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📖 Environment & Lifestyle Sources

Sources for environmental factors, lifestyle choices, and external influences on health.

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Key Research Findings Summary​

Light Exposure & Circadian Health​

  • Brighter nights and darker days predict higher mortality — PNAS 2024 study of ~89,000 individuals found those with higher night light and lower day light exposure had increased mortality risk
  • Light at night (LAN) linked to mental health issues — Meta-analysis of 556,861 participants found LAN associated with depression (OR 1.18), anxiety (OR 1.10), bipolar disorder (OR 1.19)
  • Light therapy improves shift worker sleep — Meta-analysis: +32.5 min total sleep time, +2.9% sleep efficiency
  • Nighttime light exposure increases diabetes risk — 8-year study of 84,790 participants

Temperature Therapies​

  • Sauna bathing reduces cardiovascular mortality ~50% — 3-7 sessions/week associated with 37-83% risk reduction for stroke, hypertension, heart attack
  • Dose-response relationship — CVD mortality rates: 1 session/week (10.1 per 1000 person-years), 2-3 sessions (7.6), 4+ sessions (2.7)
  • Combined exercise + sauna more effective than either alone

Cold Exposure (CWI 2025 Meta-Analysis)​

  • Significant acute effects — 530% increase in noradrenaline, 250% increase in dopamine
  • Reduced sickness absence — 29% reduction in those taking cold showers
  • Time-dependent benefits — Stress reduction significant at 12 hours post-CWI
  • Recommended protocol — ~11 minutes/week total (2-4 sessions, 1-5 min each)

Social Connection & Loneliness (2023-2025 Meta-Analyses)​

  • Social isolation increases mortality risk — HR 1.32-1.35 across 90 cohort studies (2.2M individuals)
  • Loneliness independently increases risk — HR 1.14 (95% CI 1.10-1.18)
  • Being socially connected increases survival odds by 50% — Meta-analysis of 148 prospective studies
  • Risk exceeds physical inactivity, obesity, and air pollution

Alcohol - No Benefits from Moderate Drinking​

  • 2024 meta-analysis of 107 studies — No protective effects when adjusted for confounders
  • Earlier "benefits" explained by bias — "Sick quitter" effect in control groups
  • Increased risk at 25g+/day — Significant mortality increase at 45g+/day
  • Larger risks for women — RR 1.22 compared to female lifetime nondrinkers

Nature & Green Space (2024)​

  • Strong evidence for mental health benefits — Meta-analyses confirm reduced depression and anxiety
  • Window views of nature improve health — Ulrich 1984 + recent studies confirm benefits
  • All-cause mortality reduced — Long-term exposure to residential greenness protective

Key Sources​

Source Tiers
  • Tier A: Meta-analyses, systematic reviews, large-scale RCTs
  • Tier B: Professional guidelines, institutional resources
  • Tier C: Individual experts, researchers
  • Tier D: Popular science books

Light & Circadian​

  • Brighter nights, darker days predict mortality — PNAS (2024) — Tier A
    • ~89,000 individuals; light sensor data; mortality risk
  • Light at night and mental health meta-analysis — ScienceDirect (2025) — Tier A
    • 556,861 participants; 19 studies; depression, anxiety, bipolar
  • Light therapy for shift workers — Scientific Reports (2024) — Tier A
    • 11 studies; improved sleep time and efficiency
  • Evening light exposure and sleep — SAGE Journals (2022) — Tier A
    • Meta-analysis; polysomnographic outcomes

Temperature Therapies​

Sauna Research

  • Sauna and cardiovascular mortality — PMC (2018) — Tier A
    • 15-year follow-up; dose-response relationship
  • Sauna mechanisms review — Mayo Clinic Proceedings (2018) — Tier A
    • Cardiovascular and health benefits
  • Sauna and peripheral arterial disease — Frontiers in CV Med (2025) — Tier A
    • Novel management approach
  • Combined exercise and sauna — Am J Physiol (2022) — Tier A

Cold Exposure Research

  • Cold-water immersion meta-analysis — PLOS One (2025) — Tier A
    • Systematic review; time-dependent effects; 29% sickness reduction
  • Cold exposure neurohormesis — J Neuropsychiatry (2024) — Tier A
    • 530% noradrenaline, 250% dopamine increase
  • Cold water therapy for healthy aging — PMC (2025) — Tier A
    • Lifestyle intervention potential

Social Connection​

  • 90 cohort studies on social isolation/loneliness — Nature Human Behaviour (2023) — Tier A
    • 2.2M individuals; mortality risk
  • Social isolation and all-cause mortality — PLOS One (2023) — Tier A
    • Systematic review and meta-analysis
  • Loneliness in older adults — Aging Clinical & Experimental Research (2025) — Tier A
    • 86 studies; HR 1.14-1.35
  • Social connection and survival — PLOS Medicine (2010) — Tier A
    • 148 studies; 50% increased survival odds
  • Social Isolation and Mortality — Holt-Lunstad (2015) — Tier A
  • Loneliness and Health Outcomes — Hawkley & Cacioppo (2010) — Tier A

Alcohol & Substances​

  • No benefits from moderate drinking — JAMA Network Open (2023) — Tier A
    • 107 studies; adjusted for abstainer bias
  • Alcohol consumption and all-cause mortality — PMC (2023) — Tier A
    • Systematic review; increased risk at 25g+/day
  • Alcohol and health outcomes umbrella review — PMC (2022) — Tier A
  • Alcohol Use Disorder risk — Addiction (2024) — Tier A
    • Dose-response relationship

Nature & Green Space​

  • Credibility of green space evidence — Lancet eBioMedicine (2024) — Tier A
    • Overview of meta-analyses; evidence grading
  • Window views of nature — BioScience (2024) — Tier A
    • Meta-analysis; health benefits
  • Green space and mental health — Nature (2024) — Tier A
    • Disadvantaged populations; systematic review
  • Green space morphology and health — Lancet Planetary Health (2024) — Tier A
  • European greenspace scoping review — SSPH Journal (2024) — Tier A
Sources by Topic (Click to expand)

Light & Circadian (light-circadian.md)​

  • PNAS 2024 mortality study
  • Light at night mental health meta-analysis
  • Light therapy for shift workers
  • Brown recommendations

Temperature (temperature.md)​

  • Sauna cardiovascular meta-analyses
  • Cold-water immersion PLOS One 2025
  • Neurohormesis research

Social Connection (social-connection.md)​

  • Nature Human Behaviour 90-study meta-analysis
  • Holt-Lunstad mortality meta-analysis
  • Social connection survival odds

Alcohol & Caffeine (alcohol-caffeine.md)​

  • JAMA Network Open 2023 (no moderate drinking benefits)
  • Abstainer bias research

Air Quality (air-quality.md)​

  • WHO guidelines
  • Environmental health institutions

Environment Optimization (optimization.md)​

  • Green space meta-analyses
  • Window view benefits
  • Combined lifestyle factors
Best Entry Points by Topic
  1. For light/circadian: PNAS 2024 mortality study + Brown recommendations
  2. For social connection: Nature Human Behaviour 90-study meta-analysis
  3. For temperature therapies: Mayo Clinic sauna review + PLOS One CWI meta-analysis
  4. For alcohol: JAMA Network Open 2023 (Stockwell et al.)
  5. For green space: Lancet eBioMedicine 2024 credibility overview

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