: These data indicate a relative stable pattern of causes for blindness and visual impairment, with AMD and cataract, respectively, dominating these two levels.

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PubMed2003

Cardiovascular disease, vascular risk factors and the incidence of cataract and cataract surgery: the Blue Mountains Eye Study.

PURPOSE: To assess whether an association exists between cardiovascular disease, vascular risk factors and incident cataract and cataract surgery. METHODS: The Blue Mountains Eye Study examined 3654 participants > or = 49 years of age during 1992-4, then 2335 survivors (75.1%) after five years. Trained interviewers administered a vascular history questionnaire; height, weight and blood pressure were measured. Lens photographs from both examinations were graded for presence of cortical, nuclear or posterior subcapsular cataract. RESULTS: Obesity (body mass index > or = 30 kg/m2) was significantly associated with increased incidence of both cortical [odds ratio (OR) 1.6, 95% confidence interval (CI) 1.2-2.2] and posterior subcapsular cataract (OR 2.1, CI 1.2-3.7). Hypertensive participants using medication and aged less than 65 years at baseline had a higher incidence of posterior subcapsular cataract (OR 3.4, 95% CI 1.3-8.4) than normotensive subjects. A history of angina was associated with higher cataract surgery incidence (OR 2.1, 95% CI 1.3-3-5). CONCLUSIONS: These longitudinal data provide some evidence supporting a relationship between cardiovascular disease, vascular risk factors and incident cataract and cataract surgery. The findings confirm a number of associations previously documented in cross-sectional data.

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PubMed2003

Myopic refractive shift caused by incident cataract: the Blue Mountains Eye Study.

PURPOSE: To assess the myopic shift in refraction caused by incident cataract in the Blue Mountains Eye Study (BMES) population. METHODS: Five-year prospective follow-up of the BMES, initially performed in 1992. After 5 years, 2335 survivors (75.1%) of 3654 baseline BMES participants were re-examined. Refractive change was assessed by age, sex, incident cataract type and baseline refraction. Slit-lamp and retroillumination lens photographs were graded for presence of incident cataract and signs of previous cataract surgery. Objective and subjective refractions were performed. RESULTS: In a multivariate model, age (p < 0.0001), incident nuclear cataract (p < 0.0003), hyperopia (p < 0.0009), incident posterior subcapsular cataract (p < 0.0027) and incident cortical cataract (p < 0.025) were factors associated with a relatively modest myopic refractive shift (0.34 diopters). Baseline myopia and gender were not associated with refractive change over the follow-up period. A myopic shift in refraction occurred most frequently in older (> or = 70 years) than younger (< 70 years) participants. CONCLUSIONS: Older age, baseline hyperopia and all types of incident cataract were principal factors found associated with myopic refractive shift over 5 years in an older population.

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PubMed2003

Asteroid hyalosis in an older population: the Blue Mountains Eye Study.

PURPOSE: To assess the prevalence of and associations with asteroid hyalosis in an older population. METHODS: The Blue Mountains Eye Study was a cross-sectional study of an older community (aged 49-97 years). Subjects included were those attending the baseline (n = 3654) and 5-year examinations (n = 2335) of this cohort. Asteroid hyalosis was diagnosed clinically by the presence of cream-white spherical bodies within the vitreous or from grading of stereo retinal photographs of both eyes. Logistic regression assessed age-sex adjusted associations with relevant characteristics, including diabetes and cardiovascular variables. RESULTS: Asteroid hyalosis was found in 36 subjects (1.0%), 95% confidence interval (CI) 0.7% to 1.3%, and was bilateral in three affected subjects (8.3%). An age-related increase in prevalence was observed, increasing from 0% of persons aged less than 55 years to 2.1% of persons aged 75 years or older. The prevalence of this sign was significantly higher in men (1.4%) than in women (0.6%), the age-adjusted odds ratio (OR) was 2.54 (CI 1.25-5.16). No statistically significant associations were found between asteroid hyalosis and a history of heart disease, gout, current smoking, the highest level of alcohol consumption or with presence of diabetes (diagnosed from history or fasting blood glucose tests). CONCLUSIONS: Asteroid hyalosis was detected in 1% of participants in this Australian older population. No significant associations were found, apart from age and male gender. Our study provides similar age-specific prevalence data to a recent report from the Beaver Dam Eye Study for asteroid hyalosis.

