JMIR Publications

ABSTRACT

Background:

Reducing the number of items in a questionnaire while maintaining relevant information is important as it is associated with advantages such as higher respondent engagement and reduced response error. However, in healthcare, after the original design, an “a posteriori” check of the included items in a questionnaire is often overlooked or considered of minor importance. When it is conducted, it is often based on a single selected method. We argue that, before finalizing any lifestyle questionnaire, “a posteriori” validations should always be conducted using multiple approaches to ensure robustness of the results.

Objective:

The objectives of this study were to compare the results of two statistical methods for item reduction (Variance Inflation Factor [VIF] and Factor Analysis [FA]) in a lifestyle questionnaire constructed by combining items from different sources, and to analyse the different results obtained from the two methods and the conclusions that can be made about the original items.

Methods:

Data were collected from 79 participants (heterogeneous in age and sex) with a high risk of metabolic syndrome, working in a financial company based in Tokyo. The lifestyle questionnaire was constructed by combining items (asked with daily, weekly, and monthly frequency) from multiple validated questionnaires and other selected questions. Item reduction was conducted using VIF and exploratory FA. Adequacy tests were employed to check data distribution and its sampling adequacy.

Results:

Among daily and weekly questions, both VIF and FA identified redundancies in sleep-related items. Among monthly questions, both approaches identified redundancies in stress-related items. However, the number of items suggested for reduction often differed: VIF suggested larger reductions than FA for daily questions, but fewer reductions for weekly questions. Adequacy tests always confirmed that structure detection was adequate for the considered items.

Conclusions:

As expected, our analyses showed that VIF and FA produce both similar and different findings, suggesting that questionnaire designers should consider using multiple methods for item reduction. Our findings using both methods indicate that many questions, especially those related to sleep, are redundant, indicating that the considered lifestyle questionnaire can be shortened. Clinical Trial: Not applicable.