Weather, Climate, and Human Health
To appreciate the major impact weather can have on our daily lives, one need only consider 1999. Early in the year, the worst dry spell on record scourged much of the east coast of the United States. Later in the year, some areas of the country-including parts of the drought-ravaged east coast-experienced the opposite end of the weather spectrum: heavy rains and record flooding. Frequent media reports throughout the year have focused on the plight of American farmers, county water departments, or insurance companies struggling with drought, floods, and other consequences of inclement weather.
More Than a FeelingAlthough most of us realize on a very personal level that weather affects the way we feel, a growing body of scientific evidence is confirming this hunch. Increasingly, researchers are using weather and climate predictions as a compass to track health trends and develop preventive measures. Using principles of epidemiology, meteorology, and physiology, they are examining the influence of weather and climate on health. The objectives of this fairly new science of "biometeorology" 2,3 are threefold. First, on a very large scale, biometeorologists look at the relationship between atmospheric patterns around the world, changes in climate, and effects on health patterns. Second, they examine, on a smaller scale, the effects of weather patterns on localities. Third, they track how weather affects individual health.
What We Know NowFrom a global perspective, there is good cause to contemplate the relationship between health and weather. Indeed, a number of nations, recognizing the potentially huge impact of global climate changes on human health, designated the 1990s as the "International Decade for Natural Disaster Reduction." This action recognized that some populations are more vulnerable than others to the consequences of weather and climate.2,4 While many suspected links between meteorologic occurrences and human health await scientific confirmation, some linkages are already fairly well defined. For example:
If climate changes do cause more frequent, more intense weather extremes, more and better weather data will be necessary for response planning and education. For localities, planning for weather- and climate-related challenges is essential and will become even more so over the next decades. Especially in northern cities such as Pittsburgh, Detroit, Chicago, and New York, climate-related mortality is high. Research estimates indicate that 20% of humans are "weather sensitive," or particularly prone to the ill effects of weather extremes, with the elderly being disproportionately stressed. 3 Additionally, climate changes lead to population migration, causing changes in societal composition, economic profiles, and employment pools. The repercussions of weather for individuals go beyond merely feeling "blue" on rainy or overcast days or the ability (real or perceived) to predict storms on the basis of joint pain. Although many weather-related health afflictions are common coffee-break topics, considerable information about subtle effects of weather and climate is emerging.
Weather vs. ClimateMany people may not realize that the terms "weather" and "climate" are not interchangeable. Climate refers to the weather pattern over a long period of time in a specific area; weather is the actual state of affairs outside the window at a given point in time. Climate suppresses or expands the range of many diseases, and weather contributes to the timing and intensity of disease outbreaks. Thus, in the context of disease, climate provides motive, and weather provides opportunity. 7Certain weather phenomena have global effects we are only now starting to understand. One such phenomenon is "El Niņo," or, more accurately, the "El Niņo Southern Oscillation" (ENSO). This weather phenomenon produces periodic short-term weather changes once every five years on average. 4 ENSO emanates from the Pacific Ocean and was named by Peruvian and Ecuadoran fisherman who noticed periodic changes in their catch of anchovies, which are very sensitive to water temperature changes. As the seas warmed, the anchovy catch would decline. Fisherman noticed that the warming effect peaked around Christmas, thus their choice of the term "El Niņo," Spanish for "the Christ Child." Specifically, it is a change in prevailing winds, resulting in unusually warm sea water. Sea surface temperature (SST) increases and, with atmospheric interaction, causes changes in movement of air masses and associated cold or warm fronts. ENSO also includes an opposite phenomenon, "La Niņa," which causes a decrease in SST and a similar stream of weather changes. Each El Niņo has unique features and can result in drought (and, consequently, food shortages and famine). In some areas, drought is twice as likely to occur in El Niņo years. 4
Pieces of a Global PuzzleThe "greenhouse effect" is expected to change climate (not weather). The greenhouse effect describes a situation where gases (primarily carbon monoxide) are trapped in the upper atmosphere, and long-wave radiation increases, boosting atmospheric temperature around the earth. This is a measurable effect. Scientists estimate that carbon monoxide concentrations were approximately 280 ppm in 1800, but are now 340 ppm. By the year 2100, they estimate, concentrations could rise to as much as 2240 ppm if actions to decrease greenhouse gas emissions are not taken soon and sustained. The outcome of increased greenhouse effect is startling: Atmospheric temperature could increase between 1.5oC and 4.5oC by 2100, resulting in sea levels 41-68 cm higher than today. Additionally, a small change in temperature can cause huge changes in food production. Using the above temperature projections, scientist predict that the number of people worldwide who will be hungry will double by 2060. 8
