Heatwaves on Human Morbidity in Primary Care Settings: Comparison
View Latest Version
Please note this is a comparison between Version 1 by Mahmoud Alsaiqali and Version 2 by Beatrix Zheng.

Heatwaves are expected to be more intense, occur more often, and last longer. There is a need to study the effects of heatwaves in primary care settings. Heatwaves are associated with increased heat-related morbidities and decreased respiratory infection risk. The study of heatwaves’ effects in primary care settings helps evaluate the impact of heatwaves on the general population. Primary care settings might be not suitable to study acute life-threatening morbidities. 

  • heatwaves
  • primary care
  • case-crossover

1. Introduction

According to the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment Report (AR5), global warming is unequivocal. The last 30 years were probably the warmest of the last 1400 years in the Northern Hemisphere, and the temperature is expected to rise further over the 21st century. According to the same report, heatwaves, which are prolonged periods of extremely high temperature, are expected to be more intense, occur more often, and last longer [1].
Most previous studies showed that heatwaves are associated with increased overall morbidity. Results for the effect of heatwaves on specific morbidities showed inconsistencies [2]. For example, Turner et al. [3] showed that heatwaves are associated with increased ambulance attendance for cardiovascular and respiratory diseases, especially in the elderly population. Meanwhile, Wang et al. [4] found an increase in emergency hospital admissions (EHAs) from non-external causes (not caused by out-of-human body causes) and renal diseases but not cardiovascular or respiratory diseases. The effect of heatwaves was more pronounced in the vulnerable population such as children and the elderly [3][4][5][6][7], people with chronic diseases [4][8][9], and people with low socioeconomic status [10][11].
To date, most research on the effect of heatwaves on morbidity is based on hospital and emergency care data, and research using primary care data are limited [12][13][14][15]. During the heatwave of summer 2013 in England, the number of general practice (GP) consultations increased for heat illnesses compared with similar periods in non-heatwave years (2012, 2014). No increase was detected for asthma, breathing difficulties, cerebrovascular accidents, or cardiovascular symptoms consultations [12][13]. A case-crossover analysis of the effect of ambient temperature on heat-related morbidities among type-2 diabetics showed that increased temperature is associated with increased GP consultation [15]. Primary care is the first contact point for individuals with a health problem and it directly addresses most of their healthcare needs throughout their life. Therefore, studies using data from primary healthcare are needed to cover a wider population and morbidities including mild diseases and symptoms.
In this study, we investigated the short-term effects of heatwaves on the incidence of selected morbidities among patients attending primary care in Flanders (Belgium) between the years 2000 and 2015. We also studied to what extent the effect is modified by age and premorbid chronic medical conditions such as diabetes and hypertension. We hypothesized that heatwaves are associated with an increased incidence of selected acute morbidities in primary care (detailed in the Methods section) and that increased age, and having premorbid medical conditions increase that risk.

2. Current Insights

The effect of heat waves on selected morbidities within primary care settings was studied. Heatwaves were associated with an increased incidence of heat-related morbidities such as heat stroke and dehydration. Heatwaves were associated with a decreased incidence of respiratory infections. For the cardiovascular group, it was only significant for Transient cerebral ischaemia (K89) and Stroke/cerebrovascular accident (K90). There was no significant interaction by age or premorbid chronic medical condition (DM, HTN).
Our findings of increased heat-related morbidities in heatwaves are logical and in line with previous research [8][16][17][18]. For example, during the 2006 heatwaves in California, hospitalizations for heat-related illnesses increased by 10 times [8]. This supports the validity of our method as we see the result where we expect to see it.
For the cardiovascular group, we noted that, with increasing lag, the risk of TIA is decreasing, and the risk of stroke is increasing. This might be explained by the fact the neurological symptoms should remain for a certain period (>24 h) to be diagnosed as a stroke. Our finding is supported by previous research. For example, a case-crossover study showed that extreme high temperature over the last 3 days is associated with increased risk for both ischemic (OR = 1.18; 95% CI: 1.07–1.36) and hemorrhagic strokes (OR = 1.34; 95% CI: 1.26–1.42) [19]. A recent review article concluded that, despite some inconsistencies, there is supporting evidence that temperature is associated with increased stroke risk with the hot temperature tends to have a more immediate effect (i.e., short lag between the exposure and the event) [20].
For the other cardiovascular morbidities studied, we did not see a significant effect. Previous literature showed inconsistent results [3][4][9][21]. In our study, this might be explained by the fact that patients with more serious diseases might head to the emergency department directly and, as a result, are missing in the primary care dataset.
In the respiratory group, our results showed that heatwaves were associated with a lower incidence of respiratory infections. In general, respiratory infections show clear seasonality and are usually related to cold weather. This might be related to the effect of heat on viral replication and transmission. Previous research showed that respiratory viruses’ replication and transmission are dependent on relative humidity and temperature; namely, it is more present in cold dry conditions. Air transmission efficiency decreased with increased temperature to reach an undetected level at 30 °C [22][23][24][25]. This might explain the reduced incidence of respiratory infection during heatwaves seen in our results. In addition, the patients may decide to not visit their physicians, especially if the symptoms are mild. For asthma and COPD, there was no significant increase during heatwaves. The previous literature showed inconsistent results [26][27][28]. In our study, this might be explained by the fact that there is no specific code for asthma or COPD exacerbation. Patients coming for a regular check-up and medication refill, as well as exacerbation, are registered with the same code in the dataset.
No significant interaction by age or having chronic diseases (DM, HTN) was found. The majority of previous research showed that the elderly are more susceptible to the effect of heatwaves [4][5][6][29][30]. The result of the effect modification by premorbid chronic conditions showed inconsistent results [16][31][32]. Our findings could be related to the fact that we studied the effect in the primary care settings not the emergency settings and the population characteristics differ from the ones studied in previous research. This might be a reassuring finding that vulnerable populations receive the heatwave warnings and take the appropriate precautions to protect themselves during heatwaves.