Age Distribution↗

PubMed2003

Does smoking affect intraocular pressure? Findings from the Blue Mountains Eye Study.

PURPOSE: To assess the relationship between smoking and intraocular pressure. MATERIALS AND METHODS: The Blue Mountains Eye Study examined 3654 residents aged 49 years and older in an area west of Sydney, Australia from 1992 to 1994. A trained interviewer collected a detailed history of smoking. Intraocular pressure was measured using Goldmann applanation tonometry; as the correlation between right and left eyes was very high, only right-eye data are presented. Participants using glaucoma medications or who had evidence of previous cataract surgery were excluded. RESULTS: Current smokers (15.8% of participants) had slightly higher mean intraocular pressures (16.34 mm Hg) than nonsmokers (16.04 mm Hg). Intraocular pressure (in the right eye) was significantly associated with current smoking, after adjusting for age and sex (P = 0.03). This association remained unchanged after simultaneous adjustment for other variables associated with intraocular pressure, including blood pressure, diabetes, myopia, glaucoma, family history, and pseudoexfoliation (P = 0.02). CONCLUSIONS: This study identified a modest cross-sectional positive association between current smoking and intraocular pressure.

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PubMed2003

Risk factors for tinnitus in a population of older adults: the blue mountains hearing study.

OBJECTIVE: To identify potential and modifiable risk factors for tinnitus in a population of older adults. STUDY DESIGN: Cross-sectional study. Detailed questionnaires were interviewer-administered in a representative sample of 2015 persons aged 55+ yr, living in an area west of Sydney, Australia. Air- and bone-conduction audiometric thresholds were measured from 250 to 8000 Hz and from 500 to 4000 Hz, respectively. TEOAE and SOAE were measured for both ears. RESULTS: After adjusting for multiple variables in a Cox proportional hazards model, factors that significantly increased the risk of tinnitus were poorer hearing and cochlear function, self-reported work-related noise exposure, and history of middle ear or sinus infections, severe neck injury or migraine. CONCLUSION: Interventions aimed at reducing age-related hearing loss, particularly by reducing excessive work-related noise exposure, and the effective, timely treatment of ear-related infections, may all decrease the risk of tinnitus.

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PubMed2003

Relationships between age, blood pressure, and retinal vessel diameters in an older population.

PURPOSE: To describe the cross-sectional relationships between age, blood pressure (BP), and quantitative measures of retinal vessel diameters in an older Australian population. METHODS: Retinal photographs from right eyes of participants (n = 3654, aged 49+ years) in the Blue Mountains Eye study taken during baseline examinations (1992-1994) were digitized. The width of all retinal vessels located 0.5 to 1.0 disc diameters from the disc margin was measured by a computer-assisted method. Summarized estimates for central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) represent average retinal vessel diameters. The arteriole-to-venule ratio (AVR) was calculated. Associations between age and BP and CRAE, CRVE, and AVR were assessed with generalized linear models. RESULTS: Retinal vessel diameters decreased with increasing age in both men and women. CRAE and CRVE decreased by 4.8 microm and 4.1 microm, respectively, per decade increase in age, after adjusting for sex and mean arterial blood pressure. Mean AVR declined by 0.01 for each increasing decade of age, until 79 years. After adjustment for age, sex, smoking, and body mass index, CRAE, CRVE and AVR were all significantly and inversely associated with BP. For every 10-mm Hg increase in mean arterial blood pressure, AVR decreased by 0.012 and CRAE and CRVE decreased by 3.5 microm and 0.96 microm, respectively. CONCLUSIONS: Retinal arteriolar and venular diameters narrow with increasing age, and these parameters are inversely related to BP, independent of age, gender, and smoking. The findings are consistent with those from the Atherosclerosis Risk in Communities Study suggesting that decreased retinal vessel diameters may reflect microvascular damage from elevated blood pressure.

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PubMed2003

How the CATCH eat smart program helps implement the USDA regulations in school cafeterias.

This article describes the implementation of the U.S. Department of Agriculture's National School Lunch Program (NSLP) standards in school lunch menus in 56 intervention and 20 control schools from the Child and Adolescent Trial for Cardiovascular Health (CATCH) 5 years after the main trial, compared with 12 schools previously unexposed to CATCH. School food service personnel completed questionnaires to assess CATCH guideline implementation, demographic data, behavioral constructs, training, program material use, and participation in competing programs. Five days of menus and recipes were collected from school cafeteria staff, averaged, and compared to USDA School Meal Initiative (SMI) standards. Significant differences between intervention and unexposed schools were found for training and knowledge of CATCH and in mean percentage energy from fat and carbohydrates. Intervention schools most closely met USDA SMI recommendations for fat. Thus, the CATCH Eat Smart Program assisted school cafeterias in meeting USDA guidelines 5 years postimplementation.