The "butterfly effect" also complicates weather and climate. This effect was described by Belgian Nobel Laureate Ilya Prigogine as part of his work on chaos theory. He heightened our awareness that under some circumstances, a seemingly inconsequential event such as the movement of a butterfly or group of butterflies might change weather in significant and unpredictable ways.12 Just as in the fields of pharmacy or medicine, the process of collecting raw data, interpreting its meaning, and delivering findings to its ultimate user is complicated in biometeorology. On a large scale, biometeorologists use satellite and sophisticated computer models (called general circulation models) to track weather patterns around the world. Ocean temperatures can be read by satellite. The atmosphere behaves as a fluid, and the laws of fluid dynamics can be applied. Doppler radar is also used to locate precipitation, determine its intensity, and define its direction and rotation (if present, as in a tornado). Just as medical researchers require absolute measures when gathering data, biometeorologists look at temperature, humidity, number of sunshine hours, wind speed, precipitation, and geomagnetic activity. In addition, they look at the rate of change of each of these factors.3 Biomedical researchers sometimes find that an abnormal lab value doesn't necessarily manifest itself as a changed clinical picture. Similarly, biometeorologists have found that there is sometimes no substitute for human "ground spotters." These weather diagnosticians observe local weather and fine-tune information through visual confirmation and direct observation of storms, tornadoes, or wind direction.
Weather Events and Health EffectsIt's already well established that during periods of stormy weather, localities and individuals-including long-term care populations-are challenged by a number of factors. Storms, which include heavy rains, snow, or winds, cause tremendous damage on the local level and hardship for long-term care facilities and residents. Obvious complications include accidental injury,9,13 which requires greater emergency and disaster readiness by staff. Most certifying and accrediting bodies require a certain level of preparedness in long-term care facilities, and pharmacists are essential members of the team that develops the facility's plan.Considerations in the long-term care facility should include how to maintain infection control procedures if the water supply fails, and how to safeguard food, medication, and supplies that require refrigeration if electricity fails. Many facilities are reviewing their emergency preparedness procedures as part of efforts to prevent "Year 2000" computer glitches. While Y2K readiness exercises have been time-consuming and meticulous, they will help not only as a preventive measure for any Y2K failures, but also help to improve disaster plans. Flu Outbreaks. Weather and climate can make or break a flu season. Shortly after the first frost, the first few cases of flu will develop. There is good evidence that flu outbreaks are more serious in cold and very cold weather conditions. In the winter of 1996-97 (a very cold winter), statisticians estimate that 49,000 more deaths occurred than expected. These are termed "excess deaths"; they are not connected with heat, cold, or accident caused directly by the weather (For example, a cardiac arrest while shoveling snow is weather-related and thus not an excess death). Many of these excess deaths were due to influenza, which peaked in December and January and coincided with the coldest temperatures.14 As a pulmonary infection, influenza begins as air circulation decreases pursuant to closing windows and turning on the heat. Once the heat is on, warmer, drier air predisposes residents to dry mucous membranes and a greater chance of infection. Early and thorough promotion of vaccination can help. Allergies and asthma. People who have asthma or allergies are also at the mercy of the weather from time to time. Thunderstorms can precipitate breathing difficulties in two ways. First, windy conditions that usually precede storms stir dust, mold, and pollen; this can activate allergies. Second, heavy rains tend to break pollen into smaller pieces, allowing the fragments to be inhaled deeper into the lungs and causing more debilitating symptoms.13 For residents with asthma, exposure to air pollution that is either endogenous to the area or a transient effect of a weather-induced fire increases shortness of breath. This can be severe.7,15 Additionally, dry and cold air is hazardous to asthmatics. It can impair breathing, possibly by causing vasoconstriction and reactive hyperemia.5 Residents with allergy may have more symptoms under several other weather conditions. Wind and heavy rain are addressed above. Falling barometric pressure can also precipitate allergies. Whenever weather conditions have the potential to aggravate asthma or allergies, closing windows and using air conditioning or filtration systems, if appropriate, can decrease exposure to allergens. During days when pollen counts are high, showering at bedtime will help residents wash away any pollen accumulated during the day and promote sleep. Breathing warmer, slightly humid air will help asthmatics on cold days.13 Use of p.r.n. decongestants or antihistamines may also help. Nursing staff may notice that many residents develop runny noses when the weather becomes cold. Called "cold air rhinitis," it can be treated with aerosol ipratropium bromide if it is troublesome or persists.13 Validating an old wive's tale. All of us know people who claim to be able to predict weather changes with their joints. There is some evidence to suggest that this purported ability is, indeed, in their joints and not in their heads. Several small studies have confirmed that for people with rheumatoid arthritis or osteoarthritis, pain increases when barometric pressure changes or when temperature