Smoking "rots" the brain, according to a new study by researchers at King's College in London.
The new study, published in the Age and Ageing journal, was conducted with 8,800 people over 50 years of age, and showed that smoking affected the brain, and in especially the memory of the study participants. Other side-effects, which are already well documents, included raised blood pressure and increased weight.
The researchers have said that the study showed how people needed to be aware that their lifestyles could affect their brains as well as their bodies.
The study was conducted to investigate connections between the raised likelihood of heart attacks and strokes in smokers, with the state of their brains.
Brain tests were performed on participants, asking them to learn new works, or name as many items in a category as possible in under a minute. Those surveyed were tested at the outset, as well as four years later and eight years later.
Researchers found that the overall risk of a stroke or heart attack was "significantly associated with cognitive decline" with those at the highest risk showing the greatest decline, according to the BBC.
There was also found to be data consistently linking smokers to those scoring lower in the tests.
Researcher Dr Alex Dregan has said: "Cognitive decline becomes more common with ageing and for an increasing number of people interferes with daily functioning and well-being. We have identified a number of risk factors which could be associated with accelerated cognitive decline, all of which, could be modifiable. We need to make people aware of the need to do some lifestyle changes because of the risk of cognitive decline."
The results did not cover further long term information, such as whether the drop in brain function could lead to increased chances of dementia, or act as any kind of hinderance in smokers' daily lives.
Dr Simon Ridley, from Alzheimer's Research UK, said: "Research has repeatedly linked smoking and high blood pressure to a greater risk of cognitive decline and dementia, and this study adds further weight to that evidence. Cognitive decline as we age can develop into dementia, and unravelling the factors that are linked to this decline could be crucial for finding ways to prevent the condition. These results underline the importance of looking after your cardiovascular health from mid-life."
The Alzheimer's Society has also said: "We all know smoking, a high blood pressure, high cholesterol levels and a high BMI [Body Mass Index] is bad for our heart. This research adds to the huge amount of evidence that also suggests they can be bad for our head too. One in three people over 65 will develop dementia but there are things people can do to reduce their risk. Eating a balanced diet, maintaining a healthy weight, exercising regularly, getting your blood pressure and cholesterol checked and not smoking can all make a difference," according to BBC.