The World Health Organization ageism towards older persons scale: preliminary validation of a novel measure of ageist stereotypes, prejudices, and discrimination in four different countries.

A 10-item one-factor model was identified as the final structure of the WHO-A-TOPS through an iterative development process.

• The scale captures all three dimensions of ageism: stereotypes, prejudices, and discrimination.
• The iterative process resulted in reduction to 10 items from the initial item pool.
• The one-factor structure indicates ageism is captured as a single underlying construct.
• Data were collected from 1778 participants aged 20-90 years across four countries.

The WHO-A-TOPS demonstrated acceptable partial scalar measurement invariance across four countries (Czech Republic, Germany, Israel, and the United Kingdom).

• Partial scalar invariance (rather than full scalar invariance) was achieved across countries.
• The finding indicates the measure can capture a common construct across the four investigated countries.
• The four countries represent diverse national and cultural contexts for validation.
• Total sample size was 1778 participants.

The WHO-A-TOPS demonstrated measurement invariance across different age groups.

• Invariance was established across three age groups within the sample aged 20-90 years.
• This indicates the scale can be used comparably across younger and older respondents.
• Age group invariance supports the tool's utility for studying ageism across the lifespan.
• The finding is notable as ageism research often targets specific age cohorts.

The WHO-A-TOPS demonstrated acceptable internal consistency as part of its psychometric validation.

• Internal consistency was evaluated alongside structural validity, measurement invariance, and construct validity.
• The scale was validated following current state-of-the-art psychometric guidelines.
• The study described the tool as representing 'an exceptional attempt to develop a measure of high psychometric properties.'
• Construct validity was also assessed as part of the preliminary validation process.

The study identified complexities in achieving full measurement invariance across countries when measuring ageism.

• Only partial scalar invariance (not full scalar invariance) was achieved across the four countries.
• This finding highlights 'the complexities of measuring ageism's multifaceted nature' across cultural contexts.
• Cross-country differences in ageist attitudes may account for some non-invariance.
• The authors noted implications for cross-country comparisons in ageism research.