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<i>Aim:</i> To assess longitudinally whether smoking tobacco is related to muscle strength in healthy adults and to assess the influence of lifestyle covariates on this relation. <i>Methods:</i> Data were obtained from the observational Amsterdam Growth and Health Longitudinal Study, with four repeated measurements at the ages of 21 (n = 181), 27 (n = 144), 32 (n = 426) and 36 (n = 373) years. Knee muscle strength (KMS) was measured at an angle of 300° per second. Smoking and the covariates physical activity and dietary intake were assessed with a questionnaire. Other covariates included physical fitness and body fat percentage. Cardiopulmonary fitness was assessed with a maximal running test and body fatness with skinfold measurements. Sex-specific longitudinal analyses were carried out using generalized estimating equations. <i>Results:</i> In men and women, an inverse relationship between smoking tobacco and KMS was found. Smoking 100 g of tobacco a week resulted in a reduction of 2.9% in KMS in men and a reduction of 5.0% in women. This relation existed largely independently of lifestyle covariates.<i> Conclusion:</i> This study indicates that smoking is inversely related to skeletal muscle strength in healthy adults.

The purpose of this study was to investigate the agreement between self-reported tobacco consumption and NicCheck 1^® (Dynagen Inc. Cambridge, Mass., USA) regarding smoking status and nicotine intake in a population of smokers (20.8%) and non-smokers. NicCheck 1 is a dipstick that changes colour in the presence of urinary nicotine metabolites. Smoking was assessed by self-report and NicCheck 1 in 169 males and 191 females (mean age 36.0 SD 0.7). Self-report and NicCheck 1 agreed highly on smoking status, especially in moderate to heavy smokers. With regard to nicotine intake, there was a large overlap in self-reported tobacco consumption between NicCheck 1 levels, despite a relatively high correlation coefficient between self-report and NicCheck 1 in smokers (i.e. 0.74). No effect modification by gender or BMI was found. When both methods were validated against two blood lipid parameters, self-report seemed to do equally well as NicCheck 1 in assessing nicotine intake.

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_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.

Previous studies have discouraged the use of the Cox proportional hazards (PH) model for traditional mediation analysis as it might provide biased results. Accelerated failure time (AFT) models have been proposed as an alternative for Cox PH models. In addition, the use of the potential outcomes framework has been proposed for mediation models with time‐to‐event outcomes. The aim of this paper is to investigate the performance of traditional mediation analysis and potential outcomes mediation analysis based on both the Cox PH and the AFT model. This is done by means of a Monte Carlo simulation study and the illustration of the methods using an empirical data set. Both the product‐of‐coefficients method of the traditional mediation analysis and the potential outcomes framework yield unbiased estimates with respect to their own underlying indirect effect value for simple mediation models with a time‐to‐event outcome and estimated based on Cox PH or AFT.