Statins are not effective at reducing heart disease and stroke among certain groups of elderly people, a new study suggests.
The findings "do not support the widespread use of statins in old and very old populations", the authors wrote.
But the cholesterol-lowering drugs, which are widely prescribed across the globe, are supported among some groups, they said.
However, other experts called into question whether the study's conclusions were appropriate.
The new study, published in The British Medical Journal, set out to assess whether statin treatment is associated with a reduction in cardiovascular disease and death in old - classed as 75-84 years - and very old - people who are 85 years and over - with and without type 2 diabetes.
A team of Spanish researchers analysed data on almost 47,000 people, with an average age of 77, included in the Catalan primary care system database between 2006 and 2015.
The participants were followed up for an average of 5.6 years to see whether they developed cardiovascular disease (CVD) - coronary heart disease, angina, heart attack and stroke - or if they died.
This was an observational study, so no firm conclusions can be drawn about cause and effect, but the authors concluded that in participants older than 74 years without type 2 diabetes, statin treatment was not associated with a reduction in CVD or death.
But if people had diabetes, statin use was significantly associated with reductions in the incidence of CVD and death, they found.
"These results do not support the widespread use of statins in old and very old populations, but they do support treatment in those with diabetes who are younger than 85 years," they wrote.
But commenting on the study, Tim Chico, professor of cardiovascular medicine at the University of Sheffield, said: "Due to it's design this study cannot tell us whether or not statins reduce death or cardiovascular disease in older people.
"This study doesn't help me decide whether or not an elderly person should go on a statin, which as always should be a joint decision between patient and doctor based on a clear and open discussion about what benefits and risks are involved and include discussion about the other ways risk of cardiovascular disease can be reduced, such as physical activity and diet."
Professor Colin Baigent, director of the Medical Research Council Population Health Research Unit at the University of Oxford, added: "This problem with this type of study, which used routine health records, is that is a very unreliable way to determine the effects of statins on the risk of heart attacks and strokes.
"The only suitable method is a clinical trial where people are allocated to a statin or to no statin entirely at random."
In 2014, health officials at the National Institute for Health and Care Excellence advised that more patients should be taking statins to prevent heart attacks and strokes.
The health body suggested that as many as two in every five adults in England could be offered statins on the NHS.
Before the new guidance was issued in 2014, the drugs were offered to people in the UK who have a 20% risk of developing cardiovascular disease within 10 years.
But the health body reduced the threshold, calling on the NHS to widen this to cover people with just a 10% risk.
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