Highlights of this issue

CMAJ 2000;163(11):1421

Children in the Western world are becoming heavier, and Canadian children are no exception. Mark Tremblay and Douglas Willms used data from 3 national databases to compare the body mass index (BMI) of children aged 7–13 in 1981, 1988 and 1996. Since 1981 the BMI has increased by nearly 0.1 kg/m² per year for both sexes. In 1981, 15% of children were overweight and 5% obese. In 1996, 28.8% of boys and 23.6% of girls were overweight and 13.5% of boys and 11.8% of girls were obese. In a related commentary Ross Andersen discusses causes, including the sacrifice of school physical education programs to budgetary restraint.

Sedentary habits are not limited to children. Only 34% of Canadians aged 22–55 years meet the recommendations in Canada's Physical Activity Guide to Healthy Active Living. Peter Katzmarzyk and colleagues calculated the economic burden of physical inactivity, based on the summary relative risk estimates for coronary artery disease, stroke, colon cancer, breast cancer, type 2 diabetes mellitus and osteoporosis. About $2.1 billion, or 2.5% of Canada's direct health care costs, were attributable to physical inactivity in 1999. A 10% reduction in the prevalence of inactivity could potentially reduce direct health care costs by $150 million annually. Robert Kaman in turn considers strategies for promoting physical fitness; simple awareness of the personal and economic costs is not enough to motivate individual change.

Since the Canadian Task Force on Preventive Health Care last reported on the prevention of child maltreatment, in 1993, there have been efforts to evaluate strategies intended to reduce physical abuse, sexual abuse, neglect and emotional abuse in childhood. These strategies have included screening techniques such as identification of risk indicators, preventive programs such as home visitation by nurses, comprehensive health care programs, parent education and support programs, and combined services and programs aimed specifically at preventing sexual abuse. In this update the task force reports on the evidence for and against these interventions.

• Hematologic dyscrasia associated with ticlopidine therapy: evidence for causality [Research]
• Bayesian assessment of adverse drug reactions [Commentary]

Several rare, potentially fatal types of hematologic dyscrasia, such as agranulocytosis, aplastic anemia, neutropenia, pancytopenia, thrombocytopenia and thrombotic thrombocytic purpura (TTP), have been associated with ticlopidine therapy. Fran Paradiso-Hardy and colleagues evaluated 91 published case reports using the Bayesian Adverse Reaction Diagnostic Instrument to calculate the posterior probability that ticlopidine was the cause. The median posterior probability values (and range) for agranulocytosis, aplastic anemia, neutropenia, pancytopenia, thrombocytopenia and TTP were 0.95 (0.53–0.98), 0.81 (0.57–0.93), 0.86 (0.75–0.96), 0.78 (0.61–0.89), 0.74 (0–0.92) and 1.0 (0.33–1.00) respectively. The posterior probability was 0.75 or greater in 82 (90%) of the case reports. In a related commentary Tom Hutchinson elaborates on the interpretation of these figures and the value of using statistical analysis instead of subjective judgements in establishing causality.

Endocrine-disrupting chemicals are ubiquitous in the environment. Longer-lasting representatives, such as DDT, PCBs and dioxins, are detectable in nearly all human blood samples. Gina Solomon and Ted Schettler describe the potential health implications of exposure to endocrine-disrupting chemicals. Exposed animals show effects including altered sexual behaviour, birth defects and compromised fertility. Human surveillance-based studies have shown increases in some potentially hormone-related conditions. The fetus is particularly sensitive to hormonal fluctuations. Cohort studies involving children exposed in utero to PCBs have shown delayed psychomotor development and increased distractibility among those most exposed. Many endocrine-disrupting chemicals are targeted for elimination, but some are still in commercial use. Political decision-making is hampered by scientific uncertainty. The medical community can play a critical role in evaluating the data, educating the public and protecting future generations.

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