Assessing the efficacy of behaviourally informed invitation messaging in increasing attendance at the NHS Targeted Lung Health Check: A randomised experimental study

This randomized experimental study found that behaviorally informed invitation messages failed to significantly increase intention to attend NHS Targeted Lung Health Checks compared to a control message, highlighting the need for future interventions to directly address emotional barriers like fear and better align message content with empirically identified behavioral influences.

The Gist

Imagine the NHS (the UK's national health service) is trying to get people to go to a "Lung Health Check." Think of this check-up like a fire drill for your lungs. It's a quick scan that can catch lung cancer early, when it's easy to fix, rather than waiting until it's a raging inferno that's hard to control.

The problem? Not enough people are showing up for the drill. Even though it's free and could save lives, many eligible smokers and ex-smokers are ignoring the invitation letter in their mailbox.

So, the NHS decided to try a new strategy: changing the words on the invitation letter. They wanted to see if using "psychological tricks" (behavioral science) could get more people to say, "Yes, I'll go."

Here is the story of their experiment, broken down simply.

The Experiment: Five Different Letters

The researchers created five different versions of the invitation letter and sent them to over 3,000 people (aged 55–74 who smoke or used to smoke). They asked these people: "How likely are you to go to this check-up after reading this letter?"

The letters were:

1. The Standard Letter (Control): Just the facts. "We offer this for free. Here is how to book."
2. The "Happy Ending" Letter (Gain-Frame): Focused on the good stuff. "If you catch it early, treatment works great, and you can keep doing the things you love!"
3. The "Doctor's Note" Letter (Messenger): Said, "Your own GP (family doctor) recommends you do this."
4. The "Don't Wait" Letter (Status Quo): Focused on urgency. "It's your turn now. Don't delay, book it today."
5. The "Don't Be Selfish" Letter (Challenging Assumptions): Told people, "If you wait until you're sick, it costs the NHS more money. Don't be a burden; come now."

The Big Surprise: The Letters Didn't Work Much

The researchers expected that the "psychological" letters would be like magic spells, making people suddenly want to go.

The reality? The magic spells didn't work.

• The "Happy Ending," "Don't Wait," and "Don't Be Selfish" letters were no better than the boring standard letter.
• The only one that showed a tiny spark of success was the "Doctor's Note" letter. People were slightly more likely to say they'd go if they thought their own GP wanted them to. But even this small boost wasn't strong enough to be considered a "win" after doing the math.

Why Didn't It Work? The "Missing Puzzle Pieces"

This is the most important part of the story. The researchers asked the participants: "What stops you from going?" and "What would make you go?"

They found the answers were like missing puzzle pieces in the letters:

• The Big Barrier: Fear. The number one thing stopping people was scared. They were terrified of finding out they had cancer, or even just terrified of the scan itself.
  • The Problem: None of the letters tried to comfort this fear. They didn't say, "It's okay to be scared, but here is how we will help you."
• The Second Barrier: Social Pressure. People felt judged because they were smokers. They thought, "My doctor will be disappointed," or "I feel ashamed."
  • The Problem: The letters didn't address this shame.
• The Big Motivator: Belief. The main reason people did want to go was the belief that "Early detection saves lives."
  • The Good News: The letters did talk about this, but it wasn't enough to overcome the fear.

The Metaphor: Imagine you are trying to get a child to eat their vegetables.

• The letters tried to say: "Vegetables make you strong!" (Gain-Frame) or "Your mom says eat them!" (Messenger).
• But the child is screaming, "I'm scared I'll get a tummy ache!" (Fear) and "Everyone is staring at me!" (Social Influence).
• Because the letters didn't address the fear or the shame, the child (the patient) didn't eat the vegetables (go to the check-up).

The "Fear" Twist

There was a funny twist with the "Doctor's Note" letter.

• It worked a little bit because people trust their doctors.
• BUT, reading that their GP recommended it also made people feel more scared. It made the threat feel more real.
• It was like a double-edged sword: The letter gave them a nudge to go, but it also made them tremble a bit more. Fortunately, the "trust" part was slightly stronger than the "fear" part, so they still said "yes" a tiny bit more often.

The Lesson for the Future

The study concludes that you can't just throw "psychological tricks" at a problem and hope it works.

If you want to get people to do something scary (like a medical check-up), you have to listen to their fears first.

• Don't just say: "This is good for you!"
• Do say: "We know this feels scary. It's normal to be nervous. But your doctor is here to help, and catching it early means you can keep living your life."

In short: The NHS tried to "nudge" people with clever letters, but they forgot to hold their hands. To get more people to the lung health check, the next letters need to be less about "smart tricks" and more about reassurance and empathy.

Technical Summary

1. Problem Statement

Lung cancer screening via Low-Dose Computed Tomography (LDCT) significantly reduces mortality through early detection. However, the uptake of the NHS Targeted Lung Health Check (TLHC) programme remains low (averaging 35%), with participation disproportionately lower among high-risk groups (current smokers and those from lower socio-economic backgrounds).

While behaviourally informed messaging (e.g., "nudge" techniques) has shown promise in other health contexts, evidence regarding its effectiveness in lung cancer screening is mixed. A critical gap exists in the literature: few intervention studies utilize evidence-based behaviour change frameworks to systematically link identified population-specific barriers and enablers to intervention content. Consequently, it is unclear whether existing invitation messages effectively address the psychological and social drivers of non-attendance.

