Smoking, obesity, and psychological disorders in teens may cause faster ageing in adulthood - study

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  • People age faster biologically if they smoked, were obese, or had a psychological disorder during adolescence.
  • This is according to a New Zealand study, which tracked participants over decades.
  • However, the authors noted some key limitations in their research, adding that more research is needed.

People age faster if they smoked, were obese, or had a psychological disorder – such as anxiety or depression – during adolescence, new research has found.

The researchers studied a group of people who had one of the above health conditions as a teen. They found that they aged nearly three months more per year than their peers. 

The study involved 910 people in New Zealand born in 1972 and 1973. They were part of the Dunedin Study, a long-term study that tracked participants' health and behaviour from the age of three until 45.

The findings were published in JAMA Pediatrics. The researchers wrote: “[Our] study found that adolescent smoking, obesity, and psychological disorder diagnoses were associated with older biological age at midlife. These health conditions could be treated during adolescence to reduce the risk of accelerated biological ageing later in life.”

What does slower ageing mean?

When the participants of the study turned 45, those who had two or more of the three health conditions during their adolescence walked 11.2 centimetres per second slower than those who did not. This result was after adjusting for socioeconomic disadvantages or traumatic childhood experiences.

Additionally, their brain age was two and a half years higher, and their facial age nearly four years higher than their peers.

The researchers also analysed the long-term effects of a fourth health condition, asthma. To their surprise, those who'd had asthma in their teen years – most of whom were treated – did not age biologically faster than those who hadn't. 

They wrote: "Studies have proposed that asthma accelerates ageing because of increased inflammation. However, adolescent asthma was not associated with accelerated ageing in this study."

How they measured ageing

Body mass index, waist to hip ratio, blood tests, blood pressure, cholesterol, tooth decay, periodontal disease, white blood cell count, cardiorespiratory fitness, and brain MRIs, among many other factors, were used to determine participants’ ageing.

"This adds to that past research by expanding it to these four conditions, of which we only found that three were associated with accelerated ageing," co-author, Kyle Bourassa, a clinical psychology researcher and advanced research fellow at the Durham VA Health Care System, told CNN

Bourassa said that their findings "show that these have independent effects, so each of them is exerting their own association with later ageing."

The findings

According to the researchers, there are many reasons why smoking, having a psychological disorder, and obesity can accelerate ageing.

They explain: "Smoking can directly alter the physiological functions associated with ageing, such as changes in gene expression and increased oxidative stress, which might explain why the associations between smoking and brain age exceeded those for both obesity and psychological disorders."

Oxidative stress refers to an imbalance between free radicals and antioxidants in the body. Free radicals are unstable molecules that are derived through the environment (such as smoking and pesticides) and can damage cells, causing illness and ageing.

Smoking and obesity can also play a role in increased systemic inflammation, the authors add, which has previously been found to impact ageing. 

Additionally, behavioural and environmental factors, including a lack of access to healthcare and socioeconomic disadvantage, could all be associated with accelerated ageing.

The team concluded: "The findings of this cohort study suggest that daily smoking, obesity, and/or a psychological disorder diagnosis during adolescence are associated with accelerated ageing at midlife. Treating these modifiable paediatric health conditions could prevent the accumulation of chronic disease, development of disability, and risk of early death in adulthood by reducing the risk of accelerated biological ageing."

Study limitations

The authors noted several limitations of the study, one of them being that the Dunedin Study was observational and, therefore, can't establish whether the associations were causal. 

The participants also self-identified as predominantly White and originated only from New Zealand. To support their findings, further research among diverse populations will need to take place.

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