Article Link: The Lancet Respiratory Medicine, August 2024
In the largest study of its kind, UK researchers found that using nasal sprays at the first sign of a cold reduced illness duration by about 20% (roughly 2 days) and cut antibiotic use by one-quarter to one-third—and surprisingly, plain saline spray worked just as well as the fancier gel-based version. A website promoting physical activity and stress management had a modest effect on preventing colds (5% reduction in getting sick) and also reduced antibiotic use. These simple, scalable interventions could meaningfully reduce the burden of respiratory infections across entire populations if widely adopted.
Lead Researchers:
Study Scope:
Funding and Conflicts:
The Setup: Nearly 14,000 adults at higher risk for respiratory complications (age 65+, chronic conditions, or frequent colds) were randomly assigned to one of four groups for six months during winter cold seasons (2020-2023):
Participants reported their illness days, symptoms, antibiotic use, and work days lost monthly for six months.
The Numbers:
Massive Scale and Real-World Design Nearly 14,000 participants make this by far the largest study of nasal sprays or behavioral interventions for colds. The pragmatic design—people using these at home without intensive support—means results likely translate to everyday use.
High-Quality Methodology Pre-registered protocol, multiple sites, stratified randomization, and 79-86% follow-up rates are all markers of rigorous research. The statistical analysis plan was finalized before looking at results, preventing data dredging.
Accessible, Scalable Interventions Unlike previous studies requiring supervised exercise classes or intensive mindfulness programs, these interventions need no professional support. Both nasal sprays are available over-the-counter; the website requires zero ongoing costs.
Multiple Meaningful Outcomes The study didn't just look at symptom days—it captured antibiotic use (critical for antimicrobial resistance), work productivity, and healthcare contacts. All showed benefits, suggesting real-world impact.
Person-Based Development Researchers iteratively developed the interventions with patient input, increasing the likelihood that people would actually use them. This is smart translational research.
Important Comparison Finding Demonstrating that plain saline works as well as the marketed gel-based spray is valuable consumer information and suggests the mechanism is mechanical washing rather than antiviral chemistry.
Open-Label Design (No Blinding) Participants knew which intervention they received, which could introduce placebo effects or reporting bias. However, the researchers make a reasonable argument that placebo effects are minimal for respiratory infections based on prior studies comparing open-label to blinded trials.
Self-Reported Outcomes Only No viral confirmation of infections, no objective measures—just what people remembered and reported. While this matches how people experience illness, it's subject to recall bias and couldn't distinguish viral from bacterial infections.
Modified Intention-to-Treat Analysis Due to statistical convergence problems, they analyzed only people with complete data (complete case analysis) rather than using imputation for missing data as originally planned. This can introduce bias if people who dropped out differed systematically from completers.
Modest Adherence Only about 58-60% used nasal sprays at first sign of illness as directed, and just 25-27% used them preventatively after exposure to sick people. Real-world effectiveness might be even better (or worse) depending on how people actually use these products.
Missing Key Subgroup Data The study couldn't definitively answer whether the interventions work better for certain groups. Post-hoc analyses suggested the behavioral website worked better for people with multiple risk factors and possibly worse for smokers, but these weren't pre-specified analyses.
Limited Diversity Only 3% of participants were from ethnic minority groups (vs. 6% in the UK population for this age group), and the study excluded people without internet access. Results may not generalize to more diverse or disadvantaged populations.
Can't Determine Mechanism Because saline worked as well as the pH-buffered spray, we don't know if the mechanism is mechanical washing (as saline suggests) or viral inactivation from pH buffering (as originally hypothesized). This matters for understanding how and when to use these interventions.
Pandemic Context The study spanned COVID-19 waves (2020-2023), which likely altered normal respiratory infection patterns, masking behaviors, and healthcare seeking. The authors note effects were larger in the third season (more "normal"), suggesting pandemic years may have diluted the true effect.
This well-designed study suggests that simple interventions we can all do—squirting salt water up your nose when you feel a cold coming on, or using a website to stay active and manage stress—might meaningfully reduce how long colds last and how much we reach for antibiotics. The absolute benefit for any one person is modest (a day or two less illness), but if millions of people did this, it could reduce antibiotic resistance and lost work days substantially. The surprising finding that cheap saline spray works just as well as the marketed antiviral spray is both scientifically interesting (suggests the mechanism is mechanical rather than chemical) and practical (you don't need to buy the expensive stuff).
The practical takeaway: Keep a saline nasal spray handy and use it liberally when you feel a cold starting—it's safe, cheap, and this study suggests it actually works.