Sir,
I went through with interest the article entitled “Incidence and factors associated with medication nonadherence in patients with mental illness: A cross-sectional study” published in the “Journal of Postgraduate Medicine” (2015; 16:251-6).[1]
The authors have conducted a cross-sectional study in the outpatient psychiatric department of a tertiary care private hospital over a period of 1 year and followed up the patients receiving at least one psychotropic medication for at least 1 month. The authors concluded that the overall incidence of medication nonadherence in patients with mental illness was 43%. I have concerns regarding the calculation of incidence for which reference to time is important.[2]
The authors have actually provided us with an estimate of the proportion of nonadherence among patients on psychotropic medication and not incidence. As incidence involves a reference to time; it is not expressed as a percentage (as done by the authors) but as person-time.[3] In contrast, the proportion in statistics refers to the fraction of the total that possesses a certain attribute such as nonadherence in case of this study.
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References
- 1.Lucca JM, Ramesh M, Parthasarathi G, Ram D. Incidence and factors associated with medication nonadherence in patients with mental illness: A cross-sectional study. J Postgrad Med. 2015;61:251–6. doi: 10.4103/0022-3859.166514. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Szklo M, Nieto FJ. Measuring disease occurrence. In: Szklo M, Nieto FJ, editors. Epidemiology Beyond the Basics. 2nd ed. Sudbury, MA: Jones and Bartlett Publishers, Inc; 2007. pp. 47–76. [Google Scholar]
- 3.Raina SK. Incidence of malignancies in biopsy-proven inflammatory myopathy: Comment and erratum. Neurol India. 2013;61:340. doi: 10.4103/0028-3886.115104. [DOI] [PubMed] [Google Scholar]