The Nottingham Longitudinal Study of Activity and Ageing: A Methodological Overview

OBJECTIVES: first, to describe the background and methodological approach to the assessment of customary physical activity, health and psycho-social status used by the Nottingham Longitudinal Study of Activity and Ageing; second, to provide information on the sampling strategy and survey response rates for three waves of data collection; and, third, to provide information on the reliability and validity of the survey assessments. DESIGN: longitudinal study. SUBJECTS: 1042 people originally aged 65 and over, randomly sampled from general practitioner lists in Nottingham, UK. METHODS: a descriptive overview of response rates (%), instrument reliability (alpha coefficients) and intercorrelations among measured outcomes (correlation coefficients and principal components analysis). MAIN OUTCOME MEASURES: questionnaire-assessed levels of physical activity; instrumental measurements of handgrip strength, weight, demi-span and shoulder flexibility; brief assessments of depression, social engagement, life-satisfaction and cognitive impairment. RESULTS: the study achieved a baseline (TI) response rate of 80%, with re-interview rates of 88% and 73% for T2 (1989) and T3 (1993) surveys respectively. For both men and women, factor scores derived from first principal components extracted from T1 survey data showed significant (r > or = 0.4; P or = 0.7).