Niilo Ryti

M.D, PhD
Docent of Disaster Medicine
Disaster Medicine | Public Health Medicine | Epidemiology

Research Unit of Translational Medicine
Faculty of Medicine

Niilo Ryti is a physician and Docent of Disaster Medicine at the University of Oulu and Adjunct Professor (Docent) of Epidemiology at the University of Helsinki. He is a specialist in anaesthesiology and intensive care medicine and in public health medicine. His work focuses on the environmental epidemiology of natural hazards and climate‑related health impacts, emphasising prediction, prevention, preparedness and the management of extreme events in health systems. He works with ministries, wellbeing services counties and international partners on questions of health system preparedness, climate‑related health risks and the use of data and new technologies.

Researcher information

Researcher profiles

Scientific merits

70+ publications in international peer reviewed journals; H-index 32; >9.000 citations; >34.000 reads. Selected works:

Hundessa S, et al. Global excess deaths associated with heatwaves in 2023 and the contribution of human-induced climate change. The Innovation 2025;6(10):101110.
Urban A, et al. The effectiveness of heat prevention plans in reducing heat-related mortality across Europe. Environmental Research Letters. 2025 Dec 1;20(12):124071. doi: 10.1088/1748-9326/ae2775.
Zhou L, et al. Associations of ambient exposure to benzene, toluene, ethylbenzene, and xylene with daily mortality: a multicountry time-series study in 757 global locations. The Lancet Planetary Health. 2025 Sep;9(9):101306. doi: 10.1016/j.lanplh.2025.101306. Epub 2025 Sep 16. PMID: 40972622.
Yu W, et al. Anthropogenic climate change contributed to excess dengue risk related to hydrometeorological conditions in Brazil and China. One Earth. 2025; DOI: 10.1016/j.oneear.2025.101388.
Wu Y, et al. Estimating the urban heat- related mortality burden due to greenness: a global modelling study. The Lancet Planetary Health. 2025; DOI: 10.1016/S2542-5196(25)00062-2.
Kim Y, et al. A nationwide epidemiological study on the associations between ambient particulate matter and suicide in Finland. Nature Mental Health. 2024; https://doi.org/10.1038/s44220-024-00216-2. 
Lee W, et al. Association of holidays and the day of the week with suicide risk: multicountry, two stage, time series study. British Medical Journal. 2024; 387 doi: https://doi.org/10.1136/bmj-2024-077262. 
He C, et al. Rainfall events and daily mortality across 645 global locations: two stage time series analysis. British Medical Journal. 2024;387:e080944. doi: https://doi.org/10.1136/bmj-2024-080944. 
Yang D, et al. Temporal change in minimum mortality temperature under changing climate. A multicountry multicommunity observational study spanning 1986–2015. Environmental Epidemiology. 2024;8(6):e334 (published in the MCC Article Collection). doi: 10.1097/EE9.0000000000000334.
Chen G, et al. All-cause, cardiovascular, and respiratory mortality and wildﬁre-related ozone: a multicountry two-stage time series analysis. The Lancet Planetary Health. 2024;8(7):e452-e462. oi: 10.1016/S2542-5196(24)00117-7.
Alahmad B, et al. Extreme temperatures and stroke mortality: evidence from a multi-country analysis. Stroke. 2024;55(7):1847-1856. oi: 10.1161/STROKEAHA.123.045751.
Scovronick N, et al Temperature-mortality associations by age and cause: a multi-country multi-city study. Environmental Epidemiology. 2024;8(5):e336. doi: 10.1097/EE9.0000000000000336.
Hundessa S, et al. Global and regional cardiovascular mortality attributable to nonoptimal temperatures over time. Journal of the American College of Cardiology. 2024;83(23):2276-2287. doi: 10.1016/j.jacc.2024.03.425.
Zhao Q, et al. Global, regional, and national burden of heatwave-related mortality from 1990 to 2019: a three-stage modelling study. PLoS Medicine. 2024;21(5):e1004364. doi: 10.1371/journal.pmed.1004364.
Wen B, et al. Comparison for the effects of different components of temperature variability on mortality: a multi-country time- series study. Environment International. 2024;187:108712. doi: 10.1016/j.envint.2024.108712.
Gao Y, et al. Global, regional, and national burden of mortality associated with cold spells during 2000-19: a three-stage modelling study. The Lancet Planetary Health. 2024;8(2):e108-e116. doi: 10.1016/S2542-5196(23)00277-2.
Yu W, et al. Ambient ﬁne particulate matter and daily mortality: a comparative analysis of observed and estimated exposure in 347 cities. International Journal of Epidemiology. 2024;53(3):dyae066. doi: 10.1093/ije/dyae066
Wu Y, et al. Temperature frequency and mortality: assessing adaptation to local temperature. Environment International. 2024;187:108691. doi: 10.1016/j.envint.2024.108691.
