|Year : 2016 | Volume
| Issue : 1 | Page : 51-52
Calculating incidence in cross-sectional studies
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Himachal Pradesh, India
|Date of Web Publication||5-Jan-2016|
S K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Himachal Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raina S K. Calculating incidence in cross-sectional studies. J Postgrad Med 2016;62:51-2
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). 
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. 
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.  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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Conflicts of interest
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| :: References|| |
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.
Szklo M, Nieto FJ. Measuring disease occurrence. In: Szklo M, Nieto FJ, editors. Epidemiology Beyond the Basics. 2 nd
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Raina SK. Incidence of malignancies in biopsy-proven inflammatory myopathy: Comment and erratum. Neurol India 2013;61:340.