Who is sensitive to extremes of temperature a case only analysis

Background Citations. Methods Citations. Results Citations. Topics from this paper. Diabetes Mellitus Heart failure Pneumonia. Paper Mentions. News Article. Environmental Health Perspectives. Citation Type. Has PDF. Publication Type. More Filters. Who is more vulnerable to death from extremely cold temperatures? A case-only approach in Hong Kong with a temperate climate. Highly Influenced. View 9 excerpts, cites results and background. Nonwhites had greater risks on both hot 1.

The other conditions conveyed no higher risks than average. Conclusions: Sociodemographic characteristics and medical conditions can increase the likelihood of death associated with temperature extremes.

Abstract Background: Extremes of temperature are well known to be associated with excess mortality. Publication types Research Support, U. O 3 was found to be a confounder especially on hot days [ 18 , 21 ], and other investigators also showed O 3 to be a positive effect modifier of temperature and mortality, at least in some study locations [ 22 , 23 ]. Much of the focus of epidemiologic studies has been identifying cause-specific outcomes and vulnerable subgroups of mortality from high ambient temperature Table 3.

Some investigators have reported greater risks for deaths from cardiovascular CVD [ 5 , 14 , 24 ], respiratory [ 5 , 12 , 24 — 26 ], cerebrovascular [ 16 ], diabetes [ 27 , 28 ], or pre-existing psychiatric disorders [ 16 , 29 , 30 ]. Other studies also showed elevated risk from mortality subcategories of CVD diseases, such as myocardial infarction [ 8 , 14 , 31 ], ischemic heart disease [ 14 ], and congestive heart failure [ 14 , 30 , 32 ],.

Age has been found to modify the association between ambient temperature and mortality. The elderly have been reported to be at greater risk from mortality following heat waves, as well as ambient temperature. In addition to the elderly who were at least 75 years [ 12 ], 70 years [ 31 ] or 65 years [ 5 , 14 , 15 , 19 , 24 — 26 , 33 , 34 ] of age, children under 15 years [ 18 , 33 ], children five years and younger [ 14 ], and infants one year of age and under [ 14 , 35 ] have been identified to be at increased risk for mortality from high ambient temperature.

One investigator also reported 15 to 64 years of age to be at a significantly increased risk, although still lower than the elderly or young children [ 33 ]. Modifications by gender has also been studied, and some investigators reported no difference by gender [ 14 ], while others found men in Santiago and Sao Paulo [ 15 ] specifically for circulatory causes [ 35 ] or women in various locations [ 15 — 17 , 19 , 24 , 36 ] to be at higher risk for mortality.

Other recent epidemiologic studies also reported Black racial ethnic group [ 14 , 37 ] and non-Whites [ 28 ] to be at greater risk than Whites in the US.

Hispanic subgroups, however, have not been identified as being at greater risk in one study, partially explained by more social networking among this ethnic group [ 14 ]. Other factors that provoked greater risk included indicators for lower socioeconomic status, including the less educated, persons living in lower income areas [ 16 ] and dying out of the hospital [ 14 , 27 , 38 ].

Also, increased poverty [ 39 ], and lack of air conditioner [ 11 , 37 , 39 ] were observed risk factors. However, lower socioeconomic status [ 33 ] and education level were not found to be a risk factor in all studies [ 14 ]. Some studies reported variation by latitude, supporting the evidence for acclimatization. People who live in cities where the temperatures are generally elevated in the summer were found to have higher minimum mortality temperatures, or less risk given the same level of temperature, than people who live in cities with milder climates [ 7 , 21 , 39 ].

A similar finding was reported in California, where slightly higher estimates were found for coastal counties where milder temperatures are generally experienced [ 6 ].

Although coastal areas in California are usually more expensive, many of the homes lack air conditioning, since they have not been needed. Therefore, air conditioning prevalence is not an indicator of socioeconomic status in California, as it is in the remainder of the U.

In the past few years, several epidemiologic studies have been conducted in various locations to characterize temperature and mortality. In the US, similar effects were found in nine counties in California and in nine counties outside of California in two separate studies using the same methods [ 6 , 7 ]. In Europe and Korea, however, the effect estimates were larger [ 12 , 40 ], further supporting the need to conduct temperature-mortality studies for specific areas.

The results from future studies can be more readily compared if estimates are reported per degree Celsius or Fahrenheit per unit change in temperature assuming linearity , or if a regression coefficient is given, rather than selecting a threshold value for temperature. In addition, investigators should consider accounting for air pollutants and identifying vulnerable subgroups in their epidemiologic studies.

The recent epidemiologic evidence suggests that PM and O 3 may be confounders, and some studies also found O 3 to be an effect modifier in the warmer months.

