Providing mothers and their young children with access to sanitation and good hygiene reduces stress and may prevent illness later in life, according to a new US study.

The study, published in Nature, analysed 5,551 pregnant women and their children in rural Bangladesh. It provides the clearest indication yet that environmental factors such as sanitation can have an impact on long-term health via what is known as epigenetic programming — where external conditions cause lasting damage to DNA and make children vulnerable to a range of acute and chronic conditions.

Participants in the study were placed into one of seven groups, four of whom received nutrient supplements and then one of the following: clean drinking water, sanitation, handwashing stations or nutrition counselling. The fifth group received water, sanitation and handwashing interventions while the sixth received water, sanitation, handwashing and nutrition interventions. The final group received no interventions.

The results showed the children whose mothers received drinking water, sanitation, handwashing and nutrition had greater regulation of the physiological stress system in early childhood. 

“A regulated stress response is essential for healthy child growth and development trajectories,” the study authors said. 

“Chronic stress… may cause irreversible harm if it occurs during the early years of life (under age 2 years), [which is] a period of rapid growth and development.”

The trial, which began in 2009, found that a combined nutrition, water, sanitation, and handwashing intervention reduced oxidative stress. Oxidative stress, the accumulation of unstable free radicals that damage DNA and cellular structures, has been implicated in the pathophysiology of several paediatric disorders including asthma.

This sort of damage to DNA has also been linked to diseases such as cancer, lupus, muscular dystrophy and birth defects. Researchers claim this new study, which is the first of its type to be conducted outside the first world, provides the most accurate evidence yet on the way environmental factors such as sanitation and hygiene influence early childhood development and health.

Audrie Lin, one of the study’s authors, lived in Bangladesh and Kenya for six years to help set up the trial and train teams on the ground.

“This is really representative of the conditions that a majority of the world’s population contends with,” Lin said.

”When this type of research is done in high-income countries, you’re not really capturing all of these important stressors that could affect a child.”

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