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R J Wilks

Publications and source records attributed to R J Wilks.

At least 19 recordsLinked to original sources
PubMed2006

Improvements in dose homogeneity for tangential breast fields from a selection of combinations of library compensators.

Individually paired physical compensators are used in our centre to improve dose homogeneity for radiotherapy to the whole breast. This technical note describes the further improvements that may be achieved when all possible combinations of individual compensators within the library are considered. A retrospective study of 78 patients using a total of 16 (left-sided) and 14 (right-sided) sets of library compensators was evaluated, and the results expressed in terms of the standard deviation of the differential dose-volume histogram and the dose range within the breast volume. The mean of the standard deviations was 3.17% (uncompensated), 2.16% (paired compensators) and 1.97% (combinations) and the mean homogeneity was 15.3%, 11.8% and 11.1%, respectively.

Breast Neoplasms↗
PubMed2005

Cold-induced elevation of forearm vascular resistance is inversely related to birth weight.

Fetal growth retardation has been linked to elevated blood pressure in adult life. This association between birth weight and blood pressure is present in childhood and is amplified with age. However, the mechanisms that underlie this association are largely unknown. We examined the relationship between birth weight and forearm vascular resistance and forearm blood flow in children aged 9-12.7 years. A total of 58 children were randomly selected from a cohort of 1610 born at the University Hospital of the West Indies in Jamaica where adequate antenatal and delivery records were available. Blood pressure, heart rate and forearm blood flow (by venous occlusion plethysmography) were measured at rest and after cold pressor and mental arithmetic tests. There was a significant inverse correlation between birth weight and the change in the vascular resistance for the cold pressor test (r=-0.47; P<0.001) and the mental arithmetic stress test (r=-0.26; P=0.05). The log ratio of vascular resistance under stress to resting decreased by 0.289 units per kg of birth weight (95% CI: 0.145-0.434; P=0.0002). Lower birth weight is associated with increased vascular responsiveness. Increased vascular resistance might be one mechanism linking fetal growth to subsequent elevated blood pressure.

Birth Weight↗
PubMed2005

High risk health behaviours among adult Jamaicans.

The purpose of this study was to assess the prevalence of high risk health behaviours among adult Jamaicans aged 15-49 years in 2000, and to compare the results with the 1993 survey. A nationally representative sample of 2013 persons aged 15-74 years was surveyed in 2000 using cluster sampling in the Jamaica Healthy Lifestyle Survey (Wilks et al, unpublished). Interviewer administered questionnaires and anthropometrical measurements were done. Data for a sub-sample of adults aged 15-49 years were analyzed The sub-sample included 1401 persons (473 men and 928 women). Significantly more men (18.6%) than women (4.3%) reported never having had a blood pressure check (p = 0.0001). Approximately one-third of the women reported that they had never had a Pap smear (36.0%) or a breast examination (31.2%). Current cigarette smoking was reported in 28.6% of men and 7.7% of women (OR 3.73 CI 2.71, 5.15), while 49.0% of men and 15.0% of women ever smoked marijuana (OR 3.28 CI 2.56, 4.20). Significantly more men (28.0%) than women (11.7%) reported ever having a sexually transmitted disease (OR 2.93 CI 2.16, 3.97); having more than one sexual partner in the past year (49.1% vs 11.4%, OR 4.31 CI 3.22, 5.76) and usually using a condom during sexual intercourse (55.3% vs 40.5%, OR 1.3 CI 1.11, 1.68). Between 1993 and 2000, significant trends include: more persons reported having a blood pressure check, a reduction in multiple sexual partners, increased condom use at last sex (women), reduced crack/cocaine use (males) and increased marijuana smoking. Although there were some significant positive lifestyle trends between 1993 and 2000, high risk behaviours remain common among Jamaican adults. Comprehensive health promotion programmes are needed to address these risk behaviours.

Adolescent↗
PubMed2004

Energetic determinants of glucose tolerance status in Jamaican adults.

