Heavy smoking and alcohol use cause distinctive changes to human DNA, leading to an accelerated premature ageing, scientists reveal.
Interestingly, moderate alcohol use -- about one to two drinks per day -- was correlated with the healthiest ageing, while very low and high consumption were linked to accelerated ageing.
Biological ageing is the progressive decline in physiological ability to meet demands that occurs over time.
It is due to the accumulation of damage at the cellular level and the rate of biological ageing is determined by both environmental and genetic factors.
While calculating the difference between biological age and chronological age, the researchers found that all levels of exposure to smoke were associated with significantly premature ageing.
Using data from the publicly available "Gene Expression Omnibus", Robert A Philibert from University of Iowa analysed patterns of DNA methylation - a molecular modification to DNA that affects when and how strongly a gene is expressed.
Prior research had shown that methylation patterns change in predictable ways as people age as well as in response to cigarette smoke and alcohol.
"Being able to objectively identify future smokers and heavy alcohol users when they are young can help providers and public health practitioners improve quality of life and reduce medical costs," Dr Philibert emphasised.
The next step is to unravel the details of how methylation patterns change in response to lifestyle changes during the life course so that their assessments can be more informative.
The findings were presented at the American Society of Human Genetics (ASHG) 2015 annual meeting in Baltimore this week.
