| Variables being investigated | Study | Measurement of adherence | Study setting and sample size |
| Cost of medications | Bhandari et al. [33] | MMAS 4 | Nepal; N = 154 |
| Nsitou [41] . | Questionnaire | Congo; N = 212 | |
| Eizubier [52] | Pill count | Sudan ; N = 198 | |
| Praveen [30] | Questionnaire | India; N = 804 | |
| Number of pills | Bhandari et al. [33] | MMAS 4 | Nepal; N = 154 |
| Srikanth et al. [53] | MMAS 8 | India; N = 304 | |
| Olowookere [47] | Questionnaire | Nigeria; N = 420 | |
| Ramli [54] | The hill bone adherence to BP scale and MMAS 8 | Malaysia; N = 653 | |
| Bilal et al. [44] | Questionnaire | Pakistan; N = 113 | |
| Srivastava et al. [55] | Self-report and MMAS 4 | India; N = 440 | |
| Forgetfulness | Campbell et al. [42] | Morisky Green | Nigeria; N = 262 |
| Al-Ramahi [38] | MMAS 8 | Palestine; N = 450 | |
| Side effect of medicine | Lalic et al. [28] | MMAS 8 | Serbia ; N = 170 |
| Shima [51] | Qualitative | Malaysia | |
| Odusola [40] | Qualitative | Nigeria | |
| Duration of therapy | Bhandari et al. [33] | MMAS 4 | Nepal; N = 154 |
| Hareri et al. [45] | Questionnaire | Ethiopia; N = 286 | |
| Lalic et al. [28] | MMAS 8 | Serbia; N = 170 | |
| Bilal et al. [44] | Questionnaire | Pakistan; N = 113 | |
| Hu et al. [56] | Questionnaire | China; N = 318 | |
| Distance from health care facilities | Gelaw et al. [35] | Questionnaire | Ethiopia; N = 91 |
| Al Ramahi [38] | MMAS 8 | Palestine; N = 450 | |
| Ambaw et al. [37] . | MMAS 4 | Ethiopia; N = 384 |