As type 2 diabetes mellitus (DM2), obesity and sedentary lifestyles are increasing in developing countries, this observational study investigated the role of physical activity on DM2 in Jamaica. Anthropometry, body composition (by bioelectrical impedance analysis) and glucose tolerance status was assessed in 722 adults in 1993 and 1997. Energy expenditure was estimated in a subset using measured resting energy expenditure in combination with self-reported activity recalls. The rates of impaired glucose tolerance (IGT) were 23.7 and 27.3%, and DM2 were 16.3 and 23.7% among men and women, respectively. After adjusting for body composition, a one-unit increase in physical activity significantly reduced the odds of having diabetes (OR = 0.05; 95% CI: 0.004, 0.66), but not IGT. Hence, decreased physical activity is a significant independent contributor to the high rates of glucose intolerance in Jamaica. Efforts must be directed at minimizing obesity and increasing physical activity in developing countries.

Adult↗
PubMed2004

Comparison of a lung fitting algorithm with CT data for tangential fields in radiotherapy of the breast.

A method of estimating the shape and position of the lung in tangential breast fields is presented for patients who have not been CT scanned. Using the Osiris system, the external contour is obtained optically, and an estimated lung structure superimposed on the transverse outlines based on the measured lung depth in the tangential fields and an analysis of the typical lung shapes obtained from CT images. The accuracy of this fit was determined by comparison with a set of 64 CT images imported into the Osiris system. Dose distributions were calculated by two treatment planning systems: ADAC Pinnacle and GE Target2. The computed dose distributions for 6 MV photons were compared against measured doses in a specialized breast phantom. For the worst case of lung fit compared with CT, the dosimetric error (based upon ADAC Pinnacle calculations) was 2.0% in the shadow of the lung. For the complete patient data set, the relative dose errors to these points were reduced from a mean value of 8.4% and standard deviation (SD)=1.8% (no lung correction) to a mean of 0.2% and SD=1.0% (lung correction using fitted lung). It was also found that for every 1 cm of lung path length the dose to the breast along that path length increased by approximately 1%. The results of these investigations indicated that the lung fit model was satisfactory for routine clinical use, so that good dosimetric results can be obtained using lung correction without the need for CT imaging.

Algorithms↗
PubMed2004

Features of isolated post-challenge hyperglycaemia in Jamaican adults.

Isolated post-challenge hyperglycaemia (IPH) can be defined as a two-hour plasma glucose concentration > or = 11.1 mmol/L with a fasting plasma glucose concentration < 7.0 mmol/L. The aim of this prospective study was to determine the prevalence of IPH in a cohort of Jamaican individuals, and to determine if simple clinical features may predict the presence and subsequent diagnosis of IPH. A cohort of 1694 adults aged 25-74 years without physician-diagnosed diabetes mellitus was randomly selected. An oral glucose tolerance test (OGTT) was performed. Anthropometry, blood pressure and lipid profiles were measured. The prevalence of undiagnosed diabetes mellitus by the 1999 World Health Organization criteria was 6.4%. IPH accounted for 24% of these cases and 1.4% of the entire population. Individuals with IPH were significantly older, with greater body mass index, waist-hip ratio, systolic blood pressure, fasting blood glucose, total cholesterol and LDL-cholesterol than individuals with normal glucose tolerance. Individuals with IPH were not significantly different from individuals with fasting plasma glucose levels > or = 7 mmol/L (i.e. fasting hyperglycaemia) in anthropometry or blood pressure. However, total cholesterol and LDL-C were significantly elevated in the IPH group. OGTT screening of individuals with impaired fasting glucose (i.e. 6.1-6.9 mmol/l) could reduce the IPH group by 50%. Reducing the threshold for fasting glucose to 5.6 mmol/L would correctly classify 87% of the population. We concluded that individuals with IPH have features of the metabolic syndrome, which can aid in selection for screening. OGTT screening of individuals with fasting glucose values of 5.6-6.9 mmol/l is needed to identify IPH.

Adult↗
PubMed2004

Falls: A modifiable risk factor for the occurrence of hip fractures in the elderly.

