Christopher Silagy

The effectiveness of exercise training in lowering blood pressure: a meta-analysis of randomised controlled trials of 4 weeks or longer

Objective: To identify the features of an optimal exercise programme in terms of type of exercise, intensity and frequency that would maximise the training induced decrease in blood pressure (BP).Data identification: Trials were identified by a systematic search of Medline, Embase and Science Citation Index (SCI), previous review articles and the references of relevant trials, from 1980 until 1996, including only English language studies.Study selection: The inclusion criteria were limited to randomised controlled trials of aerobic or resistance exercise training conducted over a minimum of 4 weeks where systolic and diastolic BP was measured.Results: A total of 29 studies (1533 hypertensive and normotensive participants) were included, 26 used aerobic exercise training, two trials used resistance training and one study had both resistance and aerobic training groups. Aerobic exercise training reduced systolic BP by 4.7 mm Hg (95% CI: 4.4, 5.0) and diastolic BP by 3.1 mm Hg (95% CI: 3.0, 3.3) as compared to a non-exercising control group, however, significant heterogeneity was observed between trials in the analysis. The BP reduction seen with aerobic exercise training was independent of the intensity of exercise and the number of exercise sessions per week. The evidence for the effect of resistance exercise training was inconclusive.Conclusions: Aerobic exercise training had a small but clinically significant effect in reducing systolic and diastolic BP. Increasing exercise intensity above 70% VO2 max or increasing exercise frequency to more than three sessions per week did not have any additional impact on reducing BP.

Exercise training and blood lipids in hyperlipidemic and normolipidemic adults: A meta-analysis of randomized, controlled trials

Objective: To determine the effectiveness of exercise training (aerobic and resistance) in modifying blood lipids, and to determine the most effective training programme with regard to duration, intensity and frequency for optimizing the blood lipid profile.Design: Trials were identified by a systematic search of Medline, Embase, Science Citation Index (SCI), published reviews and the references of relevant trials. The inclusion criteria were limited to randomized, controlled trials of aerobic and resistance exercise training which were conducted over a minimum of four weeks and involved measurement of one or more of the following: total cholesterol (TC), high density lipoprotein (HDL-C), low density lipoprotein (LDL-C) and triglycerides (TG).Subjects: A total of 31 trials (1833 hyperlipidemic and normolipidemic participants) were included.Results: Aerobic exercise training resulted in small but statistically significant decreases of 0.10 mmol/L (95% CI: 0.02, 0.18), 0.10 (95% CI: 0.02, 0.19), 0.08 mmol/L (95% CI: 0.02, 0.14), for TC, LDL-C, and TG, respectively, with an increase in HDL-C of 0.05 mmol/L (95% CI: 0.02, 0.08). Comparisons between the intensities of the aerobic exercise programmes produced inconsistent results; but more frequent exercise did not appear to result in greater improvements to the lipid profile than exercise three times per week. The evidence for the effect of resistance exercise training was inconclusive.Conclusions: Caution is required when drawing firm conclusions from this study given the significant heterogeneity with comparisons. However, the results appear to indicate that aerobic exercise training produced small but favourable modifications to blood lipids in previously sedentary adults.Sponsorship: Public Health Research and Development Project Grant, National Health and Medical Research Council, Department of Health, Housing, Local Government and Community Services, 1995.

Garlic: its cardio-protective properties.

Evidence that garlic inhibits platelet aggregation, increases fibrinolysis, reduces blood pressure, enhances anti-oxidant activity, and reduces serum lipids suggests that it may have cardio-protective properties. The lack of qualitative standardization of garlic preparations and the methodological weaknesses of earlier studies makes comparison between different studies complicated. Quantitative pooling of data in meta-analyses of the primary trials strongly suggests that garlic is an effective lipid-lowering agent.

Community-based recruitment strategies for a longitudinal interventional study: the VECAT experience

This article examines different recruitment strategies for the VECAT Study, a 4-year, double-masked, placebo-controlled, randomized clinical trial of vitamin E in the prevention of cataract and age-related maculopathy. Five recruitment methods were employed: newspaper advertising, radio advertising, approaches to community groups, approaches via general practices, and an electoral roll mail-out. Participants (1204) from the community in Melbourne, Australia were recruited and enrolled within 15 months (age range: 55-80 years, mean 66 years; gender ratio: 57% female, 43% male). The electoral roll mail-out and newspaper advertising were the most efficient methods of recruitment in terms of absolute numbers of participants recruited and cost per participant. Recruitment for the VECAT study was successfully completed within the planned period. Although the electoral roll mail-out and newspaper advertising were the most efficient for this study, other methods may be of value for studies with different subject selection criteria.

