The Impact of Attrition in an 11-Year Prospective Longitudinal Study of Younger Women

Purpose

To investigate the impact of attrition on prevalence and associations between variables across four waves of a longitudinal study.

Methods

Prevalence of socio-demographic and health characteristics were estimated for respondents to one, two, three or all four waves of the Australian Longitudinal Study of Women's Health cohort born between 1973 and 1978. Associations with self-rated General Health (GH) and Mental Health (MH) were compared using fixed effects in separate mixed models for respondents to at least one wave, at least two waves, at least three waves, or four waves of the longitudinal study.

Results

14,247 women aged 18-23 years responded to Wave 1 in 1996. Respondents to all waves were more educated, and less likely to be stressed about money, to be smokers and to have children than respondents to some waves. Across all models, better GH was consistently associated with more education, no monetary stress, being married, having children, fewer visits to the doctor and not smoking. Similar results were obtained for MH.

Conclusions

Although the potential for bias due to attrition must be considered, the current paper contributes to the growing body of evidence that suggests such biases are insufficient to preclude meaningful longitudinal analyses.

Key Words: Bias, Dropouts, Longitudinal Studies