Counting pollen instead of sheep? Investigating the relationship between pollen exposure and sleep

Airborne pollen is a well-known trigger of allergic symptoms, but its impact on sleep quality remains unclear.

Sleep was assessed in 373 adults over two weeks using Fitbit Inspire 2 wristbands. Sleep metrics included total sleep duration, time awake after sleep onset, and time in light, rapid eye movement (REM), and deep sleep. Individually-relevant pollen exposure (IPE) was calculated by summing those hourly concentrations out of seven allergenic pollen types (alder, ash, birch, hazel, grasses, mugwort, ragweed) to which participants were sensitized according to skin prick tests. Associations between IPE and sleep were examined using generalized additive mixed models with personal random intercepts. Subgroup analyses explored effect modification, and a secondary analysis evaluated associations between a nasal symptom score and sleep outcomes. Sensitivity analyses tested alternative pollen exposure windows.

No significant associations were found between IPE calculated over the 18 hours preceding sleep end and any of the five sleep outcomes. An IPE increment of 200 pollen grains/m³ was associated with increased light sleep in the overweight/obese subgroup (+7.4 min; 95% Confidence Interval (CI): +0.1 to +14.8 min), and in the subgroup that took allergy medication before the sleep episode (+4.3 min; 95% CI: +0.4 to +8.2 min), but the number of significant findings was consistent with chance at a 5% significance level among 80 associations tested. The nasal symptom score was not associated with sleep outcomes. Longer exposure windows did not show significant associations with sleep outcomes either.

We found no associations between IPE and sleep outcomes, regardless of exposure window duration.