Statistical concerns about the study: “Risk factors for polypharmacy in older adults in a primary care setting: a cross-sectional study”
Kubra Aydin,1 Meryem Merve Oren,2 Tugba Aydin3
1Ataturk University School of Medicine, Department of Internal Medicine, Division of Nephrology, Ataturk University, Yakutiye 25100, Erzurum, Turkey; 2Istanbul University, Istanbul Medical School, Department of Public Health, Capa 34390, Istanbul, Turkey; 3Istanbul Physical Medicine and Rehabilitation Training Hospital, Department of Physical Therapy and Rehabilitation, Bahcelievler 34188, Istanbul, Turkey
We read the article by Ersoy and Engin on the risk factors for polypharmacy in older adults in a primary care setting with great interest.1 We would like to add some comments that should improve the data interpretation in this large study.Firstly, the authors noted that they assessed functionality by Activities of Daily Living and Instrumental Activities of Daily Living scales (ADL and IADL) with ADL consisting of five self-care measures, and IADL consisting of seven tasks. Scoring isundertaken using a 3-point ordinal scale, ranging from 0 to 2. The 0 point indicates inability, 1 indicates ability to do the task with aid, and 2 indicates ability to do it independently. The maximum score is 10 for the ADL and 14 for the IADL. The authors referred to the articles by Katz et al in 1963 and Lawton and Brody in 1969.2,3 However, Katz et al and Lawton and Brody’s assessments were not evaluated with five and seven items, respectively, and they did not use the 0–2 scale in the referenced articles.2,3 Instead, in the mentioned articles, ADL and IADL were assessed by six and eight items, respectively. Katz et al used an A to G scale to evaluate ADL and Lawton and Brody used a 0–1 scale to evaluate IADL. Accordingly, the maximum scores were not 10 and 14 but A (Katz et al for ADL) and 8 (Lawton and Brody for IADL), respectively. Furthermore, to our knowledge, the method the authors applied for evaluation of ADL and IADL has not been validated, yet. Thus, the methodology they used to assess ADL and IADL should be clarified and noted as limitation of the study. Secondly, some statistical flaws were observed. The authors stated that they used Pearson correlation test to assess association between daily drug consumption (DDC) and continuous variables. However, the mean DDC was given as 4.63±3.51, with a very high SD value. This most probably suggests that the DDC parameter was a non-homogeneously distributed parameter. Hence, instead of Pearson correlation coefficient, Spearman Rho correlation should have been used. Similarly, while assessing the association between DDC and categorical variables such as presence of diabetes mellitus, metabolic syndrome, etc (as DDC seemed to be a non-homogenous parameter), the analyses should have been performed by Mann–Whitney U test instead of Student’s t-test.4–7
View the original paper by Ersoy and Engin.
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