Condition category
Injury, Occupational Diseases, Poisoning
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Exposure to sunlight can have both positive and negative health impacts. Excessive exposure to ultra-violet (UV) radiation from the sun can cause skin cancer, however insufficient exposure to sunlight has a detrimental effect on production of Vitamin D. In the construction industry there are onsite proactive behaviours for safety, but sun-safety remains a low priority. There is limited research on understanding the barriers to adopting sun-safe behaviours and the association this may have with Vitamin D production. One approach is using text messaging in combination with a supportive smartphone App. The intervention aims to both reduce UV exposure during months with higher UV levels (April-September) and promote appropriate dietary changes to boost Vitamin D levels during months with low UV levels (October-March).

Who can participate?
Adults aged 18 to 65 years old working within the construction industry.

What does the study involve?
Participants are construction workers recruited across 9 constructions sites in the UK. Workers took part in 3 rounds of data collection (winter-summer-winter), with each round lasting 21 days. Half of the group, at each location, are randomly allocated to the one of two groups. Those in the first group receive a daily text message and smartphone App that gave people more information about sun safety at work and ways of boosting Vitamin D. The other half of the groups do not receive text messages or the App support. In the second and third rounds they switched to the opposite condition. The text messages reflected the time of year, e.g. in summer they were aimed at sun safety and in winter they received messages about increasing Vitamin D and healthier food choices. In the winter participants are given Vitamin D tablets to help increase levels when there is not enough sunlight for the body to make Vitamin D. At the start and end of each 21 day study all participants meet with the researcher to complete a Vitamin D test and questionnaires about their attitudes and beliefs. This allows the researchers to understand any changes in Vitamin D level and beliefs between people that received the text messages and people that didn’t. By visiting people at 3 times across the year also let the researchers look at the effect the seasons have on Vitamin D levels and beliefs.

What are the possible benefits and risks of participating?
Taking part in the study was not necessarily targeted to benefit people. However, we found that many of the people that took part had very low Vitamin D stores, specifically in the winter. This gave participants an insight into their own health with many self-reporting an uptake in boosting their Vitamin levels in the winter. People that took part were also given a £10 shopping voucher each time they provided a Vitamin D sample, so for each 21 day study they got £20 in vouchers. During the study we also spoke at industry events to increase awareness of sun safety at work and the importance of Vitamin D for general health. Finally, the study also provides important information about the effectiveness and feasibility of a technology-based intervention to promote sun-safety and healthy behaviours in outdoor construction workers that could be used in other occupational settings. There are no expected risks with participating.

Where is the study run from?
1. Heriot-Watt University (UK)
2. Institue of Occupational Medicine (UK)

When is the study starting and how long is it expected to run for?
January 2016 to May 2018

Who is funding the study?
Institute of Occupantional Safety and Health (UK)

Who is the main contact?
Professor John Cherrie (Scientific)

Trial website

Contact information



Primary contact

Prof John Cherrie


Contact details

Heriot-Watt University
EH14 4AS
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Nudging construction workers towards safer behaviour


Study hypothesis

Short punchy appropriate messages or "rewards" sent to the smartphone of workers will, along with other supporting organisational measures, promote healthy behaviour.

Ethics approval

Heriot-Watt University School of Life Sciences Ethics Committee, 28/06/2016, ref: 2016-164

Study design

Randomised controlled crossover trial

Primary study design


Secondary study design

Randomised cross over trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Change in Vitamin D level


Approximately 62 construction workers are recruited across 9 constructions sites in the UK (5 in Scotland and 4 in London). A randomised control crossover trial (RCCT) is used to test the intervention, with randomisation at site level – i.e. participants receive both the control (no text messages or supportive App support) and intervention (daily text messages and supportive App). Half of the group, at each location, were randomly allocated to the intervention. Workers take part in 3 rounds of data collection (winter-summer-winter), with each round lasting 21 days.

Using the Theory of Planned Behaviour (TPB) the intervention focuses on supporting sun-safety and healthy dietary decisions in relation to Vitamin D intake. The intervention emphasises cultivating the perception of normative support in the workplace, increasing awareness of control and self-efficacy in taking sun-protective behaviours, making healthier eating choices to boost Vitamin D, and tackling stigmas attached to image and group norms. Participants are invited to take part in three waves of data collection:
Visit 1: Low UV period (between October-March)
Visit 2: High UV period (April-September)
Visit 3: Low UV period (between October-March

Each study epoch lasts 21 days with intervention text messages delivered on workdays only. The supportive App provides supplementary information about sun protective behaviours and healthy dietary choices. The primary outcome measure is 25-hydroxy-Vitamin D [25(OH)D] level (obtained using blood spot sampling), which are taken pre and post control and intervention periods.

Secondary outcome measures are two-fold, using the TPB to detect changes in behaviour, and quantifying UV exposure during the UK peak radiation season (April-September) using body-mounted UV sensors.

Intervention type



Drug names

Primary outcome measure

Vitamin D levels are measured using blood spot sampling at the start and end of each 21 day epoch. The extent and direction of the change will be compared between groups in each of the high UV and low UV seasons using standard statistical methods, including comparison of mean levels of 25(OH)D change, comparison of proportion in each group whose levels increase or decrease; and within individual comparisons for intervention and control periods, which will control for differences between individuals in response to UV exposure. Secondary analyses will include additional comparisons of the level and direction of change in high and low UV periods in relation to geographic area of study (Scotland or England), different types of targeted intervention, and directly to the responses to the behavioural (i.e. TPB) and risk knowledge questionnaires

Secondary outcome measures

Behavioural change is measured using the Theory of Planned Behaviour at the start and end of each 21 day epoch. During the summer periods, we additionally measured personal exposure to UV radiation.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Health adults working in the construction industry and outdoors for long periods of time during the day.
2. Must have use of a smartphone to receive text messages and download an App.
3. Range of ethnic backgrounds
4. Range of ages
5. Range of professions within the industry (manual laborers and desk based office workers)
6. 18 to 62 years old

Participant type

Healthy volunteer

Age group




Target number of participants


Total final enrolment


Participant exclusion criteria

There is no participant exclusion criteria.

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Heriot-Watt University
EH14 4AS
United Kingdom

Trial participating centre

Institue of Occupational Medicine
EH14 4AP
United Kingdom

Sponsor information


Institute of Occupational Safety and Health

Sponsor details

The Grange
Highfield Drive
LE18 1NN
United Kingdom

Sponsor type




Funder type

Research organisation

Funder name

Institue of Occupantional Safety and Health

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

The results will be published in a final report to our funder and high impact, peer reviewed occupational health journals and an abridged report to our participating construction companies. We have intent to publish during 2018. The findings will also be disseminated to the wider public via annual conferences (e.g. Occupational Health 2018), to other organization members of our industry funder and through a series of engagement opportunities, which will be offered to participating construction companies. We do not have additional information at this time. This registration is intended to progress the submission of our protocol paper under review.

IPD sharing statement:
The current data sharing plans for the current study are unknown and will be made available at a later date.

Intention to publish date


Participant level data

To be made available at a later date

Basic results (scientific)

Publication list

2018 protocol in (added 23/10/2020)
2020 results in (added 23/10/2020)
2020 conference abstract in (added 23/10/2020)

Publication citations

Additional files

Editorial Notes

23/10/2020: The following changes were made to the trial record: 1. Publication reference added. 2. The total final enrolment was added.