Climate Change and Global Health

Storm Surge Flooding, Westport, Washington, November 2009

Climate Change and Global Health

Climate change poses a number of risks to global health.  These risks draw our attention to the fact that health issues operate on a scale that transcends our own individual concerns, extending well beyond local communities, state and national boundaries.  

I attended a lecture in February, 2011, by Dr Howard Frumkin, Dean of the University of Washington School of Public Health on the health risks of climate change.  It was an interesting talk, covering many areas where climate change impacts global health. These impacts may be associated with the increased frequency of extreme weather events. 

Extreme weather events discussed included increased heat, cold, melting, freezing, flooding and droughts.  Increased atmospheric instability may give rise to more frequent hurricanes and tornadoes. Extreme weather events can be viewed on various time scales, from 50 to 100 year storms, to events on a more geological time scale.

Heat stress is of particular concern to the elderly, the young and the immune-compromised. Extreme heat, especially in non or inadequately air-conditioned spaces may result in premature mortality during heat waves, in the vulnerable, especially in the city where paved areas draw heat.  Dr Frumkin was concerned about the "harvesting" effect of heat waves on elderly, urban, populations.

Cold, snow, ice and freezing also may become survivability issues, involving issues of heating and interruption of water and electrical service.  Storms may impact travel and thus food supply, transportation of vital supplies to population centers and medical facilities.  

Public health challenges may emerge with air or water quality issues, impacting respiratory, cardiovascular, and other associated systems.  Infectious diseases may spread via the air or water through vectors  such as tic or mosquitoes, or via zoonotic means through human to animal or animal to human spread).  Allergies may develop in response to climate changes, and new pathogens may emerge or spread to different areas.

Air pollution is a problem which affects more than just urban areas.  With experience working in the regulatory air quality sector, I realize the widespread impacts that pollutants such as ozone and other pollutants have.  Photochemical reactions involving products of combustion (e.g. auto exhaust) take place in the atmosphere resulting in ozone levels downwind of major urban areas. As the reactions involve sunlight and heat, the levels on sunny and hot days increase in the summer. In the fall and spring periods of extended air stagnation resulting from stalled high pressure weather systems may increase the respiratory and cardiovascular burden on the vulnerable patient group. Air pollution does not know boundaries, thus residential and industrial pollution from other countries may impact us, as ours impacts theirs.  Forest fires add to the impact.  Extreme weather may impact all these issues.

The impact of climate change, extreme weather events and public health challenges may impact food production, may result in civil conflict, dislocation of impacted people and may increase the expression of mental health issues .

The discussion of climate science drives the discussion on public health impacts as projections are made regarding the manner in which changes will take place in Earth's climate systems.  Modeling climate systems drives downstream weather and public health challenges. These challenges are studied in a variety of settings, including federal government institutions such as NOAA, NASA and the CDC, and at a variety of state and local governmental and, at private institutions.  The Intergovernmental Panel of Climate Change and the National Climate Assessment have comprehensive plans reflecting policy in this area.

Extreme weather events can result in significant mortality and morbidity, as well as impacts to property.  Tornadoes and Hurricanes and wind storms may result in death and injuries from flying objects, falling trees and power lines as well as medical emergencies secondary to the event.  Fires may result from damaged gas lines. 

Increased flooding and storm surge may result in drownings and damage to property. Flooding may increased the spread of infectious diseases, problems with sewage systems and interruptions in drinking supplies

Drought may bring about reductions in food supply.  This is a serious issue as crops may be challenged to grow in areas where they were previously able to.  Vegetation, vectors and pathogens may spread into other areas as a result of warming.  This impacts the latitude at which such impacts occur as well as the altitude above sea level, moving to cooler latitudes and elevations.

More weeds may develop in urban areas in response to climate change and global warming as vegetation adjusts to the changing environment.

Extreme weather events thus may have public health impacts relating to many systems, resulting in dislocation of people and mental health issues as citizens adjust to the events.

The challenge is how to address climate change issues in the context of these public health issues.

Leptin

Butter

I attended a lecture in 2008 about leptin signaling given at Harborview Medical Center through their research programs on diabetes, metabolism and obesity.  The lecture, although highly technical, was  interesting and it gave me plenty to think and read about.

Leptin is what is called a signal transducer.  A signal transducer is an extracellular  signaling molecule that activates a receptor inside or on the cell surface, initiating a series of events, biochemical reactions.    Leptin signaling is involved in a number of areas relating to the management of energy throughout the body, regulating or giving permission for the use of energy for a variety of vital functions.  As I read more about leptin, it led me into a labyrinth of other, associated issues.

Leptin is involved in signaling relating to mesolimbic (dopaminergic) reward centers, food, satisfaction, glycemic control, saiety and reproduction.  Leptin deals with long term energy storage, provision of energy to the brain and gives permission for the use of energy falling within its defined duties.  Intuitively, one wonders what happens if energy demands are requested for things that aren't associated with its associated duties.

Leptin acts to communicate to the Central Nervous System the availability of energy stores.  It acts to restrain food intake and induce energy expenditure, when necessary.   Leptin acts with other systems, such as the Sympathetic Nervous System,  and with factors such as thyroid hormone  and insulin,  in regulating energy use throughout the body and in insuring the thermodynamic  efficiency of skeletal muscle, for example.  Leptin is also involved involved in the cardiovascular system, for example in cardiac hypertrophy.

Leptin is increased, or up-regulated, in obese people.  It increases appetite, generates a low metabolic rate, decreases thyroid function and is impacted by sleep apnea  issues.  Dysregulation of leptin adversely impacts fertility.  Leptin acts on lipid and glucose metabolism.  Leptin also regulates bone metabolism.  This may serve to improve structure with increasing weight by regulating the allocation of higher density bone development.    Leptin resistance occurs during obesity when increasing leptin levels do not have an impact.

Leptin acts in the brain in a neuroprotective  fashion that may also impact memory.  Leptin may be necessary to protect the cell against cell death (apoptosis).

Leptin plays a key role in thermoregulation, working through diverse systems such as the brain's preoptic area and hypothalamus.  Studies in the brown adipose tissue (BAT)  of mice injected by virus indicated involvement of leptin in regulating BAT circuits.  Severely obese mice that lack leptin or its receptor show decreased BAT thermogenesis, and are thus challenged to maintain their body temperature and adapt to cold temperatures.

Leptin may be a key component in considering survival issues under a variety of scenarios or projections associated with climate change modeling.  It may react to a variety of seasonal (zeitgeber) cues, as well as sexual cues regarding melatonin , odor and reproduction.  It will react to hedonistic feelings regarding food, appetite and to the allocation of resources regarding shorter term versus longer term energy needs.

Leptin plays its role along with a host of other players in this complicated web of life.