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Interrelationships of peak expiratory flow rate with physical and cognitive function in the elderly: MacArthur
N R Cook1, M S Albert, L F Berkman
1Department of Medicine, Brigham and Women's Hospital, USA.
Background:
Peak expiratory flow rate (PEFR) is correlated with several measures of health in the elderly, including physical and cognitive function. It is unclear, however, whether these relationships persist among the non-frail.
Methods:
The Community-based Studies of the MacArthur Foundation Research Network on Successful Aging included measures of PEFR using a mini-Wright peak flow meter on a sample of 1,354 subjects selected from those aged 70-79 in three population samples. Subjects were chosen on the basis of simple measures of physical and cognitive function (high = 1192; medium = 80; low = 82), and were given a series of more detailed tests.
Results:
Residual PEFR, adjusted for age, sex, height, weight, and smoking, was highly correlated (p < .001) with several physical performance measures, including number of steps in a tandem walk, number of seconds in a single leg stand, times to turn in a circle, write one's name, and walk 10 feet at a fast pace, foot-tapping (time per tap), and hand grip strength. The strongest association was evident for a combination of six physical function items. Residual PEFR was also correlated with cognitive performance, including tests of similarities, naming, spatial recognition, memory, and figure drawing. The strongest association was present for a combined measure. These associations persisted in analyses restricted to those in the "high" function group as well as with no history of previous myocardial infarction, stroke, or cancer. Residual PEFR also exhibited a strong independent association with urinary norepinephrine, as measured in 12-hour overnight urine specimens. This relation did not appear to be mediated by smoking or medication use.