Continuous longitudinal regression equations for pulmonary function measures

Abstract

The data from a longitudinal population study in Tucson, Arizona, were used to describe the development and decline of maximal expiratory flow-volume (MEFV) measures with age. On the basis of their answers to self-administered questionnaires, in 9 of the first 10 surveys (1972-1988) and having performed at least one MEFV test, 930 nonsmoking healthy subjects were selected, providing 3,848 individual observations. The data were analysed using statistical methods that yield continuous piecewise linear regression equations and allow subjects to have repeated measures which are unequally spaced and at different times for different subjects. In addition, the age intervals for the piecewise linear line segments are estimated for each of the MEFV indices, as part of the modelling procedure. The resulting predicted values are compared between sexes and to previously published cross-sectional results from the same population. All MEFV measures in healthy subjects have an early increase in the rate of development corresponding to the onset of the adolescent growth spurt. This rapid growth period is followed by a plateau phase which lasts around 10 yrs for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) in males, in which growth continues, but at a much lower rate. The plateau phase, is followed by a constant rate of decline which lasts throughout adulthood. In contrast, flow measures did not have a detectable plateau period, but did have points of increased rates of decline much later in life.

Evolution of exhaled nitric oxide levels throughout development and aging of healthy humans

“…Loss of alveolar elastic recoil results in increased residual volume and, as a consequence, reduced vital capacity. The reduction in forced vital capacity with age has been shown previously to be biphasic [27] and this is also indicated in our data based on NHANES subjects, with the accelerated decline starting a few years earlier in women than men. Also, the loss of static lung elastic recoil is primarily seen after age 59 years (men and women presented together), with almost no loss before that age [28].…”

“…The reduction in FVC throughout adulthood also appeared biphasic in this NHANES material, again with the breakpoint occurring earlier in females, though the breakpoint was not as clear in males as in females. Sherrill et al could also confirm a biphasic decline of FVC in women, with the breakpoint at 46 years, but could not detect any breakpoint in men using piecewise regression in a longitudinal study on 930 non-smoking healthy subjects [27]. In the same study, clear-cut breakpoints were identified in upper middle age for both women and men regarding the age-related decrease in mid-expiratory flows, whereas the reduction in FEV 1 was linear from approximately 25 years of age in this material.…”

Longitudinal methods for describing the relationship between pulmonary function, respiratory symptoms and smoking in elderly subjects: the Tucson Study

“…The following pulmonary function indices were included in the analysis: forced vital capacity (FVC), forced expiratory volume in one second (FEV 1 ), and the ratio FEVJFVC. Percentage predicted values were computed using previously published reference equations [35,36].…”