Assessing mobility difficulties for cross-national comparisons: results from the World Health Organization Study on Global AGEing and Adult Health

Objectives: To assess the correspondence between self-reported and measured indicators of mobility disability in older adults in six low- and middle-income countries (LMICs).

Design: Cross-sectional analysis of Study on Global AGEing and Adult Health (SAGE).

Setting: Household surveys in China, India, Russia, South Africa, Ghana, and Mexico.

Participants: Community-dwelling SAGE respondents aged 65 and older (N = 12,215).

Measurements: Objective mobility was assessed according to a 4-m timed walk at normal pace conducted in the respondent's home; slow walking speed was defined according to the Fried frailty criteria (lowest quintile of walking speed, adjusted for age and height). Self-reported mobility difficulty was assessed according to a question about ability to walk 1 km; this response was dichotomized into any versus no self-reported difficulty walking 1 km (reference no difficulty). The age- (5-year groups) and sex-specific probability of self-reporting difficulty walking 1 km was estimated in those with a measured slow walk using logistic regression.

Results: Between 42% and 76% of people aged 65 and older reported any difficulty walking 1 km. Average walking speed was slowest in Russia (0.61 m/s) and fastest in China (0.88 m/s). The probabilities of reporting any difficulty walking 1 km in women aged 65 to 69, for example, with a slow walk varied (China = 0.35, India = 0.90, Russia = 0.68, South Africa = 0.81, Ghana = 0.91, Mexico = 0.73; test of country differences P < .001). There was significant variation at older ages, albeit smaller in magnitude. Patterns were similar for men.

Conclusion: Although correspondence between an objective and self-reported measure of mobility was generally high, correspondence differed significantly between LMICs. International comparisons of self-reported disability measures for clinical, prevention, and policy guidelines in LMICs should consider that self-reported data may not correspond to objective measures uniformly between countries.