Reducing working hours for care workers reduces their sick leave, makes them feel healthier and improves the care they give to their patients – but comes with an appropriate price tag.

These are the preliminary findings of a two-year experiment with a six-hour working day in Gothenburg, Sweden, which came to an end this month.

In February 2015, nurses at the Svartedalens retirement home switched from an eight-hour to a six-hour working day for the same wage – the first controlled trial of shorter hours in Sweden in about a decade.

Efficiency up, turnover down: Sweden experiments with six-hour working day Read more

To ensure that patients at the home for the elderly were attended to for the same number of hours as before, 15 new employees were hired for the duration of the experiment, costing the centre about an additional €600,000 (£510,000) a year – a 22% increase in gross cost.

But preliminary results found the benefits of the trial were considerable. Reduced working hours led to a 10% drop in sick leave, meaning the employer had to spend less to hire cover. Compared with care home workers with normal working hours, the perceived health of the carers at Svartedalens improved by about 50%.

The employees started to spend more of their reduced working hours on what the analysts classified as “social activity” with patients, such as games or outdoor walks, which can be particularly valuable for patients with dementia.

At the time, Lise-Lotte Pettersson, a 41-year-old assistant nurse at Svartedalens, said: “I used to be exhausted all the time. I would come home from work and pass out on the sofa. But not now. I am much more alert; I have much more energy for my work, and also for family life.”

Daniel Bernmar, the leader of the Left party group on Gothenburg city council, which pushed for the trial at Svartedalens, denied reports that the experiment had ended in failure.

“It still remains to be seen whether the economic costs of reduced working hours outweigh the benefits. The costs of the trial for the public economy were actually half of what we thought they would be,” he told the Guardian. A final set of results is expected in March.

Bernmar said the project had always been scheduled to end in 2017, and there had never been a plan to make the arrangement permanent at the end of the trial. During the experiment, the city council decided to set aside 20m Swedish krona (£1.8m) for similar reduced working hour trials in other sectors of Gothenburg’s public sector.

While historical data shows that the length of average working days has fallen in Sweden over the past century, there are no plans to establish six-hour working days at a national level.

The ideal length of a working day has also been the subject of debate in France, where the rightwing presidential candidate François Fillon has proposed a return to a legal working week of 39 hours in the public and private sectors, up from the 35-hour week that since 2000 has obliged employers to pay higher rates or give time off for extra hours.

Fillon said the 39-hour week would apply straight away in the public sector and that negotiated deals in the private sector can allow people to work up to an EU ceiling of 48 hours. He has suggested state workers be shifted to 39 hours, but paid for 37.