A latent variable approach to studying risk factors for Alzheimer's disease

The objective of this study is to investigate and to improve measurements f or the study of suspected animal and occupational exposure risk factors for Alzheimer's disease (AD). A subsample (n = 200) of a longitudinal study sa mple from research on risk factors for Alzheimer's disease was selected by systematic probability sampling. Participants were men born between 1917 an d 1927, selected from the National Academy of Sciences-National Research Co uncil (NAS-NRC) Registry of white male twins who served in the United State s Armed Forces during the World War II Korean Conflict era. A questionnaire was administered via telephone interview. A total of 25 animal exposure it ems and 28 occupational exposure items were selected from the risk factor q uestionnaire administered to the men. Measurement for animal or occupationa l exposure was ascertained based upon the participants' responses to the su rvey questions. Latent variable analyses extracted 3 animal exposure factor scales: pet, farm/livestock and exposure to wild animals (e.g, while hunti ng). The occupational exposure data led to extraction of 2 factor scales: m edical exposures and manual work involving metal. Latent variable analysis revealed that many items (potential risk factors) are highly correlated wit h each other and can be conceptualized as correlated observable manifestati ons of more unitary underlying constructs. In future research, it may be ad vantageous to assess correlated items such as these in relation to an under lying dimension of exposure, rather than as discrete exposures. Copyright ( C) 2001 S. Karger AG, Basel.