The objective of the study was to examine the clinical and demographic features of patients with hip fractures presenting to the Accident and Emergency Department, the University Hospital of the West Indies (UHWI). The study involved all patients with hip fractures registered in the Trauma Registry at the UHWI between January 1, 1998 and December 31, 2001. They were assessed retrospectively for age, gender, associated extrinsic and intrinsic factors, cause of the fall, location when fracture occurred and the site of the femur that was fractured. One hundred and fifty-two persons were identified There were one hundred and eleven women and forty-one men. Seventy-eight per cent of the falls occurred in the over sixty-five-year age group. Ninety per cent of the patients had a fall associated with their fracture. Most of the falls occurred at the patients' homes. This study indicated that falling at home was the commonest associated factor for the occurrence of hip fractures and preventive measures may lead to reductions in the frequency of hip fractures seen in the emergency room.

Accidental Falls↗
PubMed2001

Anticardiolipin antibodies and risk of thromboembolic disease in young Jamaican women.

BACKGROUND: Anticardiolipin antibodies (aCL) are a heterogeneous group of antiphospholipid antibodies that are associated with arterial and venous thrombosis. We measured aCL in women, aged 15-49 years, to determine if they are an independent risk factor for thromboembolic disease. STUDY DESIGN: Case--control study METHODS: Fifty cases were studied including venous thromboembolism (n=29), stroke and myocardial infarction (n=21), along with 148 age-matched controls. Serum samples were assayed for aCL and anti-beta2 glycoprotein 1 antibodies using the enzyme-linked immunosorbent assay (ELISA). Information on other risk factors was obtained by a standardized questionnaire. RESULTS: aCL were present in 16/50 (32%) of cases compared with 25/148 (17%) of controls (P[?]=[?]0.02). Unadjusted odds ratio (OR) and 95% confidence interval (95% CI) for thromboembolic disease associated with aCL was 2.32 (1.10--4.87). Other risk factors were hypertension, 2.93 (1.20--7.17) and a history of other heart diseases, 12.78 (1.32--123.60). Adjustment for hypertension, diabetes, oral contraceptive use, smoking, alcohol use, varicose veins, a family history of cardiovascular disease and a history of other heart diseases yielded OR (95%CI) 2.99 (1.32--6.80). beta2 glycoprotein 1-dependent aCL were also an independent risk factor, OR 4.56 (1.76--17.83). Subgroup analysis was carried out separately for cases of MI and stroke and for venous thrombosis. Adjusted OR (95% CI) associated with aCL in cases of MI and stroke was 1.76 (0.46--6.73) and 3.32 (1.15--9.54) for venous thromboembolism. CONCLUSION: aCL are a risk factor for thromboembolic disease in young Jamaican women. They confer a strong independent risk for venous thromboembolism.

Adolescent↗
PubMed2001

Management of diabetes mellitus in three settings in Jamaica.

OBJECTIVES: To evaluate the quality of diabetic care in three clinics (one of them private and the other two public) in Jamaica, which is a middle-income country with a high prevalence (13%) of diabetes. METHODS: During a six-week census in 1995 at the three clinics we collected data retrospectively on a total of 437 diabetic patients. One of the clinics was a specialist public-hospital clinic ("SPMC"), one was a private group general practice ("PRMC"), and one was a public polyclinic ("PUBMC"). The patients' median age ranged from 56 years at SPMC and PRMC to 63 years at PUBMC. Median follow-up had been 6.0 years at SPMC, 9.2 years at PRMC, and 6.3 years at PUBMC. RESULTS: Fewer than 10% of the patients were controlled with diet alone. Insulin was the most commonly prescribed agent at SPMC (46%), compared to 7% each at the two other clinics. Sulfonylurea drugs alone or in combination with metformin were the most common agents at PUBMC and PRMC. Overall, 40% of the patients had satisfactory blood glucose control (< 8 mmol/L fasting or < 10 mmol/L postprandial). There was no significant difference among the clinics in the proportion of patients with satisfactory blood glucose control (P = 0.26). A blood glucose measurement had been recorded in the preceding year in 84% of the patients at SPMC, 79% at PRMC, and 67% at PUBMC. Glycosylated hemoglobin was infrequently measured: 16% at SPMC, 10% at PRMC, and 0% at PUBMC. Overall, 96% of patients had had surveillance for hypertension, and 81% had had surveillance for proteinuria. Surveillance for foot and retinal complications was generally infrequent and had been noted in patients' clinic records most commonly at SPMC (14% for foot complications, and 13% for retinal complications). The staff at the three clinics seldom advised the diabetic patients on diet, exercise, and other nonpharmacological measures, according to the clinics' records. CONCLUSIONS: The management of diabetes in Jamaica fell short of international guidelines. Our results also indicate the need to better sensitize health care professionals to these standards in order to reduce the burden of diabetes.

