title: The effect of temperature on cardiovascular disease hospital admissions among elderly people in Thai Nguyen Province, Vietnam.
abstract: BACKGROUND
  Projected increases in weather variability due to climate change will have severe consequences on human health, increasing mortality, and disease rates. Among these, cardiovascular diseases (CVD), highly prevalent among the elderly, have been shown to be sensitive to extreme temperatures and heat waves.
  
  
  OBJECTIVE
  This study aimed to find out the relationship between daily temperature (and other weather parameters) and daily CVD hospital admissions among the elderly population in Thai Nguyen province, a northern province of Vietnam.
  
  
  METHODS
  Retrospective data of CVD cases were obtained from a data base of four hospitals in Thai Nguyen province for a period of 5 years from 2008 to 2012. CVD hospital admissions were aggregated by day and merged with daily weather data from this period. Distributed lag non-linear model (DLNM) was used to derive specific estimates of the effect of weather parameters on CVD hospital admissions of up to 30 days, adjusted for time trends using b-splines, day of the week, and public holidays.
  
  
  RESULTS
  This study shows that the average point of minimum CVD admissions was at 26°C. Above and below this threshold, the cumulative CVD admission risk over 30 lag days tended to increase with both lower and higher temperatures. The cold effect was found to occur 4-15 days following exposure, peaking at a week's delay. The cumulative effect of cold exposure on CVD admissions was statistically significant with a relative risk of 1.12 (95% confidence interval: 1.01-1.25) for 1°C decrease below the threshold. The cumulative effect of hot temperature on CVD admissions was found to be non-significant and was estimated to be at a relative risk of 1.17 (95% confidence interval: 0.90-1.52) for 1°C increase in the temperature. No significant association was found between CVD admissions and the other weather variables.
  
  
  CONCLUSIONS
  Exposure to cold temperature is associated with increasing CVD admission risk among the elderly population.
authors.affiliation: Administration of Science technology and Training, Ministry of Health, Hanoi, Vietnam.
authors.forename: Pham Ngan
authors.initials: PN
authors.lastname: Giang
authors.affiliation: Department of Medical Statistics, University of Medicine and Pharmacy at Ho Chi Minh city, Ho Chi Minh City, Vietnam; dvdung@ump.edu.vn.
authors.forename: Do Van
authors.initials: do V
authors.lastname: Dung
authors.affiliation: Institute for Preventive Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam.
authors.forename: Kim
authors.initials: K
authors.lastname: Bao Giang
authors.affiliation: Faculty of Public Health, University of Medicine and Pharmacy, Thai Nguyen, Vietnam.
authors.forename: Hac Van
authors.initials: HV
authors.lastname: Vinhc
authors.affiliation: Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Joacim
authors.initials: J
authors.lastname: Rocklöv
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D057231:Climate Change; D016208:Databases, Factual; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D010343:Patient Admission / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D013696:Temperature; D014744:Vietnam / Q000453:epidemiology; D014887:Weather
keywords: cardiovascular diseases; distributed lag non-linear model; hospital admission; temperature