Abstract
Damage accumulation is widely accepted as the central dogma of ageing, and it has been a long-standing belief that tobacco smokers must experience a faster rate of ageing than non-smokers. It is therefore puzzling as to why proportional hazard model is a popular choice in longitudinal studies given that its assumption assumes a constant hazard with increasing time. If the rate of ageing is accelerated, the hazard gradient of smokers d(log(μ(x)))/dx obtained from frailty parametric fit has to be steeper than non-smokers. This study examines the relative derivative for mortality d(log(μ(x)))/dx of British doctors born 1900–1909, and obtained estimates indicate that the rate of ageing is similar between smokers and non-smokers. A brief theorem is also elaborated to present the difference in life-years gained from interventions and policies by life-detrimental risk exposure; e.g. smokers 0.8; non-smokers 5.3 mins/day. The controversial assumption made in the central dogma of ageing, heterogeneity axiom and the application of proportional hazard models are unveiled in this condensed parametric analyses.
Highlights
Many previous studies have shown that tobacco smoking is associated with an increased risk for chronic health diseases such as breast cancer, myocardial infarction and dementia[1,2,3]
To examine whether tobacco smokers experience (I) a higher magnitude for mortality risk log μ(x); (II) a faster rate of ageing d(log(μ(x)))/dx; (III) both mortality risk and rate of ageing are elevated to non-smokers; the age-specific mortality trajectory of British doctors born in year 1900–1909 is presented by fitting a parametric model to determine the shape and pace of the hazard of smokers and non-smokers; Supplementary Table S1
As the findings demonstrate the human rate of ageing does not differ by smoking behaviour, selection for mortality which outlines the frailty distribution is likely to be solely dependent on magnitude for mortality risk than our previously presumed central dogma - the rate of ageing
Summary
Many previous studies have shown that tobacco smoking is associated with an increased risk for chronic health diseases such as breast cancer, myocardial infarction and dementia[1,2,3]. There has not been a fundamental reason to raise the hypothesis that the rate of ageing among smokers is not accelerated. This central dogma contradicts the popular statistical choice for proportional hazard models in longitudinal studies, in prospective studies. If damage accumulation from tobacco smoking accelerates the rate of ageing and increases the risk for mortality, the relative risk for mortality between smokers and non-smokers will diverge with increasing age. Proportional hazard models which assume a constant hazard risk with increasing age will be void, i.e. a constant hazard is equivalent to parallel hazard lines between log μ(x)exposed and log μ(x)non-exposed group with increasing age
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
