If you needed another reminder of just how important quality sleep is to our health and well-being, a new study has linked three specific sleep problems with a change in risk of developing dementia.

Use of sleep medication and inability to fall asleep quickly (sleep-initiation insomnia) are associated with an increased risk of developing dementia over a 10 year period, the researchers found, while having trouble falling back to sleep after waiting (sleep-maintenance insomnia) comes with a reduced dementia risk.

The findings are notable, as this is the first study to examine the relationship between dementia risk and long-term sleep disturbance in a nationally representative sample of older adults in the US. Its conclusions are worth paying attention to, matching those of studies using smaller samples.

"After reading the existing literature, I was surprised to see mixed findings on the sleep-dementia relationship, so I decided to investigate this topic," says Roger Wong, a public health scientist at the State University of New York Upstate Medical University.

"We expected sleep-initiation insomnia and sleep medication usage to increase dementia risk, but we were surprised to find sleep-maintenance insomnia decreased dementia risk."

The researchers looked at a decade of data from a longitudinal panel study called the National Health and Aging Trends Study (NHATS), specifically at 6,284 adults over the age of 65 who lived in the community, and hadn't been diagnosed with dementia at the start of the study period.

The unadjusted measurements of sleep-initiation insomnia showed the most dramatic link: those who reported it had a 51 percent higher risk of dementia. The researchers note this increase was reduced when sociodemographic and health factors were taken into consideration, however, to the point it was no longer statistically significant.

For sleep medication, the statistics showed a 30 percent increased dementia risk (after sociodemographic but before health adjustments).

It is important to note these results do not indicate that sleep disturbances are a defining factor leading to dementia – rather they show an association, and a need to further investigate other factors that modify the association.

On the other hand, there was a 40 percent decreased dementia risk (after both sociodemographic and health variables had been factored in) for sleep-maintenance insomnia.

It's that last figure that surprised researchers the most. The team suggests that more time awake might keep cognitive functions ticking over, without necessarily having a detrimental impact on the quality of the sleep that is banked through the night – a suggestion reflected in previous studies

"By focussing on the variations in sleep disturbances, our findings can help to inform lifestyle changes that can reduce dementia risk," says Margaret Anne Lovier, a Research Fellow at the State University of New York Upstate Medical University.

On its own, this study isn't enough to prove cause and effect – that the sleep problems are causing the dementia – but it does highlight a relationship between the two that both researchers and doctors need to know about. It's also worth noting that sleep disturbances are common for both people who have dementia and for older people.

The findings could be used to better assess dementia risk for older adults. The researchers also called for further study into the relationship between sleep disturbance and specific dementia types, which this investigation didn't explore.

"Older adults are losing sleep over a wide variety of concerns," says Wong. "More research is needed to better understand its causes and manifestations and limit the long-term consequences."

The research has been published in the American Journal of Preventive Medicine.