Adult↗
PubMed2001

Chronic diseases--facing a public health challenge.

Middle income countries like those in the Caribbean can feel proud of their achievements in health care. There has been a dramatic fall-off in infant mortality and crude mortality rates along with significant improvements in life expectancy at birth. However, these countries now find themselves grappling with the burden of chronic non-communicable diseases such as heart disease, stroke, hypertension, diabetes mellitus and cancer. There are good data to support the view that some of these diseases, in particular diabetes mellitus, have assumed epidemic proportions and there is concern that this fact may have been missed by many because of the surreptitious onset, as is the nature of the chronic diseases. The impact of this epidemic may have suffered because of the higher profile of more topical issues like HIV/AIDS even though the former makes a larger contribution to morbidity and mortality statistics. It is now obvious that despite the impact of other factors, lifestyle changes are the major contributors to the epidemic. In populations of similar genetic stock, living in significantly different socio-economic circumstances, the impact of increased dietary salt, increasing obesity and decreased physical activity on the prevalence of hypertension, diabetes mellitus and lipid disorders is unequivocal. Data from the developed world, which has already been through this epidemic of chronic diseases, have shown that increasing technological advances in medical care is an inefficient way to respond to the situation. A multi-sectoral approach is required to tackle this epidemic, including the provision of incentives for healthy eating and widespread opportunities for increased exercise and other physical activities. Continued research into the evolution of the epidemic, including reliable estimates via surveillance methods is a necessary component of our response. The problems and the solutions are not only the responsibilities of the health officials but must involve education, agriculture and other sectors of the economy.

Caribbean Region↗
PubMed2000

An optical method of estimating the relative output of a superficial unit for small applicators.

The uncertainties associated with the measurement of the radiation output from a superficial x-ray unit are increased when using small applicators, as discussed in the text. The method described here uses two stages to measure the relative outputs: the first stage uses a large-diameter flat chamber to measure the radiation integrated over the applicator end, and the second stage uses an optical imaging system to investigate the shape of the beam. These are combined to produce a relative output for each applicator, which may then be transformed to an absolute output by applying the relative factors to a direct measurement of absolute output on one of the larger applicators.

Biophysical Phenomena↗
PubMed2000

Blood pressure is related to placental volume and birth weight.

The objective of this study was to determine whether maternal nutrition and fetal and placental size program blood pressure. A longitudinal study linking the maternal anthropometric measurements of the first antenatal visit, ultrasound data of placental and fetal size, anthropometry at birth, and childhood growth and blood pressure was performed. The subjects were 428 women who attended the antenatal clinic at the University Hospital of the West Indies, Kingston, Jamaica, and their children, who were subsequently followed up. Systolic blood pressure at ages 1, 2, 2.5, 3, and 3.5 years was the main outcome measure. Pooling the data across ages, systolic blood pressure fell by 1.4 mm Hg for every 1-kg increase in birth weight (95% CI 0.2 to 2.7, P=0.02) and by 1.2 mm Hg for every 100-mL increase in placental volume at 20 weeks of gestation (95% CI 0.4 to 2.0, P=0.004). Blood pressure was also negatively associated with placental volume at 17 weeks and fetal abdominal circumference at 20 weeks. Measures of maternal nutritional status were strongly related to birth weight and placental volume but not directly to childhood blood pressure at these young ages. In conclusion, blood pressure is associated with fetal size in this population, as previously described among Europeans. We found associations between placental volume and abdominal circumference in the second trimester and childhood blood pressure, suggesting that the initiating events of blood pressure programming occur early in pregnancy. Measures of maternal nutritional status were not directly related to childhood blood pressure at these young ages but were strong predictors of both birth weight and placental volume, suggesting an indirect relation.

