Does the 15-item Geriatric Depression Scale function differently in old people with different levels of cognitive...

Area of Science:

• Geriatric Psychiatry
• Psychometrics
• Cognitive Neuroscience

Background:

• The 15-item Geriatric Depression Scale (GDS-15) is a common depression screening tool for the elderly.
• Its performance in individuals with cognitive impairment compared to cognitively normal individuals is not well understood.
• Investigating Differential Item Functioning (DIF) is crucial for ensuring scale fairness across different cognitive groups.

Purpose of the Study:

• To investigate Differential Item Functioning (DIF) of the GDS-15 in older adults with varying cognitive functioning levels.
• To apply Item Response Theory (IRT)-based analyses to compare scale functioning between cognitively normal and impaired groups.

Main Methods:

• Utilized data from a large Italian multi-centric study (N = 1903) of cognitive impairment and dementia in older adults.
• Participants were categorized into three groups based on cognitive functioning: normal, mild cognitive impairment, and cognitive impairment.
• Item Response Theory (IRT) analyses were performed to detect DIF across these cognitive groups.

Main Results:

• Two specific items on the GDS-15 exhibited uniform Differential Item Functioning (DIF).
• However, the DIF observed in these items did not significantly impact the overall GDS-15 total scores.
• The differential functioning did not necessitate a separate interpretation of the total scores across cognitive groups.

Conclusions:

• The findings support the continued clinical utility of the GDS-15 as a depression screening tool for the elderly.
• The scale demonstrates acceptable functioning across different cognitive statuses, including mild cognitive impairment and cognitive impairment.
• The GDS-15 can be reliably used for screening depression in the general elderly population, irrespective of cognitive status.