Why Your Afternoon Light Matters More Than You Think

Relationships between light exposure and aspects of cognitive function in everyday life

The paper asks a simple question with a messy real-world twist: in everyday life (not a lab), do differences in the light you experience relate to how alert you feel and how well you perform on basic cognitive tasks?

What the authors did

• Sample: 58 UK adults (convenience sample) tracked for ~7 days of normal life; subset of 41 also completed an optional in-lab light-sensitivity session.

• Light measurement: a wrist-worn device logged melanopic equivalent daylight illuminance (EDI) every 30 seconds (a proxy emphasizing the melanopsin/ipRGC pathway often implicated in alertness and circadian biology).

• Cognition in the wild: participants used a smartphone app repeatedly through the day to report subjective sleepiness and complete short tasks for vigilance (PVT), working memory (3-back), and visual search.

Main findings

1) Recent bright light is linked to feeling less sleepy and responding faster

After adjusting for time-of-day and sleep-related factors, higher light exposure in the preceding window (30–120 minutes) was associated with:

• Lower subjective sleepiness (strongest up to ~2 hours).

• Faster reaction times on vigilance and working memory tasks (most robust around a 30-minute window for vigilance; up to ~1.5 hours for working memory).

The effect sizes are modest but measurable:

• A 1 log-lux increase in melanopic EDI corresponded to about a 0.2-point reduction in sleepiness score (on their scale).

• From very dim to bright outdoor conditions (a 4 log-lux span), vigilance reaction time improved by about 30 ms, and working-memory reaction time by about 60 ms.

2) Habitual “bright, stable days” correlate with better overall performance

Across the week, people with:

• Brighter daytime exposure (their “M10”: average brightness during the brightest 10 hours), and

• Less fragmented daily light patterns (lower intradaily variability),

tended to show better performance on several endpoints, including fewer errors (e.g., fewer false positives in visual search and working memory) and faster vigilance reaction times; key associations remained after adjusting for covariates.

3) Earlier “dark phase” and brighter days strengthened the light–sleepiness link

Participants with earlier timing of their dimmest-light period (used as an inferred proxy for earlier bed/rest timing) and higher daytime light showed a stronger relationship between recent light and reduced sleepiness.

4) Lab “photosensitivity” tests did not cleanly predict real-world sensitivity

The authors tried to predict who is most “light sensitive” (cognitively) using in-lab melanopsin-related measures (pupil tests and psychophysics). Overall, these did not robustly predict the real-world light–cognition slopes.

How the authors interpret it

They argue the results support two overlapping ideas:

1. Acute bright light exposure is associated with arousal-like benefits (alertness and faster reactions).

2. Habitual patterns of brighter, more stable daytime light may support cognition indirectly, potentially by supporting circadian robustness and sleep homeostasis.

Limitations to keep in mind

• The sample largely excluded people with major circadian disruption (e.g., night shift work), so effects could differ in those populations.

• Small sample for probing individual differences (e.g., genetics/age effects on photosensitivity not explicitly controlled).

• Correlational, not an intervention study, so it cannot establish causality (bright light might improve performance, but lifestyle factors correlated with bright light could also be driving results).

Bidirectional associations between sleep and physical activity investigated using large-scale objective monitoring data

https://www.nature.com/articles/s43856-025-01226-6

What the researchers wanted to know

We hear two common health messages: “get enough sleep” and “be physically active.” But it is not obvious whether people can realistically do both, day after day—and whether sleep and activity truly influence each other in everyday life (not just in short experiments). (Nature)

What they did

The authors analyzed objective, long-term data from 70,963 adults using two consumer devices: an under-mattress sleep sensor and a wrist-worn activity tracker. The dataset covered January 2020 to September 2023, across 244 geographic regions, totaling about 28 million person-days/nights. (Nature)

They asked two main questions:

1. How many people routinely hit commonly cited thresholds for both sleep and activity?

2. On a day-to-day basis, does sleep predict next-day step count, and does step count predict next-night sleep (and are those relationships non-linear)? (Nature)

What they found

1) Very few people consistently achieve both targets

Using common benchmarks (roughly 7–9 hours of sleep and >8,000 steps/day), only 12.9% of participants routinely met both. At the other end, 16.5% combined short sleep (<7h) with a sedentary step profile (<5,000 steps/day). (Nature)

2) Sleep was a stronger predictor of next-day activity than the reverse

In the day-to-day modeling, sleep characteristics were meaningfully associated with next-day steps, while steps had little association with the following night’s sleep.