Adolescent↗

PubMed2003

Prevalence and characteristics of tinnitus in older adults: the Blue Mountains Hearing Study.

There have been few recent estimates of the prevalence of tinnitus from large population-based samples of older persons. Our study aimed to assess the prevalence and characteristics of prolonged tinnitus in a representative sample of 2015 adults aged 55-99 years, residing in the Blue Mountains, west of Sydney, Australia, during 1997-99. All participants underwent a detailed hearing examination by an audiologist, including comprehensive questions about hearing. After age adjustment, subjects reporting tinnitus had significantly worse hearing at both lower and higher frequencies (p < 0.001). This difference was more marked in younger than in older subjects (p < 0.05). Overall, 602 subjects (30.3%) reported having experienced tinnitus, with 48% reporting symptoms in both ears. Tinnitus had been present for at least 6 years in 50% of cases, and most (55%) reported a gradual onset. Despite tinnitus being described as mildly to extremely annoying by 67%, only 37% had sought professional help, and only 6% had received any treatment.

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PubMed2003

A Phase I dose-escalation study of sibrotuzumab in patients with advanced or metastatic fibroblast activation protein-positive cancer.

PURPOSE: The purpose of this research was to determine the safety, immunogenicity, pharmacokinetics, biodistribution, and tumor uptake of repeat infusions of a complementarity-determining region grafted humanized antibody (sibrotuzumab) directed against human fibroblast activation protein (FAP). EXPERIMENTAL DESIGN: A Phase I open-label dose escalation study was conducted in patients with cancers epidemiologically known to be FAP positive. Patients were entered into one of four dosage tiers of 5, 10, 25, or 50 mg/m(2) sibrotuzumab, administered weekly for 12 weeks, with trace labeling with 8-10 mCi of (131)I in weeks 1, 5, and 9. RESULTS: A total of 26 patients were entered into the trial (15 males and 11 females; mean age, 59.9 years; age range, 41-81 years). Twenty patients had colorectal carcinoma, and 6 patients had non-small cell lung cancer. A total of 218 infusions of sibrotuzumab were administered during the first 12 weeks of the study, with 24 patients being evaluable. One patient received an additional 96 infusions on continued-use phase for a total of 108 infusions over a 2-year period, and 1 patient received an additional 6 infusions on continued use. There were no objective tumor responses. Only one episode of dose-limiting toxicity was observed. Therefore, a maximum tolerated dose was not reached. Treatment-related adverse events were observed in 6 patients during the infusional monitoring period. Four of the 6 patients, 3 of whom had associated positive serum human antihuman antibody, were removed from the study because of clinical immune responses. Gamma camera images of [(131)I]sibrotuzumab demonstrated no normal organ uptake of sibrotuzumab, with tumor uptake evident within 24-48 h after infusion. Analysis of pharmacokinetics demonstrated a similar mean terminal t(1/2) of 1.4-2.6 days at the 5, 10, and 25 mg/m(2) dose levels, and with a longer mean t(1/2) of 4.9 days at the 50 mg/m(2) dose level. CONCLUSION: Repeat infusions of the humanized anti-FAP antibody sibrotuzumab can be administered safely to patients with advanced FAP-positive cancer.

Adult↗

PubMed2003

Training GPs to screen for diabetic retinopathy. The impact of short term intensive education.

OBJECTIVE: To improve general practitioners' knowledge and skills about diabetic retinopathy. SETTING: An upskilling program of 11 Sydney (New South Wales) GPs. MAIN OUTCOME MEASURES: Level of competency determined by an educational assessment before and six weeks after the program. RESULTS: Mean scores for multichoice questions increased from 53% before the education to 84% after (p < 0.001); for a photographic examination from 44 to 53% (p = 0.08); and for clinical examination from 41 to 69% (p < 0.001). The screening specificity increased from 47 to 73%. CONCLUSION: General practitioners' knowledge and skills about diabetic retinopathy improved at least short term following an intensive educational program.

Clinical Competence↗