Choosing controls.

Sir,

Went through with interest article entitled “Perceived caregiver stress in Alzheimer's disease and mild cognitive impairment: A case–control study” published in Ann Indian Acad Neurol (2016;19:58-62).[1] The authors deserve credit for highlighting an important area of concern in patient management.

However, I have a concern. The authors conducted the present study in a case–control study design mode with caregivers of patients diagnosed with Alzheimer's disease/mild cognitive impairment (AD/MCI) identified as cases while the controls included caregivers of patients with chronic medical and psychiatric disorders.[1] Accordingly, a total of 31 patients of AD/MCI (males = 24, females = 7), and 30 controls (males = 18, females = 12) were interviewed. On the basis of this, the authors conclude that caregivers of patients with AD/MCI have a high perceived stress compared to caregivers of patients with other chronic illness. Now, this is where my primary concern lies. Agreed that the study being a hospital-based case–control study and choosing suitable hospital controls is often difficult, but choosing the right controls is perhaps the most important step in a case–control study.[2] Herein, the authors have chosen controls which may not be similar to cases in variables (other than the variable of interest), which is a fundamental principle of case–control studies. This is clearly apparent in Table 1 of the study (reproduced below). The mean age for caregivers of AD/MCI (cases) was 69 ± 11.86 years while for caregivers of chronic disorders it was much less at 56 ± 5.53 years. Similarly, the mean duration of illness was higher in AD/MCI as compared to caregivers of chronic disorders (controls). Other parameters which influence perceived stress including gender and social status has not been dealt with by the authors.

Table 1

Variables among caregivers of Alzheimer's disease/mild cognitive impairment and chronic disorders

Further, it is known fact that caregivers of individuals with dementia suffer from caregiver burden more frequently than other caregiver groups and are more vulnerable for various health problems.[3] Therefore, matching for factors associated with caregiver burden such as the sociodemographic status of the caregiver and care recipient, the nature of the disease of the care-recipient, etc., assumes importance.

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