2. Methodology

The study presents a secondary analysis of data from a large-scale, between-subjects randomised controlled trial (RCT) conducted by NHS England in October 2023.

• Participants: 3,274 adults aged 55–74 years with a history of smoking (current or former), recruited via market research panels and NHS apps.
• Design: Participants were randomly allocated to one of five conditions:
  1. Control: Standard invitation letter wording.
  2. Gain-Frame: Emphasized positive outcomes of early detection and treatment success.
  3. Messenger: Included a recommendation from the participant's General Practitioner (GP).
  4. Status Quo: Framed attendance as a timely, expected default action with prompts to act immediately.
  5. Challenging Assumptions: Countered misconceptions about burdening the NHS and highlighted the costs of delay.
• Measures:
  • Primary Outcome: Self-reported likelihood of attending a TLHC appointment (7-point Likert scale).
  • Secondary Outcomes: Selection of up to three barriers and three enablers from a predefined list, mapped to the Theoretical Domains Framework (TDF).
  • Mediators: Emotional responses (specifically fear and nervousness) selected from a predefined list.
• Analytical Approach:
  • Intervention Efficacy: Bootstrapped one-way ANOVA and Welch's t-tests with Bonferroni correction to compare intention across groups.
  • Barrier/Enabler Analysis: Qualitative coding of reported reasons using the TDF.
  • Alignment Analysis: Mapping the Behaviour Change Techniques (BCTs) within the messages (using the BCT Taxonomy v1) to the TDF domains identified by participants, utilizing the Theory and Techniques Tool (TaTT) to assess theoretical congruence.
  • Mediation Analysis: Counterfactual-based mediation analysis (interventional direct and indirect effects) to determine if fear/nervousness mediated the relationship between message type and attendance intention.

3. Key Contributions

• Systematic Framework Application: This study is the first to apply the Behaviour Change Wheel (BCW) and TDF to evaluate existing invitation messages in the context of lung cancer screening, moving beyond simple "nudge" frameworks to a rigorous theoretical alignment check.
• Diagnostic Evaluation: It demonstrates a method for diagnosing why behaviourally informed messages may fail by assessing the alignment (or misalignment) between intervention content and empirically identified population barriers.
• Policy Relevance: The findings provide direct evidence to inform the redesign of national screening invitation strategies, addressing a key priority for the UK's NHS Lung Cancer Screening programme.

4. Results

• Intervention Efficacy:
  • Behaviourally informed messages did not meaningfully increase intention to attend compared to the control message.
  • The Messenger condition (GP endorsement) showed a small, unadjusted advantage (0.19-point increase in intention) over Control, Gain-frame, and Status Quo conditions. However, this effect did not remain significant after adjustment for multiple comparisons (Bonferroni correction).
• Barriers and Enablers (TDF):
  • Top Barriers: Social Influence (37.5%, e.g., lack of GP recommendation, fear of judgment), Emotion (31.8%, e.g., fear of diagnosis), and Knowledge (25.8%, e.g., "no symptoms").
  • Top Enablers: Beliefs about Consequences (81.2%, e.g., early detection is treatable), Emotion (46.1%, e.g., reassurance), and Optimism (28.2%).
• Message Alignment:
  • The tested messages addressed only 57% of the reported barriers and enablers.
  • Crucially, the messages failed to address the two most prevalent barriers: Emotion (fear) and Social Influence. The messages primarily targeted Beliefs about Consequences and Knowledge.
• Mediation by Fear:
  • Fear was negatively associated with intention to attend (participants feeling scared were 0.66 points less likely to attend).
  • The Messenger condition paradoxically increased the odds of participants reporting fear compared to the control (OR = 1.65).
  • Despite increasing fear, the Messenger condition still showed a modest positive direct effect on intention, suggesting the benefit of GP endorsement operated through other pathways (e.g., credibility) that outweighed the negative impact of induced fear, though the fear effect was not statistically significant in the indirect path.

5. Significance and Implications

• Limitations of Generic Nudges: The study suggests that low-cost messaging interventions that do not directly address emotional and social barriers (specifically fear and lack of GP endorsement) have limited impact on lung cancer screening uptake.
• Need for Targeted Design: Future interventions must be designed using a systematic process (BCW) that explicitly maps Behaviour Change Techniques to the specific TDF domains identified as barriers in the target population.
• Emotional Management: The findings highlight that credible recommendations (like GP endorsements) can inadvertently trigger fear. Effective future messaging should decouple credibility from fear by explicitly acknowledging and normalizing emotional concerns (e.g., "It is normal to feel worried, but early checks are vital...").
• Policy Recommendation: To improve uptake, invitation strategies should move beyond informational or generic behavioural nudges and incorporate specific techniques to address emotional regulation (e.g., social support, reassurance) and social influence (e.g., explicit GP recommendations).

In conclusion, while the specific messages tested did not significantly outperform standard invitations, the study provides a robust methodological framework for diagnosing intervention failures and underscores the necessity of aligning message content with the deep-seated emotional and social barriers preventing screening attendance.