or humidity are increasing.5,9,16 Further, people who have osteoarthritis tend to feel more pain on rainy days, and people with fibromyalgia are also sensitive to barometric changes. This tendency to feel pain may be more pronounced in women than in men.16 The key word here is change; changes in temperature or barometric pressure induce discomfort. Once the pressure or temperature has stabilized, discomfort does, too.9 In many older people, any weather front, change in barometric pressure, or blast of cold air can cause pain.10 Those who suffer from Raynaud's disease react to cold. They experience a peripheral triphasic color change as small arteries and arterioles constrict. Initially, their skin blanches as ischemia sets in. Next, tissue becomes blue in response to cyanosis. Finally, hyperemia manifests itself as redness. Residents may describe pain or parasthesis in the final stages. 5,9 The best strategy is to avoid extreme cold.
Weather Effects on Body SystemsIn addition to the weather-related phenomena discussed above, research suggests that meteorologic events can significantly influence a variety of bodily functions, including blood circulation, cardioregulation, cancer risk and incidence, immunoregulation, and ability to fight infection.Circulation and cardioregulation. Both the circulatory and the cardiac systems can be significantly stressed by extremes of temperature. Approximately half of excess deaths in extreme weather are caused by coronary events or cerebral thrombosis.5,18 Additionally, as temperature drops, the incidence of coronary events and cerebral thrombosis begins to increase within 24 hours.5 The reason for this trend is not clear. Scientists do know that the normal physiological response to cold includes a rapid change in many blood components. Those considered most important to circulation and coronary health are decreased total blood volume (leading to reduced oxygen supply10), increased fibrinogen (promoting coagulation), and increased blood viscosity and cholesterol levels (promoting arteriosclerosis17). It comes as no surprise that coronary events such as angina and myocardial infarction peak during autumn and winter,3,8,18 and circulatory ailments peak in January and February. 8,18 Extremes of temperature are not the only weather factors that can contribute to cardiovascular decline. Ten percent of lightning fatalities are cardiovascular in nature, possibly due to altered cardiac electrical conduction.13 Neoplastic disease. Some cancers have clear and readily understood patterns. For example, the incidence of malignant melanoma is higher in areas where the number of sunlight hours is highest.13 Cervical and lung cancer may occur more frequently in warmer climates, and digestive track malignancies seem to occur more often in colder climates,10 possibly because of reduced availability of fresh fruits and vegetables in winter months. There is a seasonal fluctuation in detection of human papilloma virus and cervical cancer (which are related).19,20 The peak incidence of newly diagnosed uterine cervical cancer cases occurs in February.20 No clear causative factor has been identified. Immunoregulation. Immune response varies during the year, and weather or climate can influence the incidence of infection. Some researchers believe that biometeorological situations alter social structure, ecological balance, and global patterns (See box above). Most people experience increased circulating leukocytes in August and December, thus experiencing better immunity to infection.10 However, levels of T-helper cells are lowest in April and October, increasing vulnerability.21 That said, preventive measures such as hand washing and avoiding contact could be promoted in March and September to help prevent the spread of disease. Infectious disease. Weather itself affects the type and spread of infectious disease, especially vector-borne disease. Biometeorologists are able to predict the type and severity of malaria infections on the African continent up to five months in advance, making preventive measures a more likely success.2 Predictions of other diseases including encephalitis and cholera can also be made fairly accurately. While these diseases rarely occur in the United States, there have been isolated cases, and the risk of transmittal increases as travel becomes easier. For example, New York city experienced an outbreak of possible Nile Fever beginning in August of this year. Experts suspect that this serious fever was transmitted by an infected mosquito from another country. More than 30 people have been infected, with the very young and the very old at highest risk. Symptoms include fever, malaise, headache, and encephalitis, possibly leading to death.22 Scientists warn that vector-borne diseases are radiating from their endogenous localities at increasing rates.8 Two vector-borne diseases of importance in the United States are tick-borne diseases and hantavirus.2,7,13 Mild winters in particular will increase the tick population, causing the spread of Lyme disease.13 Hantavirus, which is carried by rodents in the southwestern part of the country, increases considerably when weather conditions favor rodent proliferation. Heavy rains after periods of drought favor rodents and have set the stage for serious outbreaks of hantavirus pulmonary syndrome in the United States recently.7 Any natural disaster that involves water creates a nightmare for infection control officers. Disruption of water and sewer service increases the chance of infectious outbreaks in two ways: Normal sanitation measures cannot be employed, and raw sewage or dirty water carry infectious agents. After a flood, leptospirosis is often a problem.2 During a humidity or heat wave, fungal infections can be aggressive.13 Ensuring the availability of adequate supplies of potable water, waterless hand cleaner, or alternative cleaning agents is important.
