Smoking may be the key lifestyle factor that determines how quickly cognitive decline occurs in older adults, research suggests.

Memory and fluency in older adults declined by up to 85% more over a 10-year period in smokers compared to non-smokers.

The study, which was undertaken by researchers at University College London (UCL), looked at 16 different lifestyle factors, including physical activity, alcohol consumption and social contact, and concluded that smoking had the most significant impact on cognitive decline.

The findings are published in Nature Communications.

The global population is ageing, and associated ageing-related neurodegenerative conditions such as dementia have become an increasing public health concern. Modifiable lifestyle factors which may play a role in delaying cognitive decline are therefore increasingly important to understand.

The researchers analysed data from 32,033 cognitively healthy adults between the ages of 50 and 104. All the participants were part of prospective cohort studies of ageing in 14 European countries, including data from the English Longitudinal Study of Ageing (ELSA) and the Survey of Health, Ageing and Retirement in Europe (SHARE).

Different lifestyle choices were analysed alongside cognitive decline over 10 years.

These included whether people were smokers or non-smokers, whether they exercised moderately or vigorously at least once a week, how often they saw family or friends and how much they drank per week.

Cognitive function was assessed according to participants’ memory and verbal fluency test performance.

In addition, the researchers accounted for various factors that might have influenced the findings, including age, gender, country, education, wealth, and chronic conditions.

Memory and fluency decline were generally similar for people with a non-smoking lifestyle but were found to decline by up to 85% more over 10 years for participants who were smokers compared with non-smokers.

The researchers concluded that differences in cognitive decline between lifestyles were primarily dependent on smoking status.

Lead author Dr Mikaela Bloomberg from UCL said: ‘Previous evidence suggests individuals who engage in more healthy behaviours have slower cognitive decline; however, it was unclear whether all behaviours contributed equally to cognitive decline, or if there were specific behaviours driving these results.

'Our findings suggest that among the healthy behaviours we examined, not smoking may be among the most important in terms of maintaining cognitive function.’

The researchers noted that the study was observational and could not definitively establish cause and effect; however, the findings suggest that ‘smoking could be a significant factor influencing the rate of cognitive ageing.’

The only exception to the findings were smokers who otherwise had a healthy lifestyle, such as regular exercise, moderate alcohol consumption and regular social contact. The rate of cognitive decline in this group of participants was found to be similar to that of non-smokers.

Dr Bloomberg added: ‘For people who aren’t able to stop smoking, our results suggest that engaging in other healthy behaviours such as regular exercise, moderate alcohol consumption and being socially active may help offset adverse cognitive effects associated with smoking.’

This article was first published by our sister title Nursing in Practice