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Biomedical subjects

J D Willms

Publications and source records attributed to J D Willms.

6 recordsLinked to original sources
PubMed2002

Temporal trends in overweight and obesity in Canada, 1981-1996.

OBJECTIVE: To assess changes in the prevalence of overweight and obesity among Canadian children and adults between 1981 and 1996 using recent recommendations for the classification of overweight and obesity. DESIGN: Epidemiological study comparing the prevalence of overweight and obesity from the 1981 Canada Fitness Survey (CFS) to the 1996 National Longitudinal Survey of Children and Youth (NLSCY) and the 1996 National Population Health Survey (NPHS). SUBJECTS: Adults 20-64 y of age and children 7-13 y of age from the CFS, NLSCY and NPHS. MEASUREMENTS: BMI was calculated from directly measured or self-reported body mass and height. For adults 20-64 y of age, overweight and obesity were defined as BMI > or = 25 kg/m2 and BMI > or = 30 kg/m2, respectively. Age- and sex-specific cut-off points for children that correspond to the adulthood categories were used to define overweight and obesity for children 7-13 y of age. RESULTS: The prevalence of overweight increased from 48 to 57% among men and from 30 to 35% among women, while the prevalence of obesity increased from 9 to 14% in men and from 8 to 12% in women. The corresponding increases were from 11 to 33% in boys and from 13 to 27% in girls for overweight and from 2 to 10% in boys and from 2 to 9% in girls for obesity. CONCLUSION: The results indicate dramatic increases in the prevalence of both overweight and obesity in Canada over the last 15 y, and the problem is particularly pronounced among children.

Adolescent↗
PubMed2001

Preliminary evaluation of a video questionnaire to assess activity levels of children.

PURPOSE: The purpose of this study was to explore the validity of the Assessment of Young Children's Activity Using Video Technology (ACTIVITY) self-report instrument in assessing previous-day physical activity. METHODS: Forty-seven third-grade children (mean age 7.72 +/- 0.45, 41% female) from one elementary school completed the ACTIVITY on one weekday. To evaluate concurrent validity, children wore a Caltrac accelerometer and a Polar Vantage XL heart rate monitor on the day before completing the ACTIVITY. An ACTIVITY score from six time-anchored questions was obtained from the ACTIVITY. Mean Caltrac counts per minute (CNTSMIN), average activity heart rates, and cumulative minutes at or above 50% of heart rate reserve (50% HRR) were calculated for the entire day (7:00 a.m. to 7:00 p.m.). RESULTS: Significant Pearson product-moment correlations were observed between the ACTIVITY score and CNTSMIN (r = 0.40, P < 0.001) and 50% HRR (r = 0.50, P < 0.001). Answers from four of six time-anchored questions correlated significantly with heart rate scores during those time periods (r = 0.30-0.49). CONCLUSIONS: This exploratory study suggests that the ACTIVITY self-report instrument is a moderately valid instrument for measuring general activity levels of young children during the school year, including during specified periods of time. The potential for video technology to facilitate accurate physical activity recall in young children warrants further study.

Activities of Daily Living↗
PubMed2001

Multilevel modelling of hierarchical data in developmental studies.

This report attempts to give nontechnical readers some insight into how a multilevel modelling framework can be used in longitudinal studies to assess contextual influences on child development when study samples arise from naturally formed groupings. We hope to achieve this objective by: (1) discussing the types of variables and research designs used for collecting developmental data; (2) presenting the methods and data requirements associated with two statistical approaches to developmental data--growth curve modelling and discrete-time survival analysis; (3) describing the multilevel extensions of these approaches, which can be used when the study of development includes intact clusters or naturally formed groupings; (4) demonstrating the flexibility of these two approaches for addressing a variety of research questions; and (5) placing the multilevel framework developed in this report in the context of some important issues, alternative approaches, and recent developments. We hope that readers new to these methods are able to visualize the possibility of using them to advance their work.

Adolescent↗
PubMed2000

Secular trends in the body mass index of Canadian children.

BACKGROUND: Various changes in society have created the opportunity for more sedentary behaviour and the consumption of food that is high in kilojoules, which may lead to a progressive increase in body mass over time. The purpose of this study was to examine secular changes in the body mass index (BMI) of Canadian children between 1981 and 1996. METHODS: Nationally representative data from the 1981 Canada Fitness Survey, the 1988 Campbell's Survey on the Well-being of Canadians and the 1996 National Longitudinal Survey of Children and Youth were used in the analysis. Regression analyses were used to assess population changes in BMI from 1981 to 1996 for children aged 7-13 years. Changes in the distribution of BMI results were evaluated by plotting the residuals from regression analyses of BMI on age, assessed separately by sex, using the 1981 data as baseline. The proportions of children exceeding the 85th and 95th age- and sex-specific percentiles from the 1981 (baseline) data were also calculated. RESULTS: Since 1981, BMI has increased at the rate of nearly 0.1 kg/m2 per year for both sexes at most ages, indicating a clear secular trend toward an increase in BMI of Canadian children. The prevalence of overweight among boys increased from 15% in 1981 to 28.8% in 1996 and among girls from 15% to 23.6%. The prevalence of obesity in children more than doubled over that period, from 5% to 13.5% for boys and 11.8% for girls. INTERPRETATION: Secular trends indicate that Canadian children aged 7-13 years are becoming progressively overweight and obese.

Adolescent↗
PubMed1999

Place effects for areas defined by administrative boundaries.

This study estimates the effects of place on the distribution of health problems, health-related quality of life, general well-being, and family functioning for youths and adults aged 12 years and older. Data come from the Ontario Health Survey, a cross-sectional study done in 1990 to provide baseline statistical data on population health within 42 public health units throughout the province. Place effects were generally small and were influenced by both the size of the geographic area used to define place and the health indicator selected for study. Variations in health explainable at the public health region level were less than 1%. Variations in health explainable within smaller geographic boundaries (enumeration areas) ranged from 4.7% for health problems to 0.2% for family functioning. Adjustment for area differences in the age, gender, education, marital status, income, and birthplace of inhabitants reduced these place effects at the enumeration area level to 3.7% for health problems and to less than 0.1% for family functioning. The lack of evidence for place effects within large jurisdictional boundaries raises questions about both the usefulness of carrying out health needs assessment surveys within these areas and the informativeness of these geographic boundaries for studying place effects.

Adolescent↗