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 psyche-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 (cr 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 greater than or equal to 0.4; P< 0.001) product moment correlations with instrumental measurements of handgrip strength and shoulder flexibility. All the brief assessment measures showed satisfactory levels of reliability (alpha greater than or equal to 0.7).