Swapping TV for a book while sitting could reduce dementia risk

New world-first research has found replacing passive activities with mentally engaging ones while sitting could reduce the risk of dementia onset in later life.

Most adults spend about nine to 10 hours per day sitting. Previous research has shown that extended, uninterrupted sitting is a risk factor for cardiovascular disease, type 2 diabetes, and depression. It has also been associated with dementia.

Globally, populations are ageing. Dementia is the third highest cause of mortality and the seventh largest cause of disability among older adults around the world. It is a prevalent age-related condition affecting many adults’ quality of life, including their families and carers. Prevention is important, and a key part of this involves identifying modifiable risk factors.

Previously, all sedentary behaviours were associated with a higher risk of developing dementia. However, new research has found that mentally passive sedentary behaviours (such as watching TV, listening to music, or sitting in the bathtub) increased the risk of depression, while mentally active sedentary behaviours (such as reading, office work, or knitting) appeared to be protective.

The study – which involved researchers from the Baker-Deakin Department of Lifestyle and Diabetes, the Deakin Institute for Physical Activity and Nutrition, the University of São Paulo, Brazil, and the Karolinska Institute in Sweden – is the first to investigate the link between passive and active sitting and dementia.

Professor David Dunstan, Head of the Baker-Deakin Department of Lifestyle and Diabetes and a co-author on the study, says the findings could potentially inform public health guidelines and preventive strategies to reduce dementia.

‘While sitting is always physically inactive, we can still be exercising our brains, which can offset some of the damage sitting causes,’ Professor Dunstan says.

‘This is also good news for office workers too, who by necessity sit for long periods at a desk. Now we know that, simply by undertaking the daily tasks required by their jobs, they are helping to stimulate their minds and create that welcome protective effect.'

Researchers analysed data from a longitudinal study of 20,811 adults aged 35–64 years followed over 19 years (1997–2016). The baseline survey included questions about sedentary behaviours, physical activity and other behaviours associated with dementia. Incident dementia was identified by linking the data of the 1997 survey with the Swedish National Patient Register and the Swedish Cause of Death Register.

The study, recently published in the American Journal of Preventive Medicine, also found there was no need to completely give up traditionally sedentary activities like watching television, provided that a person engages in an equal amount of mentally stimulating activity each day. 

Given the extensive survey method used to collect these data (3,600 cities and villages across Sweden), the investigators believe the findings could be applied across a wider global population.

Professor Dunstan says, ‘Long periods of inactivity are a common risk factor for many health conditions, but one that can be easily changed. Our study shows we shouldn’t be lumping all sitting into one category; some may increase the risk of dementia, while others may be protective.

‘It is important to remain physically active as we age, but also mentally active — especially when we are sitting.’