Why we get sicker when the weather changes

Weather and environmental stress affect our health. From psychological effects to migraines, joint pains and increased heart disease risk factors, it has been known for decades that climate plays a role in overall health status including death rates.

Data collected in Washington D.C. from 1987 to 1989 that analyzed death rates from 89 major counties in the U.S. found warmer climates had reduced death rates. Peak death rates were in the winter months with lowest mortality in the summer.

{mosads}This study identified that it was temperature, not increased sunlight, which reduced deaths. Further studies performed in Germany in 1998 found that colder weather posed a significant risk factor for increased death rates.

More current studies have further demonstrated the link between climate and risk for chronic health conditions. For instance, for individuals with heart disease, cold climates can create a significant hazard.

As the temperature drops, blood vessels narrow and can raise the risk of a heart attack. The risk for a heart attack is further compounded by intense physical activity, like shoveling, in cold temperatures. These activities can increase the workload on the heart while decreasing the blood supply to the coronary vessels.

Cold weather has also been implicated as an asthma trigger because cooling of the airway can trigger swelling of tissues.

While there’s no clear evidence that chilly weather promotes the common cold, quick and significant weather changes are found to impact the immune system, and viruses associated with the cold and flu are believed to be more easily transmitted in cold weather.

Another surprising weather related phenomenon occurs with thunderstorms and asthma epidemics. Dr. Gennaro D’Amato, who has researched this area extensively, says that the association between thunderstorms and asthma are related to the fact that storms can cause pollen to become concentrated and released into the air after the thunder and osmotic shock. This is particularly dramatic during the first 20-30 minutes of the storm. These conditions could also explain why allergy sufferers have more symptoms after heavy periods of rain.

Conversely, extremely hot weather and high humidity can have health ramifications. Excessive sweating can cause heat stroke and dehydration which can be a serious health concern for older individuals and people with kidney or heart disease. Hot temperatures combined with high humidity and air pollution can also result in difficulty breathing, especially for those with chronic lung conditions.  

Other studies have shown a link between violence and extreme heat. Violent crime has been associated with warmer weather with dramatic decreases in the winter months.

Weather stability seems to be a factor in migraine triggers and joint pain. When the humidity increases dramatically, the barometric pressure decreases, or an acute drop in temperature occurs, this may result in more migraine or joint pain symptoms in individuals with these conditions.

While more research is needed to clearly demonstrate the cause and effect relationships between mental health and weather, there are well established links between seasonal factors and the incidence of suicide. Some studies have shown that better-than-expected weather — that is, warmer winters and cooler summers — may be connected with increased happiness, less stress and enhanced wellness.

Currently, links between weather, mood and cognition are starting to emerge. In one study, better weather was related to better memory, positive mood, and cognition as more time could be spent outside in the spring.

There is also emerging research and evidence for seasonal affective disorder (SAD) which can affect mood due to lack of sunlight in winter months.

No discussion of weather and health is complete without referencing the impact that climate change will continue to have on global health as well as current, emerging and future health threats, especially to the most vulnerable populations.

From natural disasters like hurricanes, wildfires and earthquakes to people-causing activities like air pollution to insects and other vectors that carry and transmit disease, the weather and climate will continue to significantly affect our overall health.

Kristin Mascotti, M.D., is the Quality Medical Officer at Long Beach Memorial Medical Center and Miller Children’s & Women’s Hospital Long Beach