Unpacking the studies of Prof. Dr Tøve Fjeld

This week we’re unpacking the studies of Professor Dr. Tøve Fjeld. Fjeld is a Norwegian botanist born in 1958 who researched the effects of plants on humans.

In the 1990s, she carried out a major study into the connection between plants and people's well-being. The study was titled: “The Effect of Interior Planting on Health and Discomfort among Workers and School Children”

The objective of her three studies was to assess whether indoor plants used for decoration or a combination of plants and full spectrum daylight fluorescent light affected self-reported human health and discomfort symptoms.

Now I’ll run through the three studies.

The first was on office workers and just involved plants. In this study, 51 office workers alternated between periods with plants in their offices and periods without, three months in Spring ‘95 and three months in Spring ‘96. They had to answer a questionnaire every second week, rating 12 different health symptoms with a 0 to 3 rating.

In this study, it was found that the average score, as an average of 12 symptoms, was 23% lower when the participants were exposed to plants in their offices compared to the period without plants, so a 23% reduction in symptoms of ill health.

In particular, complaints regarding coughs were reduced by 37% and fatigue reduced by 30%. The self-reported level of dry or hoarse throat and dry or flushed facial skin each decreased about 23% with the plants.

So, if the symptoms are grouped by the body’s responses, a significant reduction was obtained in neuropsychological symptoms (fatigue, feeling heavy-headed, headache, dizziness, and concentration problems) and in mucous membrane symptoms (itching or irritation of the eyes; irritated, running, or stuffy nose; dry or hoarse throat; and cough), while skin symptoms seemed to be unaffected by the plants.

On top of this, 82% of participants reported feeling more comfortable with plants in their office, and they expressed a strong desire to keep them in the future.

The second study took place with 48 staff members who worked in shifts in a windowless hospital radiology room.

To establish baseline health levels, the staff had to complete a 12 question questionnaire four times in two months. Following that, 23 planters were installed in the space, along with full spectrum lighting.

The health questionnaire was then filled in over the next four months, along with demographic data, working hours data, and 51 air samples.

The results showed a 25% overall reduction in health complaints. Fatigue was reduced by 32%, headaches by 45%, and dry throat by 31%. Interestingly, staff who spent the most time in the room experienced the greatest improvements, showing the cumulative benefits of being surrounded by plants.

The third and final study was on Junior High School Pupils in classrooms.

The background to this study was significant problems with the indoor air quality in the classrooms at a junior high school near Oslo in Norway. As part of the study, three classrooms were planted with tropical, indoor plants and a full spectrum lighting system was installed.

A pilot survey was conducted among pupils and teachers, through four different questionnaires. The questionnaires collected information on wellbeing, health, and discomfort symptoms, as well as information about how the pupils perceived their indoor environment. A control group of students in other classrooms were also set up.

When the results were analysed, health issues were 21% lower among pupils in planted classrooms compared to those in the control classrooms. Complaints regarding headaches and dry or hoarse throats were found to be 37% and 36% lower, respectively, among pupils in planted classrooms compared to the control. No significant differences between pupils in the two types of classrooms were observed regarding symptoms of flu or colds: both groups of pupils seemed to be affected at the same range. In spite of this, complaints regarding respiratory symptoms (dry, itching eyes and dry or hoarse throat) and headache were significantly lower in the planted classrooms, indicating less strain induced by the indoor environment.. Additionally, pupils rated their classrooms as more comfortable and pleasant. These findings highlight the significant benefits of greenery in educational settings, both for health and the overall learning environment.

So, lets sum it up with a conclusion!

The three studies were conducted at different locations, at different times, and with different subjects, yet the results were in the same range when it came to the level of reduction of health and discomfort symptoms due to the interventions In addition, a quite similar trend was found regarding which specific symptoms or symptom groups were affected: neuropsychological symptoms, such as fatigue and headache, and mucous membrane irritations and irritations of respiratory organs seemed to be affected more than skin symptoms.

In the office study and the radiology department study, analyses were conducted regarding demographics. No significant differences in any of the two studies were found regarding age, gender or smoking habits among the subjects.

Fjeld concluded that her findings could have several main explanations:

1. An improvement of air quality by the plants

2. An increase in general well-being due to the perception of plants

3. An appreciable influence from establishing a more nature-like indoor light environment

4. An effect of increased attention towards the employees.

We’ll cover these points off one-by-one.

When the subject of plants purifying air is raised, it is often remarked that in an office environment an adequate ventilation system would remove pollutants much faster than plants and that the air changes would render the plants’ contribution insignificant. Fjeld observes this but remarks that a minor change in the content of air contaminants might, have a positive influence on the employees’ experience of comfort, and thereby result in a lower score on the self-reported health and discomfort symptoms. The symptoms chosen for this study are known to be affected by indoor air quality.

Alongside this, it was noted that the plants were all relatively close to the participants, so a local improvement in air quality could have had an impact on the participants, this could particularly be the case with increased humidity in the immediate vicinity of the plants.

As for the perception of the plants leading to the health improvements, Fjeld closely links this with Ulrich’s 1984 study which I’ve covered extensively - I’ll link the video here!

The lights were considered as a reason for the improvement in the health of the participants and it was concluded that studies on seasonal affective disorder (give reason to believe that both the light level and the spectral constitution of light might influence health and well-being—especially symptoms regarding neuropsychological effects

Finally, the effect of increased attention towards the employees could be a factor, however, attempts were made during the study to exclude this as much as possible, and the positive benefits persisted long after initial engagement with the participants, so it wasn’t considered significant.

Ultimately, the findings of this study are that plants do have a statistically significant effect on people’s physical health in indoor environments, whether in offices, schools, or healthcare facilities.

I hope you found this unpacking of Dr Fjeld’s studies interesting, if you did, make sure to subscribe to our YouTube channel for more on how plants can enhance our spaces and wellbeing.