Research by scientists at the University of Edinburgh to examine environmental factors that might cause dementia found that the people who lived in areas with higher levels of aluminium in the drinking water were more likely to die from the illness.
The study involved around 7,000 individuals born in 1921 who undertook an intelligence test in 1932 which was the forerunner of the historical 11-plus exam. A total of 1,972 out of 6,990 participants in the study had developed dementia by 2012.
A north/south divide in Scotland in the quality of drinking water was also revealed, with the North East coming out worst and the Borders and South West coming out on top.
Coagulants such as alum (aluminium sulphate) are used to trap impurities in raw water by binding them together to form particles before they are filtered out.
Fluoride occurs naturally and is not added to the water supply in Scotland. Researchers say there is some evidence that it increases the human absorption of aluminium.
Study author, Dr Tom Russ from the Alzheimer Scotland Dementia Research Centre at the University of Edinburgh, stressed that the low levels of aluminium and fluoride found in the water in Scotland were “very good” in relation to World Health Organisation guidelines.
“Everybody included in the study was alive in 2005 and they were all born in 1921,” he said. “Everybody who subsequently died with dementia was compared with those who died without, and the people who lived in areas of higher levels of aluminium in drinking water were more likely to die than those in areas where the aluminium levels were lower.
“We still see this well accepted finding that higher levels of aluminium in particular are associated with an increased risk of dementia. It’s confirmatory rather than anything else.”
The study published in the British Journal Of Psychiatry, obtained water quality data from the Drinking Water Quality Regulator for Scotland for the years 2005-2014. The DWQR is responsible for regulating public water supplied by Scottish Water, which was established in 2002. Prior to this water quality was the responsibility of separate local authorities.
A Scottish Water spokesperson said: “Scottish Water, like other UK water companies, operates in a highly regulated industry where public health is the prime concern and delivering high quality drinking water to customers across Scotland is a key priority for us.
“We carried out over 311,000 tests in 2017 at customer taps, our service reservoirs and treatment works to ensure customers receive consistently high quality drinking water and more than 99.91 per cent of tests at customer taps passed stringent quality standards.”