"It's a snapshot. The prevalence of malnutrition risk isn't well established in New Zealand."
Wham said no clear cause could be identified, with a number of factors at play.
"There's a whole raft of reasons. As people age a lot of physiological elements conspire against them. They absorb nutrients less well and total energy needs are less, so they often don't eat enough food and that's a problem.
"One of the key issues is people who live and eat alone. Eating is socially facilitated, in other words, companionship facilitates eating.
"For people that live alone you can imagine that they don't have the motivations to cook and eat meals."
Reduced food intake can contribute to dysphagia - a condition which causes swallowing difficulties. Wham said this can initiate "a vicious cycle further decreasing food intake and further exacerbating poor swallowing function."
On top of the individual impact, Wham also said the situation also places strain on the healthcare system.
"It's associated with higher infection rates, loss of muscle mass, strength and function, longer length of hospital stays, as well as increasing morbidity and mortality," she said.
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