Weather and MoodNeurologists and psychiatrists also report climate- and weather-related conditions. For example, multiple sclerosis is common in the higher latitudes but rarely occurs in equatorial regions. Researchers believe that a vitamin deficiency may have some relationship to this pattern, but no firm cause has been established.10 Monosymptomatic neuritis peaks in the spring and ebbs in the winter. Again, no cause has been identified.23On a broader scale, many people report weather-induced headache or a seasonal pattern of headache occurrence. As barometric pressure falls, headaches are more likely to occur. Use of p.r.n. medication may be needed if this is the case, and elimination of other potential headache triggers such as alcoholic beverages, chocolate, monosodium glutamate, or stress may alleviate symptoms.10,13 Mental health specialists are usually in demand after a natural disaster occurs. Post-traumatic stress disorder, depression, insomnia, substance abuse, and violence increase. Temporary symptoms are more common, though symptoms can continue for years. Although researchers once believed that suicide rates increased after floods, hurricanes, or earthquakes, results of recent controlled studies do not support this hypothesis. Studies do indicate, however, that serious mental health problems are more prevalent after disasters. These problems are certainly predictable; death or injury of loved ones, destruction or loss of property, and financial instability can cause or contribute to mental illness.24 Residents confined to long-term care facilities may experience understandable anxiety about family members and friends who are affected by a natural disaster. Agitation and aggression increase with temperature changes, especially increases to temperatures greater than 90oF. Widespread use of air conditioning has helped, but long-term care facilities that experience temporary power outages should anticipate more agitation among residents and reduce other potential triggers while awaiting restoration of service. Windy conditions have also been proven to contribute to agitation, irritability, anxiety, apathy, and depression.3 Seasonal affective disorder (SAD), first described in 1982, is no longer subject to skepticism. Researchers believe that melatonin production increases in winter, leading to an increased urge to sleep or reduced desire to interact with others.3,13,25 Melatonin levels generally decrease with age, but the elderly do experience seasonal shifts, and SAD may worsen with age.26 Natural or synthetic sunlight suppresses melatonin production, thus improving mental health. Early-morning exposure to light appears to be better than exposure late in the day.25
Directions for Future ResearchDespite its lack of predictability, we know more about global climate changes than global health. Development of a health care monitoring system similar to the global climate and weather monitoring system may occur as communication becomes easier. It will help us understand how small changes in one locale may cascade into international health crises. Like climate and weather systems, health systems must look at dynamic models and consider more factors than ever before.6 In this way, we may someday be able to predict all types of health information in much the same ways as weather is predicted today.Until then, we will have to continue to assess the health effects of ENSO, the greenhouse and butterfly effects, and all weather phenomena, and continue to look for even better cause-and-effect data. Through practical adjustments to our environments and approaches and reliance on modern amenities, we may be able to eliminate weather-induced suffering at the level of the individual, lessen the impact and improve disaster response on the level of localities, and reduce mortality on a global level.
References
Additional references available upon request.
American Society of Consultant Pharmacists. |
In 1897, the editor and essayist Charles Dudley Warner observed, "Everybody talks about the weather, but no one does anything about it." 1 More than a century later, weather remains a major topic of daily discussion, but increasingly, scientists are trying to use weather and climate data to project disease patterns and formulate action steps to prevent or minimize the adverse effects on human health.