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Biomedical subjects

D Y Fong

Publications and source records attributed to D Y Fong.

9 recordsLinked to original sources
PubMed2001

Modelling variation of lower leg length growth in early life.

We consider the estimation of sources of variation for panel data with repeated measurements. With no repeated measurements and known measurement error, models for variation decomposition have been proposed when there are one or more types of measurements. Estimation was performed using the EM algorithm accompanied by model augmentation that demands more computational efforts. In this article we extend previous variation models and modify the estimation methods in order to estimate various variation components after eliminating the unknown effects of measurement error. Specifically, methods that dispense with model augmentation and estimation of time-dependent covariates are considered. A set of lower leg length data from Chinese infants is analysed by using the proposed model. Interestingly, our results are consistent with the well-accepted three-phase (infancy-childhood-puberty) growth transition proposition for human growth. Moreover, gender effect is found to be time-varying.

Anthropometry↗
PubMed2001

Clinical features of 46 eyes with calcified hydrogel intraocular lenses.

PURPOSE: To clarify the clinical features of delayed calcification of hydrogel intraocular lenses (IOLs) based on observation of a large case series. SETTING: Ophthalmology department of 2 university teaching hospitals, Hong Kong, China. METHODS: The first 44 patients with a known diagnosis of calcified IOL were recruited. Medical and ophthalmic histories were obtained. Surgical details, surgical complications, and visual acuity before and after IOL implantation were also retrieved. Patients then had a visual acuity test, a slitlamp examination of the features of the IOL calcification, and a fundus examination for clarity of view. RESULTS: Forty-six eyes of 44 patients had IOL calcification. All had a Hydroview IOL. The onset was from 4 to 26 months after surgery. Ninety-three percent of eyes had generalized IOL calcification, and 96% had forceps marks on the IOL. Mean visual acuity deteriorated from 0.4 at 3 months to 0.13 at 19 months. Visual loss was more severe in patients with diabetes mellitus or ischemic heart disease and in those in which the IOL calcified earlier after implantation. CONCLUSION: All cases of IOL calcification were delayed in onset. The presence of forceps marks may provide a clue to the pathogenesis. Bilateral but asymmetric involvement in 2 patients suggests that the IOL was involved in the pathogenesis. Affected patients lost an average of 2.8 Snellen lines of visual acuity. Some eyes progressed more rapidly; however, the modulating factors remain unknown.

Aged↗
PubMed2001

Dynamic random effects models for times between repeated events.

We consider recurrent event data when the duration or gap times between successive event occurrences are of intrinsic interest. Subject heterogeneity not attributed to observed covariates is usually handled by random effects which result in an exchangeable correlation structure for the gap times of a subject. Recently, efforts have been put into relaxing this restriction to allow non-exchangeable correlation. Here we consider dynamic models where random effects can vary stochastically over the gap times. We extend the traditional Gaussian variance components models and evaluate a previously proposed proportional hazards model through a simulation study and some examples. Besides, semiparametric estimation of the proportional hazards models is considered. Both models are easily used. The Gaussian models are easily interpreted in terms of the variance structure. On the other hand, the proportional hazards models would be more appropriate in the context of survival analysis, particularly in the interpretation of the regression parameters. They can be sensitive to the choice of model for random effects but not to the choice of the baseline hazard function.

Animals↗
PubMed2001

Acupuncture for frozen shoulder.

This randomised controlled trial was undertaken to evaluate the effectiveness of acupuncture as a treatment for frozen shoulder. Thirty-five patients with a diagnosis of frozen shoulder were randomly allocated to an exercise group or an exercise plus acupuncture group and treated for a period of 6 weeks. Functional mobility, power, and pain were assessed by a blinded assessor using the Constant Shoulder Assessment, at baseline, 6 weeks and 20 weeks. Analysis was based on the intention-to-treat principle. Compared with the exercise group, the exercise plus acupuncture group experienced significantly greater improvement with treatment. Improvements in scores by 39.8% (standard deviation, 27.1) and 76.4% (55.0) were seen for the exercise and the exercise plus acupuncture groups, respectively at 6 weeks (P=0.048), and were sustained at the 20-week re-assessment (40.3% [26.7] and 77.2% [54.0], respectively; P=0.025). We conclude that the combination of acupuncture with shoulder exercise may offer effective treatment for frozen shoulder.