Chen K, et al. Impact of population aging on future temperature-related mortality at different global warming levels. Nature Communications. 2024;15(1):1796. doi: 10.1038/s41467-024-45901-z.
Orlov A, et al. Impacts of land-use and land-cover changes on temperature-related mortality. Environmental Epidemiology. 2024;8(6):337. doi: 10.1097/EE9.0000000000000337.
Madaniyazi L, et al. Seasonality of mortality under climate change: a multicountry projection study. The Lancet Planetary Health. 2024;8:e86-e94. doi: 10.1016/S2542-5196(23)00269-3
Stafoggia M, et al. Joint effect of heat and air pollution on mortality in 620 cities of 36 countries. Environment International. 2023;181:108258. doi: 10.1016/j.envint.2023.108258.
Schwarz M, et al. Temporal variations in the short-term effects of ambient air pollution on cardiovascular and respiratory mortality: a pooled analysis of 380 urban areas over a 22-year period. The Lancet Planetary Health. 2024;8(9):e657-e665. doi: 10.1016/S2542-5196(24)00168-2.
Guo Q, et al. Regional variation in the role of humidity on city-level heat- related mortality. PNAS Nexus. 2024;3(8):page290. doi: 10.1093/pnasnexus/pgae290
Liu C, et al. Interactive effects of ambient ﬁne particulate matter and ozone on daily mortality in 372 cities: two stage time series analysis. British Medical Journal. 2023;383:e075203. doi: 10.1136/bmj-2023-075203.
Eunice Lo YT, et al. Optimal heat stress metric for modelling heat-related mortality varies from country to country. International Journal of Climatology. 2023; doi:10.1002/joc.8160.
O’Brien E, et al. Short-Term Association between Sulfur Dioxide and Mortality: A Multicountry Analysis in 399 Cities. Environmental Health Perspectives. 2023; https://doi.org/10.1289/ EHP11112.
Masselot P, et al. Excess mortality attributed to heat and cold: a health impact assessment study in 854 cities in Europe. The Lancet Planetary Health. 2023; https://doi.org/10.1016/ S2542-5196(23)00023-2.
Vaičiulis V, et al. Risk of ischemic and hemorrhagic stroke in relation to cold spells in four seasons. BMC Public Health. 2023;23:553: https://doi.org/10.1186/s12889-023-15459-4. 
Rai M, et al. Heat-related cardiorespiratory mortality: Effect modiﬁcation by air pollution across 482 cities from 24 countries. Environment International. 2023; 174:107825. doi: 10.1016/j.envint.2023.107825.
Alahmad B, et al. Associations Between Extreme Temperatures and Cardiovascular Cause-Specific Mortality: Results From 27 Countries. Circulation. 2022; 146:00-00.
Nottmeyer L, et al. The association of COVID-19 incidence with temperature, humidity, and UV radiation – A global multi-city analysis. Science of the Total Environment. 2022; 854(1):158636.
Choi HM, et al. Effect modification of greenness on the association between heat and mortality: A multi-city multi-country study. eBioMedicine 2022; 84:104251.
Liu C, et al. Coarse Particulate Air Pollution and Daily Mortality: A Global Study in 205 Cities. American Journal of Respiratory and Critical Care Medicine. 2022; 206(8):999-1007.
Wu Y, et al. Global, regional, and national burden of mortality associated with short-term temperature variability from 2000–19: a three-stage modelling study. Lancet Planetary Health. 2022; 6(5):e410-e421.
Lavigne E, et al. Short-term exposure to ambient air pollution and individual emergency department visits for COVID-19: a case-crossover study in Canada. Thorax. 2022; 0:1-8.
Ryti NRI, et al. Cold Weather and Cardiac Arrest in 4 Seasons: Helsinki, Finland, 1997‒2018. American Journal of Public Health. 2022; 112(1):107-115.
Masselot P, et al. Differential Mortality Risks Associated With PM2.5 Components: A Multi-Country, Multi-City Study. Epidemiology. 2022; 33(2):167-175..
Mistry M, et al. Comparison of weather station and climate reanalysis data for modelling temperature-related mortality. Scientific Reports. 2022; 12:5178.
Tobías A, et al. Geographical Variations of the Minimum Mortality Temperature at a Global Scale: A Multicountry Study. Environmental Epidemiology. 2021; 5(5):e169.
Chen G, et al. Mortality risk attributable to wildfire-related PM2.5 pollution: a global time series study in 749 locations. Lancet Planetary Health. 2021 Sep; 5(9):e579-e587.
Vaičiulis V, et al. Association between winter cold spells and acute myocardial infarction in Lithuania 2000–2015. Scientific Reports. 2021; 11:17062.
Heibati B, et al. Weather Conditions and COVID-19 Incidence in a Cold Climate: A Time-Series Study in Finland. Frontiers Public Health. 2021; 8:605128.
Jaakkola JJK, et al. Airborne pollen concentrations and daily mortality from respiratory and cardiovascular causes. European Journal of Public Health. 2021 Oct 11; 31(4):722-724.
Zhao Q, et al. Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study. Lancet Planetary Health. 2021; 5(7):e415-e425. [Top 10th climate paper in 2021 for news and media attention by Carbon Brief]