References

  1. Intergovernmental Panel on Climate Change. Climate Change 2014 Mitigation of Climate Change; Cambridge University Press: Cambridge, UK, 2014.
  2. Li, M.; Gu, S.; Bi, P.; Yang, J.; Liu, Q. Heat waves and morbidity: Current knowledge and further direction—A comprehensive literature review. Int. J. Environ. Res. Public Health 2015, 12, 5256–5283.
  3. Turner, L.R.; Connell, D.; Tong, S. The Effect of Heat Waves on Ambulance Attendances in Brisbane, Australia. Prehospital Disaster Med. 2013, 28, 482–487.
  4. Wang, X.Y.; Barnett, A.G.; Yu, W.; FitzGerald, G.; Tippett, V.; Aitken, P.; Neville, G.; McRae, D.; Verrall, K.; Tong, S. The impact of heatwaves on mortality and emergency hospital admissions from non-external causes in Brisbane, Australia. Occup. Environ. Med. 2011, 69, 163–169.
  5. Schaffer, A.; Muscatello, D.; Broome, R.; Corbett, S.; Smith, W. Emergency department visits, ambulance calls, and mortality associated with an exceptional heat wave in Sydney, Australia, 2011: A time-series analysis. Environ. Health 2012, 11, 3.
  6. Johnson, H.; Kovats, S.; McGregor, G.; Stedman, J.; Gibbs, M.; Walton, H.; Cook, L. The Impact of the 2003 Heat Wave on Mortality and Hospital Admissions in England. Epidemiology 2004, 15, S126.
  7. Wang, X.-Y.; Barnett, A.; Guo, Y.-M.; Yu, W.-W.; Shen, X.-M.; Tong, S.-L. Increased risk of emergency hospital admissions for children with renal diseases during heatwaves in Brisbane, Australia. World J. Pediatrics 2014, 10, 330–335.
  8. Knowlton, K.; Rotkin-Ellman, M.; King, G.; Margolis, H.G.; Smith, D.; Solomon, G.; Trent, R.; English, P. The 2006 California heat wave: Impacts on hospitalizations and emergency department visits. Environ. Health Perspect. 2009, 117, 61–67.
  9. Williams, S.; Nitschke, M.; Weinstein, P.; Pisaniello, D.L.; Parton, K.A.; Bi, P. The impact of summer temperatures and heatwaves on mortality and morbidity in Perth, Australia 1994–2008. Environ. Int. 2012, 40, 33–38.
  10. Kravchenko, J.; Abernethy, A.P.; Fawzy, M.; Lyerly, H.K. Minimization of Heatwave Morbidity and Mortality. Am. J. Prev. Med. 2013, 44, 274–282.
  11. Wichmann, J.; Andersen, Z.J.; Ketzel, M.; Ellermann, T.; Loft, S. Apparent temperature and cause-specific mortality in Copenhagen, Denmark: A case-crossover analysis. Int. J. Environ. Res. Public Health 2011, 8, 3712–3727.
  12. Smith, S.; Elliot, A.J.; Hajat, S.; Bone, A.; Smith, G.E.; Kovats, S. Estimating the burden of heat illness in England during the 2013 summer heatwave using syndromic surveillance. J. Epidemiol. Community Health 2016, 70, 459–465.
  13. Smith, S.; Elliot, A.J.; Hajat, S.; Bone, A.; Bates, C.; Smith, G.E.; Kovats, S. The Impact of Heatwaves on Community Morbidity and Healthcare Usage: A Retrospective Observational Study Using Real-Time Syndromic Surveillance. Int. J. Environ. Res. Public Health 2016, 13, 132.
  14. Vashishtha, D.; Sieber, W.; Hailey, B.; Guirguis, K.; Gershunov, A.; Al-Delaimy, W.K. Outpatient clinic visits during heat waves: Findings from a large family medicine clinical database. Fam. Pract. 2018, 35, 567–570.