Acupuncture Therapy↗
PubMed2000

[A morphometric study on the microvessel in oral submucous fibrosis].

To investigate the pathologic change of the microvessel in oral submucous fibrosis(OSF), the pathologic buccal tissues of 27 patients with OSF were studied by using immunochemical method. Microvessel quantity(MVQ), quantity density(QD), microvessel area(MVA) and area density(AD) were determined by means of computer-aided image analysis system. The results showed the increase in MVQ and QD in the early stage and the decrease in MVQ, QD, MVA and AD in the middle stage and the late stage. The authors concluded that presence of microvessel hyperplasia occurred in the early stage of OSF.

Capillaries↗
PubMed2000

Risk factors of obesity in preschool children in China: a population-based case--control study.

OBJECTIVE: To identify the risk factors of obesity in preschool children in China. DESIGN: A nationwide case-control study in eight cities in China. SUBJECTS: A total of 748 boys and 574 girls (age 0.1 - 6.9 y), including the obese and non-obese. One obese child was matched with one non-obese child by sex and age. MEASUREMENTS: Weight, height and other measurements were taken for all the subjects. The information on child activity, feeding pattern and family background was collected by our study team from the parents and the kindergarten teacher. RESULTS: Birth weight > or =4.0 kg, high eating speed, obesity among the child's relatives > or =25%, mother's body mass index (BMI) > 25 kg/m2 and father's BMI > 25 kg/m2 were identified as the major significant (P < 0.05) risk factors of obesity in preschool children in China. CONCLUSION: Family history of obesity, high birth weight and eating speed were identified as the risk factors of obesity in preschool children in China. Our results show the need for family therapy as part of an intervention program for childhood obesity, which includes behavior modification.

Birth Weight↗
PubMed2000

Blood pressure is associated with body mass index in both normal and obese children.

Obesity is associated with elevated blood pressure (BP) both in adults and children. Childhood obesity has become a severe health problem, especially during the last few decades. So far there has not been any large-scale study specifically focusing on the association between obesity and BP in early life. The aim of this study is to examine systematically the association between obesity and BP in preschool Chinese children in mainland China. In 1996, measurements of weight, height, and BP values were collected in a nationwide, case-control study of 748 boys and 574 girls who ranged in age from 0.1 to 6.9 years in 8 cities in mainland China. One obese child and 1 nonobese child were matched for gender and age. The BP differences of the mean-matched pair were approximately 5 mm Hg for systolic blood pressure (SBP) and approximately 4 mm Hg for diastolic blood pressure (DBP) (P<0.05); a higher value was noted in obese children. The BP value of 19.4% children in the obese group and 7.0% children in the nonobese group was higher than the 95th percentile value (P<0.0001), which is defined as high BP by the Task Force on Blood Pressure Control in Children. Both SBP and DBP were significantly (P<0.05) positively related to body mass index (BMI) values (P<0.05) for children in obese and nonobese groups after adjustment for age, gender, and height. To be specific, an increase of 1 BMI unit was associated with, on average, an increase of 0.56 mm Hg and 0.54 mm Hg in SBP and DBP, respectively, for obese children. In nonobese children, the increase in SBP and DBP was 1.22 mm Hg and 1.20 mm Hg, respectively. An increase in the BMI is conclusively associated with elevated SBP and DBP in nonobese children. Furthermore, an increase in the adjusted BMI was associated with an increase in SBP and DBP in obese and nonobese children.

Blood Pressure↗
PubMedDate not supplied

State duration models in clinical and observational studies.

Many studies in medicine involve conditions whereby subjects make transitions among a set of defined states over time. In such situations the durations of sojourns in specific states is frequently of interest. This article considers the modelling and analysis of sojourn times, beginning with semi-Markov models in which the durations of different sojourns are independent, and then considering extended models incorporating chronological time effects and random effects. Methodologic challenges for inference are discussed, and examples involving a relapse-remitting process and recurrent events are considered.

Bronchitis↗