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When studying long-term effects of alcohol consumption on health, the stability of alcohol consumption should be known. In this paper the development and stability of alcohol consumption were investigated. Seven measurements of alcohol consumption were carried out over a period of 20 years, starting at age 13 years, in a cohort of 65 men and 85 women. Effects of age, gender, and type of beverage on the stability of drinking as a dichotomous variable (drink or abstain) and on the stability of relative amounts of alcohol consumption were analyzed. The stability of the drink/abstain dichotomy was high (odds ratios >4) and increased with age. The stability of relative amounts of alcohol consumption was moderate (r[sub S] <0.6), and no effect of age was found. No sex effects were found, while the consumption of beer often showed higher stability than that of wine and spirits.Copyright © 2000 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Maximal oxygen uptake (V̇O2 max), generally accepted as a valid method for measuring state and change of aerobic fitness, was repeatedly measured in 93 males and 107 females 5 times over a period of 8 years. A direct measurement was made using a treadmill running test with constant speed (8 km/hr) and increasing slope. Oxygen uptake was analyzed continuously by an open-circuit technique. The reproducibility of V̇O2 max estimated from interperiod correlations resulted in high test-retest correlations of approximately 0.9 in both males and females. Inspection of the longitudinal data from the multiple-longitudinal design with four measurements in three cohorts did not reveal confounding effects, such as time of measurement effects, cohort effects, and drop-out effects. A comparison of the longitudinal data evaluated over four years with data from a comparable control group that was measured once during the four-year period also failed to show any testing effects, in 40% of the males and 50% of the females no leveling-off in V̇O2 max could be demonstrated; that is, there was an increase of more than 150 ml in the last stage of running. A comparison of subjects who showed leveling-off with those who showed no leveling-off supports the idea that in the age range I 2–23 years leveling-off is not a prerequisite for reaching a true V̇O2 max. Repeated measurement of V̇O2 max, using a maximal running test on a treadmill appears to be a reliable method to describe the individual development of aerobic fitness in males and females in the age range 12–23 years. [ABSTRACT FROM AUTHOR]

Aims. To investigate the relative validity of retrospectively calculated pack-years (py-retro) by comparing py-retro with prospectively calculated pack-years (py-pro). Design. A 23-year ongoing cohort study (1977-2000). Participants. One hundred and fifty-four males and females, 13 years old in 1977 and 36 years old in 2000. Setting. Amsterdam, the Netherlands. Measurements. To calculate py-pro, current smoking and quitting efforts were investigated nine times in a period of 23 years with the help of an interview or a questionnaire. At the age of 36, subjects filled out a comprehensive questionnaire about their smoking history, to calculate py-retro. Individual differences between py-pro and py-retro were calculated. In addition, Cohen's kappa was calculated after categorising py-pro and py-retro into three groups. Findings. (1) Py-retro does not under- or overestimate life-time tobacco smoking. (2) The relative validity of py-retro was moderate due to large individual differences between py-pro and py-retro. (3) The individual differences between py-pro and py-retro became larger, the higher the number of pack-years. (4) Mean difference (and 95% limits of agreement) between py-pro and py-retro was -0.039 (-5.23, 5.32) when average pack-years was <5.2 and -1.17 (-10.00, 14.65) when pack-years ≥5.2. 5. Cohen's kappa between categorized py-pro and py-retro was 0.79. Conclusions. Future researchers in the field of smoking should be aware of the moderate relative validity of py-retro. Categorizing py-retro into smoking groups results in a misclassification error that is smaller than the quantitative error in continuous py-retro, but goes together with a loss of information. [ABSTRACT FROM AUTHOR]