‘Climate change negatively affects birth weight’

Chemicals in packaging, antidepressants, hormones in food are
causing modern humans to gain more weight, scientists claim

FROM melting glaciers to increasing wildfires, the consequences of climate change and strategies to mitigate such consequences are often a hotly debated topic.

A new study led by the University of Utah, (UU) United States, adds to the ever-growing list of negative impacts climate change can have on humans—low birth weight.

The first of its kind, the two-year project led by UU geography professor Kathryn Grace examined the relationship among precipitation, temperature and birth weight in 19 African countries. Grace and her team utilized high quality, detailed climate data in conjunction with extensive health data to focus on climate change and its effects on birth weight in the developing world.

The new findings show that a pregnant woman’s exposure to reduced precipitation and an increased number of very hot days indeed results in lower birth weight.

“Our findings demonstrate that in the very early stages of intra-uterine development, climate change has the potential to significantly impact birth outcomes. While the severity of that impact depends on where the pregnant woman lives, in this case the developing world, we can see the potential for similar outcomes everywhere,” said Grace.

The other authors are Frank Davenport, Heidi Hanson, Christopher Funk and Shraddhanand Shukla. The team reported the findings in Global Environmental Change.

Christopher Funk (US Geological Survey) and UC Santa Barbara Climate Hazards Group provided the climate data used in the study, and have just detailed exceptional East African rainfall declines in a new paper in Nature Scientific Data.

Meanwhile, a recent study revealed people were 10 per cent heavier in 2008 than in 1971, despite eating the same calories.

And they were around five per cent heavier in 2006 compared with 1988, despite doing the same amount of exercise.

Now, the authors of the study have explained they believe there are factors beyond calorie intake and exercise that are causing today’s millenials to gain more weight.

Professor Jennifer Kuk, from York University, Toronto, told the Atlantic that increased exposure to chemicals and pesticides; anti-depressant use and a change in our gut bacteria are three key reasons why people today might be fatter despite similar diets.

Pesticides and chemicals in food packaging may be altering our hormones, which affects the way our bodies gain weight. Antidepressant use has also soared since the 1970s, she said.

For up to a quarter of people, antidepressants including the selective serotonin reuptake inhibitor (SSRI) drugs, ‘blockbuster’ pills in the US, cause weight gain.

In the United States (US), antidepressants are the third most commonly prescribed drug.

In the United Kingdom (UK), the number of antidepressant prescriptions has increased more than twofold between 1975 to 1998, according to the Journal of Public Health.

Finally, Professor Kuk told Atlantic journalists that people’s ‘microbiomes’, their gut bacteria, may have changed in the last 35 years.

More meat and animal products contain hormones and antibiotics that promote growth.

Over time, constant exposure to these may change a person’s microbiome and cause them to pile on the pounds more easily.

Artificial sweeteners used to flavour food may also play a role, as it may cause insulin resistance.

Insulin is the hormone that breaks down sugar into energy, and if the body becomes resistant to it, excess glucose circulates in the bloodstream.

The excess sugar remains in the bloodstream, which is sent to the liver, where it is converted into fat.

In the study, she said other affect our body weight, including genetics, timing of food intake, stress, and even night-time light exposure.

“There’s a huge weight bias against people with obesity,” Kuk told the Atlantic.

“They’re judged as lazy and self-indulgent. That’s really not the case. If our research is correct, you need to eat even less and exercise even more just to be same weight as your parents were at your age.”

Weight management is actually ‘much more complex than just “energy in” versus “energy out”, she concluded, in a statement on the study, published in the journal Obesity Research & Clinical Practice.

“That’s similar to saying your investment account balance is simply your deposits subtracting your withdrawals and not accounting for all the other things that affect your balance like stock market fluctuations, bank fees or currency exchange rates.”

“Ultimately, maintaining a healthy body weight is now more challenging than ever,” she said.
Impacts of low birth weight are far-reaching

With the inaccuracy of determining exactly when a pregnancy began in rural countries which lack pregnancy tests and the inability to measure characteristics like a newborn’s cognitive development, low birth weight is the most reliable measure of whether a pregnancy has been negatively affected by an external factor.

Low birth weight is defined by the World Health Organization (WHO) as any baby born under 2,500 grammes.

Low birth weight infants are more susceptible to illness, face a higher risk of mortality, are more likely to develop disabilities and are less likely to attain the same level of education and income as an infant born within a healthy weight range.

Consequently, the financial burden of a low birth weight infant can be significant. The costs of newborn intensive care unit stays and services, re-hospitalization and long-term morbidity can add up quickly, and in developing countries where such support services are less common and physical disability is considered a social stigma, low birth weight can be particularly impactful.

The first continent-wide analysis
In 2013, Grace and colleagues combined health data from Demographic and Health Surveys, which is funded by the United States Agency for International Development to collect and disseminate data on health and population in developing countries, and growing season data, with temperature and rainfall data from a variety of sources.

The team collected growing and livelihood zone information from the U.S. Agency for International Development’s Famine Early Warning System programme and precipitation data from the Climate Hazards Group InfraRed Precipitation with Station data set.

In total, the team examined nearly 70,000 births in 19 African countries between 1986 and 2010 and matched these births with seasonal rainfall and air temperatures, as well as variables describing the mother and mother’s household, such as education level and whether the household had access to electricity.

This is the first time researchers utilized fine-resolution precipitation and temperature data alongside birth data to analyze how weather impacts birth weight.

To generate precipitation records for each birth, the team calculated the average precipitation for a given month within 10 km of the child’s birth location. This was done for each month up to one year prior to each child’s birth. The values were then summed over each trimester.

The same method was used to generate temperature records for each birth. The team first calculated the maximum daily temperature for a given calendar day within 10 km of a child’s birth location. From there, the number of days in each birth month where the temperature exceeded 105 F and 100 F as the maximum daily temperature were summed over trimesters.

Evidence and impact of climate change
The results show that an increase of hot days above 100 F during any trimester corresponds to a decrease in birth weight. In fact, just one extra day with a temperature above 100 F in the second trimester corresponded to a 0.9 g weight decrease; this result held with a larger effect when the temperature threshold was increased to 105 F.

Conversely, higher amounts of precipitation during any trimester resulted in larger birth weights. On average, a 10 mm increase in precipitation during a particular trimester corresponds to an approximate increase in birth weight of around 0.3 to 0.5 g.

“While the results are dependent on trimester and location, the data shows that climate change—a combination of increased hot days and decreased precipitation—correlate to lower birth weights,” said Grace.