Researchers at the Children’s Hospital of Philadelphia (CHOP) have discovered that circadian rhythms, the body's internal biological clocks, can significantly affect recovery outcomes from influenza infections. Their findings, published in the Journal of Clinical Investigation, suggest how understanding these rhythms can enhance care for critically ill patients suffering from respiratory viral infections.
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Circadian rhythms are biological processes that cycle roughly every 24 hours, enabling organisms to adjust to environmental changes. Individual organs and cells operate on their own circadian schedules, which can be disrupted by factors such as shift work or jet lag, leading to decreased alertness, disturbed sleep patterns, and negative health effects. Less known is that the host's circadian state can also directly influence infection outcomes.
Light and mealtime serve as critical external cues, or “zeitgebers,” that align with various biological processes in organs and cells. Previous studies indicated that certain times of day offer better protection against viruses like influenza, but the role of external cues in enhancing the body's internal timing mechanisms was unclear.
Senior study author Shaon Sengupta, MBBS, MPH, an attending neonatologist at CHOP, noted that because influenza affects patients over several days, they could examine how external cues like light maintain time-of-day-specific protection throughout the duration of the infection. The research found that disrupting environmental light cues during critical vulnerability periods diminished the protective effects previously observed, leading to an imbalanced immune response, particularly with inflammatory cells accumulating in the lungs during respiratory infections.
However, keeping a consistent meal schedule appeared to counteract the negative effects of disrupted light cycles, indicating that external cues can help stabilize the body's clocks.
Sengupta emphasized that these findings are especially pertinent for hospitalized patients, who often experience circadian disruptions due to irregular light and meal timings. The study underscores that a host’s circadian health is crucial for determining clinical outcomes and points towards incorporating circadian-sensitive practices in hospital settings. Such practices may include adjusting light exposure and meal timings to enhance immune responses and facilitate quicker recovery.
This research was supported by the National Institutes of Health and the Raine Medical Research Foundation. The original study can be referenced as Paul et al, “Effect of external cues on clock-driven protection from influenza A infection,” Journal of Clinical Investigation, online November 17, 2025, DOI: 10.1172/JCI193133.