Adults in South Africa with high blood pressure and hypertension who received short message system (SMS) text messages on their mobile phones had improved adherence to their medications and small reductions in systolic blood pressure compared with a group that did not receive reminders.

The intervention’s effectiveness did not differ between men and women, younger and older patients and patients with and without comorbid conditions.

Lead researcher Kirsten Dobrow, DPhil, of the University of Oxford in the U.K., and colleagues published their results online in Circulation on Jan. 14.

“This is the first study to report a small impact on objectively measured blood pressure using support via text-messaging without additional blood pressure monitoring, and without health care providers contacting non-adherent patients,” they wrote. “We found no evidence that an interactive intervention delivered with the same frequency as an information-only intervention had a greater effect on adherence or blood pressure, in contrast to findings from other mobile phone-based interventions. This might be explained by the older average age of participants in this trial compared with other mobile phone based studies and could indicate either an age-based or experience based difference in how people make use of such technology.”

The researchers randomized 1,372 adults at a primary care facility in Cape Town, South Africa, between June 26, 2012, and Nov. 23, 2012, to receive information-only SMS text messages, interactive SMS text messages or their usual care.

The primary care facility serves a community in which 51 percent of people are black Africans and 48 percent are of mixed ancestry. In addition, approximately one-third of households live in informal dwellings or shacks and 64 percent have a monthly income of less than $270. In the community, primary healthcare services and medicines are provided for free, while doctors or prescribing nurses meet with patients with chronic diseases every three to six months. Patients with high blood pressure or those receiving treatment for the first time meet with doctors and nurses more frequently.

The participants were at least 21 years old and were diagnosed with hypertension, prescribed blood pressure lowering medications and had a systolic blood pressure of less than 220 mm Hg and diastolic blood pressure of less than 120 mm Hg.

The mean age was 54.3 years old, while 28 percent of participants had hypertension for at least 10 years. In addition, 50.2 percent of participants in the interactive SMS group responded to a message during the trial.

All participants received care from the clinic as well as written information about hypertension and healthy living. Participants in the SMS text messaging groups received text messages each week, which were designed to increase adherence and persistence with treatment. Participants in the interactive text messaging group were able to use a free service that allowed them to cancel or change an appointment and change the timing and language of their messages.

After 12 months, the mean adjusted change in systolic blood pressure was reduced 2.2 mm Hg in the information-only SMS text message group and reduced 1.6 mm Hg in the interactive SMS text message group compared with the usual care group.

The proportion of participants who adhered to their medications at least 80 percent of the time during the 12 months was 62.8 percent in the information-only SMS text message group, 59.7 percent in the interactive SMS text message group and 49.4 percent in the usual care group.

In addition, there were no differences in health status, attendance at clinic appointments, retention in clinical care, treatment and clinic satisfaction, hypertension knowledge, self-reported adherence, hospital admissions and differences in medication changes.

During the 12-month follow-up period, 17 patients died: three in the usual care group and seven apiece in the text messaging groups.

The researchers cited a few limitations of the study, including that participants received medications for free and were recommended to have follow up visits, which may have increased adherence. The researchers also could not evaluate the observed difference in systolic blood pressure between the groups. Further, they measured adherence only included dispensing in the clinic and not taking the medication.