Abstinence from alcohol in middle age has been linked to a heightened risk of dementia, a new study suggests.
Both people who drink over the recommended limits and those who are teetotal in midlife are at an increased risk, researchers found.
A new study, published in the British Medical Journal (The BMJ), examined data on more than 9,000 people taking part in the Whitehall II study - which tracked the health of civil servants working in London.
The participants were aged between 35 and 55 when the study began in the mid 1980s.
Alcohol consumption was measured during assessments between 1985 and 1993, when the participants had an average age of 50.
They were followed up for an average of 23 years, with cases of dementia identified through hospital, mental health services, and mortality records. A total of 397 cases of dementia were recorded.
Abstinence in midlife was associated with a 45% higher risk of dementia compared with people who consumed between one and 14 units of alcohol per week.
Long term abstainers and those who reported a decrease in alcohol consumption also appeared to have an increased risk.
The team of French and British researchers suggested that part of the excess risk of dementia in abstainers could be attributable to the greater risk of cardiometabolic disease reported in this group.
Among excessive drinkers - those who consumed more than 14 units per week - experts found a heightened risk of dementia which increased the more a person drank - they noted that with every 7-unit/week increase there was a significant 17% increase in dementia risk.
"These results suggest that abstention and excessive alcohol consumption are associated with an increased risk of dementia, although the underlying mechanisms are likely to be different in the two groups," the authors wrote.
Guidance from the UK chief medical officer states that men and women should drink no more than 14 units of alcohol each week - the equivalent of six pints of average strength beer.
Commenting on the study, Dr Sara Imarisio, head of research at Alzheimer's Research UK, said: "As this study only looked at people's drinking in midlife, we don't know about their drinking habits earlier in adulthood, and it is possible that this may contribute to their later life dementia risk.
"People who completely abstain from alcohol may have a history of heavy drinking and this can make it difficult to interpret the links between drinking and health.
"Future research will need to examine drinking habits across a whole lifetime, and this will help to shed more light on the relationship between alcohol and dementia."
She added: "Current alcohol guidelines recommend not regularly drinking more than 14 units a week for both men and women, and drinking over this amount impacts on a number of health conditions, not only dementia.
"We know that a healthy lifestyle, including cutting down on too much alcohol, can improve health and reduce dementia risk, and a good motto tends to be, what is good for your heart is good for your brain.
"Not smoking, eating a healthy balanced diet, staying mentally and physically active and keeping blood pressure and cholesterol in check are all ways to support healthy brain ageing."
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