Figure 1.

Flow chart illustrating how the total cohort of Newcastle 85+ Study participants was subdivided in the respiratory study sample, demonstrating why different numbers of participants are included in the analyses. The derivation of the study groups are shown in the flow chart; note that for some variables the number of participants included is less than 845 due to missing data, the reasons for which are detailed. The basis for the healthy reference group (HRG) was the 845 participants who had multidimensional health assessment (MDHA) and general practice records review (GPRR) conducted. Of these, 786 (93.0%) had spirometry performed of whom 772 performed it adequately; a further 35 participants with missing demispan were removed (unable to calculate predicted blows), resulting in 737. Participants with at least one respiratory condition, those with respiratory symptoms and those on respiratory medication were excluded which reduced the group size to 170. Other conditions which have an effect on spirometry values were also taken into account leading to exclusion of a further 19 participants. The remaining 151 (17.9% of 845) participants formed the HRG.