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Winter

Winter has been studied in 11 papers since 2016: 9 observational studies in people, 2 in animals; 2 in the past year.

Exposure

11 papers study it9 findingsUpdated

See all 10

“less mobile individuals aged 80-99 years had higher rates of fractures in winter.”
Weather and hip fractures: A nine-year study across England and WalesInjury2025doi:10.1016/j.injury.2025.112856

None of its findings points the other way.

C, W, M, H: cells, worms or flies, mice, humans. Dark: independent labs found the same change there. Light: one lab or one study. Outline: nothing yet.

Labs are independent when their papers share no last author and no institution.

Company ties: findings with an author at a company, or from a paper whose competing-interests statement declares ties to one.

  • 8 independent labs in 6 countries
  • Funders: Human Frontier Science Program and others
  • 1 of 9 findings with company ties
  • Humans8
  • Animals2

What did studies of Winter find?

3

Studies of Winter measured 3 outcomes; the most studied are BDNF (1 study), sleep fragmentation (1) and mortality (1).

BDNF

downin humans1

1 study

  1. Winter is linked with lower BDNF in humans (from the start to the end of winter).

    “Plasma BDNF decreased from the first to the second assessment.”

    Humansfrom the start to the end of winterplasmawintern = 17

    The winter is coming: seasonal variations in BDNF levels among older adults in a high-latitude region - a preliminary study

    Frontiers in psychiatry

More on BDNF

Sleep fragmentation

upin humans1

1 study

  1. Winter is linked with higher sleep fragmentation in humans.

    “Total Sleep Time was longer in winter (7.26 hours, SD = 1.0) compared to summer (6.40 hours, SD = 0.88), but so were Fragmentation Index and Wake After Sleep Onset.”

    Humansn = 114

    Winter sleep extension and fragmentation in a South African agropastoral community

    Sleep health

Mortality

upin humans1+11%

1 study

  1. Winter is linked with higher mortality in humans during 2000-2019 (+11%).

    “During 2000-2019, winter mortality rates for men and women were 11% and 14% higher than expected based on non-winter rates.”

    Humansduring 2000-2019males

    Excess winter mortality in Finland, 1971-2019: a register-based study on long-term trends and effect modification by sociodemographic characteristics and pre-existing health conditions

    BMJ open

What is Winter linked with?

5

Studies link Winter with 5 measures, most often cardiovascular mortality (1 study), hip fracture (1) and apoptosis (1).

Cardiovascular mortality

upin humans1+14%

1 study

  1. Winter is linked with a higher risk of cardiovascular mortality in humans (13.6%).

    “The overall winter excess cardiovascular mortality was 13.6%.”

    Humans

    Seasonal Disparities in Cardiovascular Mortality: Analyzing Winter Excess Across Demographics and Regions (2018–2023)

    AHA Scientific Sessions 2025 abstract

Hip fracture

upin humans1

1 study

  1. Winter is associated with hip fracture in humans (less mobile individuals).

    “less mobile individuals aged 80-99 years had higher rates of fractures in winter.”

    Humansless mobile individuals

    Weather and hip fractures: A nine-year study across England and Wales

    Injury

More on Hip fracture

Apoptosis

mixedin S. araneus1

1 study

  1. Winter is associated with apoptosis in S. araneus.

    “We discovered seasonal variation in suites of genes involved in energy homeostasis and apoptosis”

    Animalshypothalamus

    Seasonal and comparative evidence of adaptive gene expression in mammalian brain size plasticity

    eLife

More on Apoptosis

Cardiovascular disease events

upin humans1

1 study

  1. Winter is associated with cardiovascular disease events in humans (BRHS and PROSPER).

    “More CVD events were registered in winter in both studies.”

    HumansBRHS and PROSPER

    Effect of cold spells and their modifiers on cardiovascular disease events: Evidence from two prospective studies

    International journal of cardiology

More on Cardiovascular disease events

Geriatric fracture incidence

upin humans1

1 study

  1. Winter is associated with geriatric fracture incidence in humans (December to February).

    “Nevertheless, it showed a higher incidence of fractures in winter, from December to February.”

    HumansDecember to February1 January 2012 to 31 December 2013n = 676

    Influence of the Weather on the Incidence of Fractures in the Elderly

    Acta chirurgiae orthopaedicae et traumatologiae Cechoslovaca

Funding

4 grants since 2017

National Institute on Aging$3.5MJapan Society for the Promotion of Science¥3.4MNatural Sciences and Engineering Research CouncilCA$21K

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