Stage-matched nutrition guidance for patients at elevated risk for cardiovascular disease: A randomized intervention study in family practice

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Original Research

Stage-matched nutrition guidance for patients at elevated risk for cardiovascular disease: A randomized intervention study in family practice

J Fam Pract. 2002 September;51(9):751-758

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References

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FIGURE 2
Intervention scheme with clarification

Data analyses

Differences between groups at baseline and follow-up were tested with unpaired t-tests for continuous variables and with chi-square tests for categorized variables. If the number of observations within 1 cell was less then 5, a Fisher’s exact test was used instead of a chi-square test. Differences within subjects were tested with a paired t-test. P values less than 0.05 were considered significant. Because of clustering of patients within practices, a multilevel analysis was also carried out (level 1 patient, level 2 practice). All analyses were performed on the basis of intention to treat. SAS version 6.12 was used for the statistical analyses (SAS Institute Inc., Cary, NC, USA).

Results

Study population

The study sample was predominantly female (73%), poorly educated (68%), with an average age of 58 years (see Table 1) for definitions of educational level). Of the cardiovascular risk factors, hypertension was present in 92% of participants, type 2 diabetes mellitus in 6%, both disorders in 2%, and a family history of heart disease in 25%. No significant differences were found between the intervention group (n=71) and the control group (n=72) (Table 1). Table 2 demonstrates that the 2 study groups also showed comparable baseline measures according to dietary intake, anthropometry, and serum lipid levels. The mean BMI of the total group of subjects was 28.7 kg/m 2 ; 83% had a BMI higher than 25 and the majority had high total cholesterol and dietary fat intake.

Intervention-related measures

At baseline, 51% of the patients in the intervention group were classified in the precontemplation stage, 24% in the contemplation stage, and 25% in the action stage. They had consulted their FP once (n=53) or twice (n=18) before they were referred to the study dietician (n=60). Eleven patients were not referred to the dietician because they did not reach the action stage. All of the referred patients but one received 3 consultations with the dietician. In the control group, 24% of the patients discussed nutrition issues with their FP, 57% read nutrition brochures related to cardiovascular topics, and 1% (7) were referred to a dietician.

Changes at follow-up measurements

After 6 months (Table 2) total energy intake was reduced by 1.4 and 0.6 MJ in the intervention and control groups, respectively; total fat intake by 7.9% and 2.2 % of total energy, and saturated fat intake by 3.4% and 0.8% of total energy. The reductions were significantly larger in the intervention group, except for unsaturated fat. This was also reflected in risk factors: body weight and BMI declined significantly more in the intervention group (1.5 kg body weight) than in the control group (0.6 kg body weight). We found no significant differences between groups for waist circumference and waist-hip ratio.

The reduced fat intake in the intervention group was maintained at 12 months, although the differences were smaller. Changes in energy intake and anthropometric values at this time no longer differed significantly with multilevel analysis. During the 12 months of the study, slight reductions were found for serum total cholesterol (intervention group: 2.3 mg/dL, controls: 6.2 mg/dL), LDL cholesterol (intervention group: 6.2 mg/dL, controls: 7.7 mg/dL), and triglycerides (intervention group: 0.8 mg/dL, controls: 3.1 mg/dL). HDL cholesterol increased slightly in both groups (3.9 mg/dL in the intervention group, 2.7 mg/dL in the control group). However, none of these differences were significant. There were no significant changes in smoking or physical activity (P values of chi-square tests per measurement moment were >0.85), and none of the patients was prescribed a cholesterol-lowering drug. The significance of the P values of the differences in variables between the first and last measurement moment did not change when multilevel analysis was performed, except for body weight (Table 2).

TABLE 2
Baseline measures and changes after 6 months and 12 months in dietary intake and anthropometry

	At Baseline			At 6 months			At 12 months
	Intervention	Control	P*	Intervention	Control	P**	Intervention	Control	P**	P***
	n=71 Mean ± SD	n=72 Mean ± SD		n=70 Mean ± SD	n=67 Mean ± SD		n=67 Mean ± SD	n=63 Mean ± SD
Dietary intake (per day)
Total energy (MJ/d)¹	9.1 ± 2.7	9.6 ± 2.6	0.25	-1.4 ± 1.9†	-0.6 ± 1.8†	0.01	-0.7 ± 3.0	-0.9 ± 2.4†	0.09	0.00
Total fat (% of energy)	42.1 ± 6.3	42.6 ± 5.2	0.64	-7.9 ± 6.5†	-2.2 ± 4.9†	0.00	-5.6 ± 6.9†	-2.0 ± 6.7†	0.00	0.00
Saturated fat (% of energy)	15.2 ± 2.6	15.5 ± 2.3	0.42	-3.4 ± 2.7†	-0.8 ± 2.2†	0.00	-2.6 ± 2.7†	-0.9 ± 2.6†	0.00	0.00
Monounsaturated fat (% of energy)	14.6 ± 3.3	14.9 ± 2.6	0.53	-3.4 ± 3.3†	-0.7 ± 2.4†	0.00	-1.9 ± 4.1†	-0.3 ± 3.3	0.01	0.00
Unsaturated fat (% of energy)	9.4 ± 3.0	9.3 ± 3.0	0.79	-1.0 ± 3.1†	0.8 ± 3.0†	0.37	-1.0 ± 2.7†	-0.7 ± 3.7	0.73	0.73
Cholesterol (mg)	239.1 ± 91.5	254.8 ± 90.8	0.31	-62.0 ± 68.9†	-22.8 ± 66.4†	0.00	-46.4 ± 77.1†	-33.4 ± 83.1†	0.02	0.03
Anthropometry
Body weight (kg)	79.2 ± 14.9	80.3 ± 12.0	0.63	-1.3 ± 1.8†	-0.6 ± 1.9†	0.01	0.2 ± 3.0	-0.6 ± 2.8†	0.02	0.06
Body Mass Index (kg/m²)	28.1 ± 4.3	29.2 ± 4.8	0.15	-0.5 ± 0.6†	-0.2 ± 0.7†	0.01	0.0 ± 1.1	-0.2 ± 1.0†	0.03	0.08
Waist circumference (cm)	94.3 ± 12.1	97.7 ± 10.3	0.08	-1.6 ± 4.9†	-1.7 ± 5.2†	0.43	-1.6 ± 6.6†	-1.8 ± 5.6†	0.61	0.86
Waist-hip circumference ratio	0.89 ± 0.07	0.90 ± 0.09	0.36	-0.0 ± 0.04	-0.01 ± 0.05†	0.13	0.01 ± 0.05†	-0.02 ± 0.05†	0.15	0.15
1 Joule=0.24 cal
*Two-sided P values for differences in baseline measures between intervention and control group.
**One-sided P value for difference in change from baseline between intervention and control group.
***P value with multilevel analysis
†Significant difference in changes after 6 and 12 months compared to baseline within group (one-sided P value<0.05).