Key patterns:

• Sleep duration vs. next-day steps: In the unadjusted analyses, the curve peaked around ~6 hours, but when the authors accounted for time awake (a critical confounder—if you sleep less, you simply have more waking hours to accumulate steps), the peak shifted closer to ~7 hours and the differences got smaller. (Nature)

• Sleep efficiency (how much time in bed is actually spent asleep): Higher sleep efficiency predicted more next-day steps (e.g., ~25th to 75th percentile difference corresponded to ~+282 steps/day, smaller after adjusting for awake time). (Nature)

• Sleep onset latency (how long it takes to fall asleep): Taking longer to fall asleep predicted fewer next-day steps (again, somewhat smaller after adjusting for awake time). (Nature)

• Steps → next-night sleep: Associations existed in places, but were small and often largely disappeared after adjusting for wake time—leading the authors to argue that the practical impact of “more steps today = better sleep tonight” was limited in these data. (Nature)

How to interpret this (without over-reading it)

• The headline result is not “sleep 6 hours to be more active.” The paper’s own adjustment shows that much of the apparent “6-hour advantage” is explained by having more hours awake to accumulate steps; once you control for that, the peak moves toward ~7 hours and the effect size shrinks. (Nature)

• A more defensible takeaway is: sleep quality (especially efficient sleep and falling asleep more easily) is linked with being more active the next day, while simply piling on steps may not strongly shift your sleep that night (at least as captured by these devices and metrics). (Nature)

Important limitations to keep in mind

This is a large, impressive dataset—but it’s not a perfectly representative slice of humanity.

• Participants were self-selected consumers who bought Withings devices; the sample skewed toward developed regions and likely higher socioeconomic status, and in this dataset participants were predominantly male. (Nature)

• The sleep sensor tends to overestimate sleep duration and time-to-fall-asleep compared with gold-standard lab sleep studies; if anything, the authors suggest this could mean the share truly meeting sleep recommendations may be even lower than reported. (Nature)

• “Activity” was measured as steps, which misses other meaningful movement (e.g., cycling, swimming, resistance training). (Nature)

Rethinking social protection from the perspective of One Health approach. A case study of the southern Madagascar

 Abstract

We rethink how social protection can function in contexts of rural extreme poverty by applying a One Health lens. Rural households face interlocking risks from climate variability, agriculture, livestock, health, and nutrition, yet programs are usually designed one sector at a time. We introduce a practical way to apply One Health to social protection design and assessment, treating human, animal, and environmental health as a single, connected system.

The approach is tested in southern Madagascar, where human health challenges (disease, water and food insecurity), animal health challenges (livestock disease, feed and water scarcity), and environmental stressors (drought, flood, wind) routinely coincide. Using a mixed-methods design and original data, we describe the range of social protection mechanisms in place and evaluate how they respond to compound risks that cut across domains.

Two main findings emerge. First, interactions among human, animal, and environmental risks are frequent and mutually reinforcing, producing cascades that deepen vulnerability. Second, existing social protection instruments are poorly matched to these linked risks. Coverage is fragmented, benefits are narrow, timing is often misaligned with hazard cycles, and few interventions integrate animal health or ecosystem services with human welfare. Adopting a One Health perspective can guide more effective, shock-responsive social protection in rural settings.

https://www.tandfonline.com/doi/full/10.1080/17565529.2025.2498145

https://hal.science/hal-05066683

Yes Virginia (and the other states too), there are U.S. bird flu pandemic preparedness efforts!

