Text Message Intervention for Prevention of Cardiovascular Disease in Primary Care Patients With Hypertension

Background- The globalization of unhealthy lifestyles and demographic ageing of the world's population has contributed to the fact that high blood pressure is classified by World Health Organization as the world's leading risk for mortality.

Persistent hypertension is a key risk factor for coronary heart disease (CHD), stroke and other cardiovascular diseases (CVD), such as heart failure. CVD is, despite a decline in recent decades, still the leading cause of death in Sweden (4). The prevalence of hypertension in adults is around 40% according to a recent multinational study (5). In 30-40% of hypertensive individuals, additional metabolic risk factors such as dyslipidemia, insulin resistance and elevated glucose occur simultaneously, which further multiply the risk for heart disease, diabetes and stroke. An unhealthy lifestyle with physical inactivity and excess energy intake is the major driver of these metabolic risk factors. In most cases lifestyle intervention can reverse or reduce the unfavorable metabolic profile.

Primary healthcare in Sweden is managing the first-line healthcare, offering both prevention and treatment for a majority of chronic diseases. In Sweden, the vast majority of patients with hypertension are treated in primary health care. If the hypertension is well controlled, the GP typically meets the patient once a year for medical checkup, blood tests and medical prescription.

Interventions by SMS-texting have been shown to significantly improve compliance to medications, follow-up rate or disease monitoring.

Trial Design - Randomised clinical trial

Intervention - The experimental treatment will consist of an SMS-intervention addressing metabolic risk factors associated with cardiovascular disorders in patients with hypertension.

After baseline measurement participants in the intervention group will receive four semi-personalized messages per week in addition to their usual care according to the National Board of Health and Welfare guidelines for hypertension treatment. The text messages will be developed to support healthy life style changes i.e. regarding general cardiovascular health, tobacco use, physical activity and diet.

Control Treatment - The control group will receive usual care according to the National Board of Health and Welfare guidelines for hypertension treatment.

Recruitment - The participants will be recruited consecutively from three different PHCCs in Skåne. Patients with hypertension will receive information about the study at their annual check-up or other appointment with their GP. If they choose to participate, they will be contacted by phone by a research assistant for additional information, possibility to ask questions about the study, and scheduling a baseline control at their PHCC.

Baseline examination - Included patients that consent to take part in the study will be invited to their PHCC for a baseline visit. The following measurements will be assessed by a research assistant: blood pressure (in sitting position after 5 minutes rest; mean of two measurements in a standardized procedure with validated electronic BP devices), BMI and waist-hip circumference. Furthermore, the patients will complete a short questionnaire for evaluation of medical history, medication, tobacco and alcohol use, physical activity level, self-rated health and health-related quality of life. Blood samples for fasting plasma glucose, HbA1c and cholesterol will be drawn in the morning within a few days after the baseline visit.

Randomization- Randomization to study groups will be performed after completion of baseline assessments and questionnaires. A computer generated random number schedule with block sizes of four will be prepared. To assure allocation concealment, the information about group affiliation will be delivered through sealed envelopes.

The research assistant, the patients' GPs, as well as all researchers except Magnus Sandberg (MS) will be blinded to group allocation. If the patients have questions regarding the SMS function they will be able to contact MS for help.

Follow up- Follow up control will be performed after 6 months with the same assessments as at the baseline visit.

Power and sample size - For the pilot study we have assumed that a total number of 60 patients (20 patients per PHCC) will be sufficient to evaluate the feasibility of the intervention and the logistics of the assessments.

For the future full scale study, each group must contain 143 participants. The sample size is based on an assumed statistical power of 80 %, a two-sided test, a significance level of 5 %, a difference of 5 mm Hg between the groups, a standard deviation of 14 mm Hg and a drop out rate of 15 %.

Analysis plan - Data will be analysed according to the Intention-to-treat principle. Differences in mean change of end points between intervention and control groups will be calculated by ANCOVA, with baseline values as covariates.