Adolescent↗
PubMed1999

Quantitative proviral DNA and antibody levels in the natural history of HTLV-I infection.

The pathogenesis of human T-cell lymphotropic virus type I (HTLV-I) in adult T-cell leukemia/lymphoma (ATL) and HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) is poorly understood. We prospectively followed up and evaluated the virologic correlates of infection in transfusion recipients after seroconversion, in asymptomatic carriers, and in ATL and HAM/TSP patients. Proviral DNA levels (copies/105 lymphocytes) were determined by real-time automated polymerase chain reaction and antibody titers by end-point dilution by use of an HTLV-I enzyme-linked immunoassay. In early infection, proviral load was initially elevated (median, 212 copies/105 lymphocytes at time 1) and later decreased (median, 99 copies at time 2, and 27 copies at time 3). Corresponding antibody titers were low at time 1 (1:2154), had significantly increased by time 2 (1:12312), and were stable by time 3 (1:4694). These viral markers were significantly lower in asymptomatic carriers than in HAM/TSP or ATL patients. Therefore, proviral load and antibody titers may be useful as predictive markers of disease among carriers.

Adolescent↗
PubMed1999

Blood pressure in Jamaican children: relationship to body size and composition.

Blood pressure levels in adults and children are related to body size and composition, but some of these relationships are unclear and they have been incompletely described in the Jamaican population. In a cross-sectional survey of 2,332 school children (6-16 years old; 1,046 boys, 1,286 girls), we measured systolic and diastolic blood pressure and pulse rate, and explored their relationship to weight, height, and waist, hip and mid-upper arm circumferences. The effect of these and other derived measures of body composition on blood pressure was explored in univariate and multivariate analysis. Blood pressure increased with age in both boys and girls, although the increase was greater for systolic than for diastolic blood pressure. The increase of systolic blood pressure among boys continued after age 11 years, but that for girls levelled off. Height and weight were the major predictors of blood pressure, but were highly correlated with each other and with all measures of body composition. Age, height and height-sex interaction explained 11.4% of systolic blood pressure variation, and the largest incremental contribution to this model was provided by the addition of body mass index or hip circumference, each explaining an additional 2.6% of the variance. Lean body mass made a larger contribution to blood pressure than percent fatness. Blood pressure in Jamaican children rises with age and this rise may be steeper in boys than girls. Blood pressure variation is significantly related to several measures of body composition including measures of fatness and fat free mass.

Adipose Tissue↗
PubMed1997

Relationship between maternal nutritional status and infant's weight and body proportions at birth.

OBJECTIVES: To examine maternal nutritional status and its relationship to infant weight and body proportions. DESIGN: Retrospective study of births from January-December 1990. SETTING: University Hospital of the West Indies, Jamaica. SUBJECTS: Records for 2394 live, singleton births, between 200-305 d gestation. MAIN OUTCOME MEASURES: Birth weight, crown heel length, head circumference, ponderal index, head circumference:length ratio, placental weight, placental:birth weight ratio. RESULTS: Mothers who were lighter had babies who had lower birth weight, were shorter, had smaller heads and had a higher HC:L ratio. Shorter and thinner women had babies who had lower birth weights, were shorter, had smaller heads and lighter placentas. Thinner women also had babies with a lower placental:birth weight ratio, and their BMI's were not linearly related to ponderal index and HC:L ratio. Women whose first trimester Hb levels were < 9.5 g/dl had babies with the lowest birth weight, crown heel length, placental weight and ponderal index. These measurements increased as the Hb levels rose to 12.5 g/dl but then fell at Hb levels > 12.5 g/dl. In the second and third trimester Hb levels were negatively associated with birth weight, crown heel length, head circumference, placenta weight and ponderal index. CONCLUSIONS: The data support the hypothesis that poor maternal nutrition is associated with foetal growth restraint. Poor maternal nutrition as indicated by low weight, height, and BMI are associated with smaller, shorter babies with smaller heads. Haemoglobin levels > 12.5 g/dl in pregnancy are associated with lighter, shorter, thinner babies, with smaller heads.

Adolescent↗