There is strong evidence that many patients with chronic illnesses including asthma, hypertension, diabetes and HIV/AIDS, have difficulty adhering to their recommended regimens. This results in less than optimal management and control of the illness. Poor adherence is the primary reason for suboptimal clinical benefit (1,2). It causes medical and psychosocial complications of disease, reduces patients' quality of life, and wastes health care resources. Taken together, these direct consequences impair the ability of health care systems around the world to achieve population health goals.

The conclusions of research in this area are unequivocal - adherence problems are observed in all situations where the self-administration of treatment is required, regardless of type of disease, disease severity and accessibility to health resources. While it may seem to be a simple issue, many factors contribute to adherence problems. Although some of these factors are patient-related, the characteristics of the disease and its treatment, and attributes of the health care system and service delivery also have great influence. Adherence problems have generally been overlooked by health stakeholders, and as a result have received little direct, systematic, intervention. Three prevalent chronic diseases, diabetes, hypertension and asthma provide compelling illustrations of different facets of these issues.