Medication adherence interventions for South Asian populations with cardiovascular disease: A systematic review and narrative synthesis.

South Asian populations experience a disproportionate burden of cardiovascular disease (CVD) globally, with evidence consistently highlighting suboptimal medication adherence across both regional and diaspora settings. While previous research has primarily identified socio-cultural barriers to adherence, there is a critical need to analyse the effectiveness and feasibility of interventional solutions to improve medication adherence in this population. This systematic review synthesised evidence on the reported effectiveness and feasibility of such interventions from 29 studies published between 2004 and 2025. Data from India, Pakistan, Nepal, Sri Lanka, Bangladesh and diaspora settings (e.g., United Kingdom), were analysed using a narrative synthesis approach. Twenty-six studies reported statistically significant improvements in adherence (p < 0.05). The interventions identified spanned seven themes: behavioural/educational strategies, task-shifting models, mHealth tools, regimen simplification, socio-cultural determinants, measurement of adherence and cultural inclusion practices. The findings highlight a clear 'sustainability gap', where short-term technological or educational bursts often fail to maintain long-term adherence without sustained human interaction or professional follow-up. Furthermore, while pharmacological simplification via polypills, mHealth reinforcement and task-shifting models are effective and feasible, there remains a critical paucity of culturally tailored, faith-sensitive interventions designed to address non-adherence driven by socio-cultural beliefs. Future research must transition toward robust, context-specific socio-cultural adaptation by incorporating objective adherence measures and individualised care models that engage faith-based factors. Ultimately, achieving equitable cardiovascular outcomes in this population requires a multi-level approach that integrates professional reinforcement with scalable technology to ensure long-term sustainability beyond short-term trial effects.