Factors associated with non-participation in the Healthy Cognitive Ageing Project

Understanding cognitive decline trajectories is crucial for dementia prevention, as many cases go undetected. Identifying participation biases in such studies is essential for data validity.

We examined non-participation correlates in the Healthy Cognitive Ageing Project (HCAP), a sub-study of the English Longitudinal Study of Ageing (ELSA). We compared sociodemographic and health characteristics of invited, interviewed, and non-interviewed individuals, and assessed the impact of sample weights.

Of 1778 ELSA members invited in 2018, 1273 (72%) participated. Participants were similar to the invited sample in sociodemographics but were younger, had fewer daily living difficulties, and had better cognition. Non-participation was linked to difficulties in daily living (odds ratio 1.78), dementia (1.55), and psychiatric conditions (1.34). Weighted analyses highlighted differences in disability and cognition.

Non-participation in cognitive studies is not random, lowering response and retention rates, and requiring adjustments to data analysis beyond the use of weights.

We compared the sociodemographics of invited, interviewed, and non-interviewed individuals. We used sample weights to assess differences in participants' characteristics. We found non-participation linked to daily living difficulties, dementia, and psychiatric conditions.