A new study has found that symptoms of depression that steadily increase over time in older age could indicate early signs of dementia.

According to Dutch scientists, other patterns of symptoms, such as chronic depression, appear not to be linked.

Researchers looked at different ways depression in older adults progressed over time and how this related to any risk.

They concluded worsening depression may signal dementia is taking hold.

The research, published in The Lancet Psychiatry, followed more than 3,000 adults aged 55 and over living in the Netherlands.

All had depression but no symptoms of dementia at the start of the study.

Dr. M. Arfan Ikram of the Erasmus University Medical Center in Rotterdam said depressive symptoms that gradually increase over time appear to be a better predictor of dementia later in life than other paths of depression.

“There are a number of potential explanations, including that depression and dementia may both be symptoms of a common underlying cause, or that increasing depressive symptoms are on the starting end of a dementia continuum in older adults,” he said.

Only the group whose symptoms of depression increased over time were found to be at increased risk of dementia – about one in five of people (55 out of 255) in this group developed dementia.

Others who had symptoms that waxed and waned or stayed the same were not at increased risk.

For example, in those who experienced low but stable levels of depression, around 10% went on to develop dementia.

However, the exact nature of depression on dementia risk remains unknown.

They often occur together, but the Dutch study is among the first to look at different patterns of depression symptoms.