The design of this parallel group randomised trial has been described elsewhere.14
Twenty general practices were allocated to intervention and control conditions (see website) using the minimisation technique15
to balance groups for the Jarman score of social deprivation,16
ratio of patient to practice nurse hours per week, and fundholding status (including wave of entry).
Patients were recruited on the basis of one or more modifiable cardiovascular risk factors: regular cigarette smoking (more than one cigarette per day), high serum cholesterol cocentration (6.5-9.0 mmol/l), or combined high body mass index (25-35) and low physical activity (fewer than 12 episodes of vigorous or moderate exercise for at least 20 minutes in the past 4 weeks, according to criteria based on the national fitness survey).17
Patients were excluded if they were on active follow up or drugs for coronary heart disease, had had cardiovascular disease or peripheral vascular disease, had a serious chronic illness, or were prescribed a special diet or lipid lowering drugs.
The target sample size was 100 patients per practice. Taking intracluster correlations of risk factors into account, we calculated that this would detect a drop in smoking prevalence from 50% to 41%, and a decrease of 0.27 mmol/l in total serum cholesterol concentration with 90% power at the 5% significance level.
After recruitment and baseline assessment patients were counselled by practice nurses in smoking cessation, dietary fat reduction, and increasing physical exercise as appropriate either using behaviourally oriented methods (intervention group) or their own usual methods, involving information provision and exhortation. Patients were reassessed at 4 and 12 months.
One practice nurse from each of the 10 intervention practices was trained in behavioural counselling on the basis of the stage of change model. Training was adapted from the Health Education Authority’s package Helping People Change
Nurses were trained both to assess a patient’s readiness to change behaviour and to use attitude change, goal setting, and specific behavioural advice to enable change. Training took place over 3 days, with a retraining and refresher day after 6 months. The goal in the smoking intervention was complete abstinence, and counselling was supported by nicotine replacement therapy when appropriate.20
Patients with increased serum cholesterol concentration were counselled to reduce dietary fat intake and to increase fruit and vegetable consumption within the context of a balanced diet, without specifying targets of the proportion of energy derived from fats. Patients with combined increased body mass index and lack of regular physical activity were counselled to increase their activity levels to 12 sessions of moderate or vigorous activity per month.
Patients in the intervention arm of the study were invited for three counselling sessions if they had two risk factors and for two counselling sessions if they had only one risk factor. The order in which risk factors were targeted was determined after negotiation between nurse and patient. Counselling sessions were scheduled to last no more than 20 minutes, and between sessions the nurse contacted the patient by telephone one or two times to consolidate the counselling and to encourage behaviour change.
The physical assessment measures were calculation of body weight and body mass index, and total serum cholesterol concentration and blood pressure. Cholesterol was measured in all patients at 12 months, but at 4 months only in those with initially increased concentrations. Smoking status was assessed with validated questions,21
and patients who stopped smoking during the study and were not currently using nicotine replacement therapy were asked to provide a saliva sample for measurement of cotinine. The smoking outcome measures were abstinence as verified by measurement of cotinine at 4 and 12 months together with reported number of cigarettes smoked per day. Dietary fat intake was assessed with the dietary instrument for nutritional education.22
Physical activity was measured as the number of episodes of vigorous or moderate activity (as defined in the national fitness survey assessment instrument) completed in the past 4 weeks. Stage of change for smoking cessation, dietary fat reduction, and increasing physical activity were assessed with measures described elsewhere.23
Statistical comparison of intervention and control groups was carried out with weighted means for each practice thereby taking account of cluster effects.24