Vicedo-Cabrera AM, et al. The burden of heat-related mortality attributable to recent human-induced climate change. Nature Climate Change. 2021; 11(6):492-500. [Top 1st climate paper for 2021 for news and social media attention by Carbon Brief]
Sera F, et al. A cross-sectional analysis of meteorological factors and SARS-CoV-2 transmission in 409 cities across 26 countries. Nature Communications 2021; 12:5968.
Urban A, et al. Evaluation of the ERA5 reanalysis-based Universal Thermal Climate Index on mortality data in Europe. Environmental Research. 2021; 198:111227.
Chen K, et al. Ambient carbon monoxide and daily mortality: a global time-series study in 337 cities. Lancet Planet Health. 2021; 5(4):e191-e199.
Meng X, et al. Short term associations of ambient nitrogen dioxide with daily total, cardiovascular, and respiratory mortality: multilocation analysis in 398 cities. BMJ. 2021; 372:n534.
Madaniyazi L, et al. Seasonal variation in mortality and the role of temperature: a multi-country multi-city study. International Journal of Epidemiology. 2021; 51(1):122-133.
Hintsala HE, et al. Central aortic hemodynamics following acute lower and upper‑body exercise in a cold environment among patients with coronary artery disease. Scientific Reports. 2021; 11:2550.
Lee W, et al. Projections of excess mortality related to diurnal temperature range under climate change scenarios: a multi-country modelling study. Lancet Planetary Health. 2020; 4: e512–21.
Balogun HA, et al. Effects of Air Pollution on the Risk of Low Birth Weight in a Cold Climate. Appl Sci. 2020; 10(18):6399.
Ryti NRI, et al. Paradoxical home temperatures during cold weather: a proof-of-concept study. International Journal of Biometeorology. 2020; 64:2065–2076.
Siddika N, et al. Short-term prenatal exposure to ambient air pollution and risk of preterm birth - A population-based cohort study in Finland. Environmental Research. 2020; 184:109290.
Valtonen RIP, et al. Endothelial function in response to exercise in the cold in patients with coronary artery disease. Clinical Physiology and Functional Imaging. 2020; 40:245–256.
Liu C, et al. Ambient Particulate Air Pollution and Daily Mortality in 652 Cities. New England Journal of Medicine. 2019; 381(8):705-715. [Included in the New England Journal of Medicine 12 Notable Articles of 2019]
Lee JY, et al. Predicted temperature-increase-induced global health burden and its regional variability. Environment International. 2019; 131:105027.
Siddika N, et al. Synergistic effects of prenatal exposure to fine particulate matter (PM2.5) and ozone (O3) on the risk of preterm birth: A population-based cohort study. Environmental Research. 2019; 176:108549.
Ikäheimo TM, et al. Good safety practice in a randomized controlled trial (CadColdEx) involving increased cardiac workload in patients with coronary artery disease. BMC Cardiovascular Disorders. 2019; 19:69.
Sera F, et al. How urban characteristics affect vulnerability to heat and cold: a multi-country analysis. International Journal of Epidemiology. 2019; 48(4):1101-1112.
Ryti NRI, et al. Coronary stenosis as a modifier of the effect of cold spells on the risk of sudden cardiac death: a case-crossover study in Finland. BMJ Open. 2018; 8(8):e020865.
Vicedo-Cabrera AM, et al. Temperature-related mortality impacts under and beyond Paris Agreement climate change scenarios. Climatic Change. 2018; 150(3-4):391-402. [Top 5% of all research outputs ever tracked by Altmetric, measured in 2018]
Guo Y, et al. Quantifying excess deaths related to heatwaves under climate change scenarios: A multi-country time-series modelling study. PLoS Medicine. 2018; 15(7):e1002629.
Valtonen RIP, et al. Cardiovascular Responses to Cold and Submaximal Exercise in Patients with Coronary Artery Disease. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2018; 315(4):R768-R776.
Gasparrini A, et al. Projections of temperature-related excess mortality under climate change scenarios. Lancet Planetary Health. 2018; 1(9):e360-e367.
Ryti NRI, et al. Cold spells and ischaemic sudden cardiac death: effect modification by prior diagnosis of ischaemic heart disease and cardioprotective medication. Scientific Reports. 2017; 7:41060.
Ryti NRI, et al. The risk of sudden cardiac death in relation to season-specific cold spells: a case-crossover study in Finland. BMJ Open. 2017; 7(11):e017398.
Ryti NRI, et al. Global Association of Cold Spells and Adverse Health Effects: A Systematic Review and Meta-Analysis. Environmental Health Perspectives. 2016; 124(1):12-22. [RECTOR'S AWARD]

Contact information

E-mail

niilo.ryti@oulu.fi

Phone number

0407458484

Social media

Keywords

effects of cold and heat on health and human performance epidemiology international environmental research and collaboration issues related to public health