Comparing survey data on functional disability: the impact of some methodological differences

Area of Science:

• Gerontology
• Epidemiology
• Survey Methodology

Background:

• Prevalence of functional disability in the elderly is crucial for public health planning.
• Existing population-based surveys may yield varying disability estimates due to methodological differences.

Purpose of the Study:

• To assess how variations in survey methods influence functional disability prevalence in elderly populations.
• To quantify the impact of data collection and questionnaire design on disability estimates.

Main Methods:

• Comparison of nine population-based surveys of Dutch individuals aged 55+.
• Analysis of data collection methods (proxy vs. direct, interview vs. self-administered) and questionnaire design (wording, response categories).
• Application of univariate and multivariate logistic regression to determine methodological effects on activities of daily living, mobility, and communication disability.

Main Results:

• Proxy questioning showed no significant effect on disability prevalence.
• Self-administered questionnaires resulted in higher disability prevalence, particularly for mobility (OR 1.4) and communication (OR 1.7).
• Substantial prevalence differences (up to 15.6 percentage points) were observed due to minor questionnaire wording and structure variations, linked to disability severity.

Conclusions:

• Survey methodology exerts a considerable influence on functional disability prevalence estimates in the elderly.
• Methodological variations necessitate careful consideration for international comparisons and longitudinal trend analyses of disability data.