  15. Hajat, S.; Haines, A.; Sarran, C.; Sharma, A.; Bates, C.; Fleming, L.E. The effect of ambient temperature on type-2-diabetes: Case-crossover analysis of 4+ million GP consultations across England. Environ. Health 2017, 16, 73.
  16. Semenza, J. Excess hospital admissions during the July 1995 heat wave in Chicago. Am. J. Prev. Med. 1999, 16, 269–277.
  17. Sheridan, S.C.; Lin, S. Assessing Variability in the Impacts of Heat on Health Outcomes in New York City Over Time, Season, and Heat-Wave Duration. EcoHealth 2014, 11, 512–525.
  18. Nitschke, M.; Tucker, G.R.; Hansen, A.L.; Williams, S.; Zhang, Y.; Bi, P. Impact of two recent extreme heat episodes on morbidity and mortality in Adelaide, South Australia: A case-series analysis. Environ. Health 2011, 10, 42.
  19. Chen, J.-h.; Jiang, H.; Wu, L.; Liao, X.; Lu, Y.; Tao, X.-Q.; Deng, P.-F.; Long, Y.; Huang, H.-l. Association of ischemic and hemorrhagic strokes hospital admission with extreme temperature in Nanchang, China—A case-crossover study. J. Clin. Neurosci. 2017, 43, 89–93.
  20. Lavados, P.M.; Olavarría, V.V.; Hoffmeister, L. Ambient Temperature and Stroke Risk. Stroke 2018, 49, 255–261.
  21. Ma, W.; Xu, X.; Peng, L.; Kan, H. Impact of extreme temperature on hospital admission in Shanghai, China. Sci. Total Environ. 2011, 409, 3634–3637.
  22. Lowen, A.C.; Mubareka, S.; Steel, J.; Palese, P. Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog. 2007, 3, 1470–1476.
  23. Lowen, A.C.; Steel, J.; Mubareka, S.; Palese, P. High temperature (30 degrees C) blocks aerosol but not contact transmission of influenza virus. J. Virol. 2008, 82, 5650–5652.
  24. Lowen, A.C.; Steel, J. Roles of humidity and temperature in shaping influenza seasonality. J. Virol. 2014, 88, 7692–7695.
  25. Pica, N.; Bouvier, N.M. Ambient Temperature and Respiratory Virus Infection. Pediatric Infect. Dis. J. 2014, 33, 311–313.
  26. Xu, Z.; Huang, C.; Hu, W.; Turner, L.R.; Su, H.; Tong, S. Extreme temperatures and emergency department admissions for childhood asthma in Brisbane, Australia. Occup. Environ. Med. 2013, 70, 730–735.
  27. Wang, Y.-C.; Lin, Y.-K. Temperature effects on outpatient visits of respiratory diseases, asthma, and chronic airway obstruction in Taiwan. Int. J. Biometeorol. 2014, 59, 815–825.
  28. Figgs, L.W. Emergency department asthma diagnosis risk associated with the 2012 heat wave and drought in Douglas County NE, USA. Heart Lung 2019, 48, 250–257.
  29. Hansen, A.; Bi, P.; Nitschke, M.; Ryan, P.; Pisaniello, D.; Tucker, G. The effect of heat waves on mental health in a temperate Australian city. Environ. Health Perspect. 2008, 116, 1369–1375.
  30. Ha, S.; Talbott, E.O.; Kan, H.; Prins, C.A.; Xu, X. The effects of heat stress and its effect modifiers on stroke hospitalizations in Allegheny County, Pennsylvania. Int. Arch. Occup. Environ. Health 2013, 87, 557–565.
  31. Schwartz, J. Who is Sensitive to Extremes of Temperature? Epidemiology 2005, 16, 67–72.
  32. Hansen, A.L.; Bi, P.; Ryan, P.; Nitschke, M.; Pisaniello, D.; Tucker, G. The effect of heat waves on hospital admissions for renal disease in a temperate city of Australia. Int. J. Epidemiol. 2008, 37, 1359–1365.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
Video Production Service
Feedback