Non-adherence to anti-hypertensive medication in low- and middle-income countries: a systematic review and meta-analysis of 92443 subjects

Hypertension is a rising global burden, and low-and middle-income countries account for 80% of deaths due to complications of hypertension. Hypertension can be controlled by adhering to anti-hypertensive medication. However, non-adherence is an increasing challenge. This review aims to systematically evaluate non-adherence to anti-hypertensive medication among adults in low-and middle-income countries and explore factors affecting non-adherence to anti-hypertensive medication. We performed a systematic search for studies published between 1 January 2000 and 31 August 2015. A selection process was performed for data extraction with a combination of Medical Subject Headings terms: 'hypertension' and 'adherence'. Further search criteria were: language ('english'), species ('humans'), and low-and middle-income countries. A total of 22 studies met the inclusion criteria. The pooled percentage of non-adherence when using the eight-item Morisky Medication Adherence Scale (MMAS) was 63.35% (confidence of interval (CI): 38.78-87.91) and 25.45% (CI: 17.23-33.76) when using the 80 and 90% cut-off scales. The factors were classified into the five dimensions of adherence defined by the World Health Organization, and the majority of the studies reported factors from the dimension 'social and economic factors'. This systematic review demonstrated considerable variation of non-adherence to anti-hypertensive medication in low-and middle-income countries depending on the methods used to estimate non-adherence. The results showed a high non-adherence when the MMAS eight-item scale was used and low when the 80 and 90% cut-off scales were used. The majority of factors affecting non-adherence to anti-hypertensive medication fell within the World Health Organization defined dimension 'social and economic factors'.