In other words, the association between temperature and mortality is partially a result of the effect of PM and O 3. However, this confounding effect is relatively small, and there is clearly an independent effect of both temperature and air pollution on mortality. Others have reported that temperature has a greater effect on mortality with higher levels of O 3 i.

Some of the conflicting evidence for confounding and effect modification by air pollutants may be due to high correlations between pollutants and temperature, making it difficult to tease apart the independent effects of either exposure.

Also, different sources, chemistry, size distribution of particles, compositions and patterns of exposure [ 41 ] of gases and particles are observed throughout the US and elsewhere. Although O 3 generally peaks in the summer throughout the US, for example, particulate matter peaks in the winter in California and in the summer on the East Coast. Thus, there would more likely be an impact of PM on elevated ambient temperature and health outcomes on the East Coast.

Acclimatization may also play a critical role in the temperature-mortality association. People who live in areas where high ambient temperatures or heat waves are typically experienced may be less affected than people who reside in areas where high ambient temperatures are less commonly observed. Thus, even if there is effect modification between ambient temperature and a pollutant, such as O 3 , the influence on mortality may be minimal, but synergistic in areas where heat waves are uncommon.

Several vulnerable subgroups have been identified in the past decade of epidemiologic research, and were often dependent on study location and study population.

Specifically, those dying from cardiovascular, respiratory, and some specific cardiovascular diseases, such as ischemic heart disease, congestive heart failure, and myocardial infarction were at greater risk for heat-related mortality. Infants, young children, and the elderly should be specifically targeted in future studies to prevent heat-related mortality.

With the elderly increasing in urban environments, an important research goal is the identification of clinical patterns of chronic diseases that increase the susceptibility to heat. Furthermore, adverse birth outcomes have been found to be associated with air pollutants in previous studies, but have not been investigated, specifically for ambient temperature.

Although previous studies of air pollution and birth outcomes have not accounted for temperature, some investigators have suggested seasonal associations, implying that temperature could also play a role with adverse birth outcomes and warrants further investigation.

Several biological mechanisms have been postulated for susceptible populations to heat-related mortality, particularly the elderly [ 42 ]. When body temperatures rise, blood flow generally shifts from the vital organs to underneath the skin's surface in an effort to cool down. The body's ability to regulate its temperature also known as thermoregulation may be impeded when too much blood is diverted, putting increased stress on the heart and lungs.

Increased blood viscosity, elevated cholesterol levels associated with higher temperatures, and higher sweating threshold may also trigger heat-related mortality [ 43 ]. The body's ability to adapt to high ambient temperature can be influenced by acclimatization.

People who live in areas where high ambient temperatures are not generally experienced are more likely to be affected by a heat wave. The synergistic impact of high ambient temperature along with high levels of air pollutants, such as O 3 and PM, may also play a role in increasing the mortality effect.

Furthermore, heat waves occurring earlier in the year may have a greater impact on mortality since the population has not had the chance to adapt to hotter temperatures. This review is timely as climate change receives more global attention, and more epidemiologic studies have been recently conducted. It, however, has several limitations.

While it includes the most recent epidemiologic studies using time-series and case-crossover methods, it does not include studies of heat waves or studies using other approaches in an effort to focus on general ambient temperature over longer time periods. Both methods rely on ecologic exposure variables for temperature, and the time-series analysis also uses aggregated counts of mortality. Although the methods used across studies were similar, it was still often difficult to compare estimates between studies because of the analysis type e.

There were also not a sufficient number of studies to conduct a meta-analysis of the results, or other more substantial quantification. Finally, there may be some publication bias in the studies that were chosen, but by using PubMed, the bias may be limited, as it includes most scientific journals.

Further studies need to be conducted in more urban locations so that policies can be implemented for specific areas rather than for an entire geographic area. These studies would be helpful to the National Weather Service, health care institutions, and governmental agencies to implement policies to prevent heat-related mortality and also create a better heat warning system based on current studies. They will also be helpful to establish policy guidelines for the U. Environmental Protection Agency personal communication , and could be used for economic analyses.

Although no formal evaluation of heat-health watch warning systems has been performed to date, some city-based heat-health watch warning systems have already been implemented appear to be successful in greatly reducing mortality following heat waves [ 44 ].

These studies have consisted primarily of time-series and case-crossover studies, and were summarized this review. Several vulnerable subgroups have been identified, including those dying from cardiovascular, respiratory, and some specific cardiovascular diseases, such as ischemic heart disease, congestive heart failure, and myocardial infarction.

Thus, infants, young children, and the elderly should be specifically targeted in future studies to prevent heat-related mortality. Many of these outcomes and vulnerable subgroups have only been identified in recent epidemiologic studies of ambient temperature and were dependent on the location and study population.

Basu R, Samet JM: Relation between elevated ambient temperature and mortality: a review of the epidemiologic evidence. Epidemiol Rev. Article Google Scholar. Int J Biometeorol.

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