Use of systematic reviews in clinical practice guidelines: case study of smoking cessation

Abstract Objective: To examine the extent to which recommendations in the national guidelines for the cessation of smoking are based on evidence from systematic reviews of controlled trials. Design: Retrospective analysis of recommendations for the national guidelines for the cessation of smoking. Materials: National guidelines in clinical practice on smoking cessation published in English. Main outcome measures: The type of evidence (systematic review of controlled trials, individual trials, other studies, expert opinion) used to support each recommendation. We also assessed whether a Cochrane systematic review was available and could have been used in formulating the recommendation. Results: Four national smoking cessation guidelines (from Canada, New Zealand, the United Kingdom, and the United States) covering 105 recommendations were identified. An explicit evidence base for 100%, 89%, 68%, and 98% of recommendations, respectively, was detected, of which 60%, 56%, 59%, and 47% were based on systematic reviews of controlled studies. Cochrane systematic reviews could have been used to develop between 39% and 73% of recommendations but were actually used in 0% to 36% of recommendations. The UK guidelines had the highest proportion of recommendations based on Cochrane systematic reviews. Conclusions: Use of systematic reviews in guidelines is a measure of the “payback” on investment in research synthesis. Systematic reviews commonly underpinned recommendations in guidelines on smoking cessation. The extent to which they were used varied by country and there was evidence of duplication of effort in some areas. Greater international collaboration in developing and maintaining an evidence base of systematic reviews can improve the efficiency of use of research resources.

Recruitment of Older Adults for a Randomized, Controlled Trial of Exercise Advice in a General Practice Setting

OBJECTIVES: The success of any clinical trial depends strongly on recruiting enough participants in a reasonable time period. This paper aims to identify the obstacles, as well as the successful aspects, of recruiting of older participants into an exercise study.

Aspirin and neoplasia of the digestive tract: is there a chemopreventive effect?

There has been much recent interest in the hypothesis that aspirin and other non-steroidal anti-inflammatory agents (NSAIDs) protect against gastrointestinal, particularly colorectal, carcinoma. Three lines of evidence support this hypothesis: First, NSAIDs inhibit the growth of colorecal neoplasms in laboratory rodents. Epidemiological studies in humans also suggest a protective effect. Three case control and two cohort studies have examined the relation between aspirin use and large bowel neoplasia, and four of these five studies found a risk reduction for either incidence or mortality of about 50% in regular users of aspirin. Finally, two small intervention studies in patients with familial polyposis showed a short-term reduction in polyp formation in patients treated with NSAIDs. In contrast, a large randomized trial of aspirin in human subjects detected no reduction in incidence of colorectal carcinoma in those assigned to aspirin compared to placebo. Colorectal cancer is common and an effective primary prevention strategy could lead to significant public health benefits. Further research into the potential of aspirin to achieve this is keenly awaited. It is, however, premature to recommend it specifically for this purpose on the basis of current evidence, given the known adverse effects of aspirin and related compounds, especially on the gastrointestinal tract.

Health economic reviews. Are they compiled systematically

Attempts to perform economic reviews of randomized controlled trials frequently lack a systematic approach. This conclusion is consistent with the findings of previous analyses of review articles in other fields, which have highlighted the failure to apply the same degree of rigor to this type of research synthesis that the scientific community has come to expect from primary research articles.

Can Resource Use be Extracted from Randomized Controlled Trials to Calculate Costs?: A Review of Smoking Cessation Interventions in General Practice

The ability to extract information on resource use from randomized controlled trials can provide the groundwork for systematically compiling health economic reviews of health interventions. A review of the brief smoking interventions in general practice demonstrates that not all the necessary information can be extrapolated from these trials, and cost data will have to be supplemented from other sources.

Modelling different strategies to prevent coronary heart disease in primary care

Strategies for prevention of coronary heart disease (CHD) in primary care need to take into account the number of people who require screening, further assessment, intervention and follow-up (i.e. the patient workload generated for the general practitioner) as well as the anticipated reductions in morbidity and mortality. Risks of CHD for various risk profiles were estimated from equations produced by the Framingham study. This enabled an estimate of the number of avertable CHD events to be compared against the patient workload implications for the general practitioner when different screening and intervention strategies were used. The Framingham equations were applied to a population of 5727 men and women aged 35-64 years of age registered with general practices in the south of England. Adopting an unselective approach to screening resulted in 14.1% (n = 73) of the 517 CHD events predicted over a 10 year period being averted. A limited screening strategy, involving 25% (n = 1436) of the patients would avert 5.6% (n = 29) of the predicted CHD events, whilst more extended strategies involving between 37% (n = 2131) and 46% (n = 2660) of the practice population respectively would result in between 6.9% (n = 36) and 9.3% (n = 48) of events being averted. The marginal benefit in averting CHD events decreased as more screening criteria were included. Almost all (99%) of the people identified by the selective screening strategies would require some form of intervention, predominantly lifestyle advice. Lowering the systolic blood pressure by 15 mmHg instead of 10 mmHg was equally effective as a 5% improvement in the overall rate of smoking cessation.(ABSTRACT TRUNCATED AT 250 WORDS)