Alzheimer's disease is associated with a reduced risk of cancer and vice¹ versa, a study suggests.

调查显示，患老年痴呆症的人患癌症的风险很小，反之亦然。

The number of dementia patients in the UK is predicted to double

US researchers followed 3,020 people aged² 65 and above for the study, published in the journal Neurology神经学.

Those who had Alzheimer's at the start of the study were 69% less likely to be admitted to hospital with cancer than those free of the disease at the start.

And those with cancer at the study's start were 43% less likely to develop Alzheimer's than the cancer free.

The researchers followed the subjects for an average of five years to see whether they developed Alzheimer's, and an average of eight years to see whether they developed cancer.

At the start of the study, 164 people (5.4%) already had Alzheimer's disease and 522 people (17.3%) already had a cancer diagnosis³.

During the study, 478 people developed dementia痴呆 and 376 people developed invasive cancer.

The researchers stressed that more work was needed before any firm conclusions could be drawn⁴, and said the findings only seemed fully⁵ to apply to white people.

They found no association between cancer and another type of dementia, known as vascular⁶ dementia血管性痴呆, which is thought to be caused by a lack of blood supply to the brain.

However, patients with this condition died earlier than people with Alzheimer's.

Lead researcher Dr Catherine Roe⁷, of Washington University School of Medicine in St Louis, said this suggested the association between Alzheimer's and cancer was not simply due to people with those conditions dying before they could contract the other ailment小病，不安.

"Discovering the links between these two conditions may help us better understand both diseases and open up avenues大道，方法 for possible treatments," she said.

"Alzheimer's disease and cancer are both characterised by abnormal, but opposing, cellular⁸ behaviour.

"In Alzheimer's disease, excessive cell death occurs, whereas cancer is characterised by excessive cell growth.

"Other scientists have suggested that there are certain molecular⁹ pathways that may influence both Alzheimer's disease and cancer."

For instance, one specific enzyme酶 has been shown to target a number of proteins, some of which are believed to stimulate¹¹ cancer, some to suppress it, and others to be a hallmark品质证明，特点 of Alzheimer's.

Rebecca Wood, chief executive of the Alzheimer's Research Trust, agreed the study raised hopes of finding new ways to prevent or treat disease.

She said: "This study suggests that there might be a link between cancer and Alzheimer's, but it is much too soon to say for certain whether the two diseases are connected.