From the FDA

The U.S. FDA has granted Fast Track Designation to ARCT-2304 (LUNAR-H5N1), a self-amplifying mRNA (sa-mRNA) vaccine developed by Arcturus Therapeutics to combat pandemic influenza A (H5N1). The vaccine is part of the company’s STARR mRNA platform, designed to enable rapid and scalable immunization in response to pandemic threats.

Photo by Ben Moreland on Unsplash

Fast Track status allows for expedited development through increased FDA interaction, rolling submissions, and possible priority review.

The vaccine entered Phase 1 clinical trials in November 2024, enrolling 200 healthy adults aged 18–80 across various U.S. locations. The study examines different dosing schedules and evaluates immune response using standard assays. Interim results are expected in late 2025.

Key features of ARCT-2304 include:

• Self-amplifying mRNA technology requiring smaller doses.

• Lyophilized and refrigerator-stable formulation, easing storage and distribution.

• Enhanced immune response and durability compared to conventional vaccines.

The CDC currently has no approved H5N1 vaccine for public use but has prepared candidate vaccine viruses (CVVs) for rapid production if necessary.

This development aligns with U.S. pandemic preparedness efforts and addresses the lack of vaccines against avian influenza strains like H5N1.

H5N1 Bird Flu Detected at San Bernardino Dairy Farms; Health Officials Urge Caution and Preventive Measures

The H5N1 bird flu virus has been identified at four dairy farms in San Bernardino County, California. Public health officials emphasize that the overall risk to the general public remains relatively low, and no human infections have yet been reported in the area. However, the detection of the virus on local farms underscores the importance of vigilance and preventive measures, given its potential impact on public health and agriculture.

Health authorities emphasize the importance of prevention, recommending residents avoid consuming unpasteurized "raw" milk and undercooked meats, which can harbor the virus if contaminated. Additionally, they advise people working closely with animals, particularly birds or livestock, to wear appropriate protective clothing, maintain good hygiene, and wash hands thoroughly after animal contact.

Although the current threat of human infection is considered low, public health officials stress the importance of recognizing bird flu symptoms, which usually appear within two to eight days after exposure but can take up to ten days. Symptoms include fever, cough, sore throat, nasal congestion, muscle or body aches, headaches, diarrhea, fatigue, eye irritation, and difficulty breathing.

Health authorities continue to monitor the situation closely, stressing that while the likelihood of human infection is currently minimal, vigilance and preventive practices are critical to minimizing potential risks.

See original article for more details

Experts Issue Urgent Warning on Bird Flu: Immediate Action Needed to Prevent Pandemic ‼

Experts are raising an urgent alarm over the current bird flu (H5N1) outbreak, warning that immediate preparedness is critical to prevent a potential pandemic. The H5N1 virus, primarily affecting birds, has spread to mammals and humans, leading to heightened concerns after recent findings suggested the virus might spread more easily and become more dangerous. A Louisiana man recently died after the virus showed signs of evolving within him, marking a concerning milestone. Health authorities, including the World Health Organization, have prioritized bird flu as a pathogen with pandemic potential, emphasizing the need for improved global preparedness. Scientists urge rapid action, recommending expanded use of mRNA vaccine technology, similar to COVID-19 vaccines, and advocate establishing mechanisms to ensure equitable vaccine distribution globally.

See original article for more details 

Bird Flu Outbreak (H5N1): Recommended Precautions

The current bird flu outbreak, known as H5N1, primarily affects birds and can cause severe illness and high mortality in them. Although humans and other animals, such as cows, can contract the virus, the current risk to the general public is low, and there have been no confirmed cases of human-to-human transmission. Humans typically contract bird flu through direct or indirect contact with infected birds or their fluids. Symptoms are similar to other types of influenza, including cough, fever, muscle aches, and sore throat. To reduce the risk, avoid contact with sick or dead birds, ensure thorough cooking of meat and eggs, consume pasteurized dairy products, and practice proper hygiene.