The risk of developing food allergy in premature or low birth-weight children.

Researchers know that children born pre-maturely or children born very small, have an immature immune system and immature digestive system.  Despite this, their immune system is able to respond to some things “normally”, for example, vaccines.  Researchers have many questions about how pre-mature and low birth weight infants respond when exposed to food allergens. 

Some researchers have assumed that children born with immature immune and digestive systems are more prone to developing food allergies.

Our Research Question:  Are children born pre-maturely or born with low birth weight more at risk of developing food allergies compared to normal-birth-weight children?

SAGE researchers looked at the health records of all children born in Manitoba in 1995.  Children were divided into groups based on * gestational age and * weight at birth.

Researchers then looked at the number of children in each group that had food allergies. Children who had had a hospital or emergency room admission for food allergy or a prescription for an Epinephrine auto-injector (Epipen or Twinject) before the age of 7 were considered food allergic.

*Gestational age refers to how far along the mother was in her pregnancy at the time of birth (30 weeks, 35 weeks, 40 weeks).  Children born at 37 weeks or less were considered pre-mature.

* Low birth weight refers to children who weigh less than 2500 grams at birth

Findings:

Almost 14 000 children were born in Manitoba in 1995. 

6.3% were born prematurely

4.9 % were born with a low birth weight 

2.06% of the premature/low birth weight children had food allergy by the time they were 7 years old.

The rate of food allergy in the premature/low birth weight group was the same as the rate of food allergy in normal children.

Many doctors have suggested to parents of pre-mature and low birth weigh babies not feed them solids before 6 months of age, milk or eggs before 1 year and peanuts and fish before age 3, believing that this would help prevent the development of food allergies. 

In this study, pre-mature children who ate these food before the recommended age did not have a higher rate of food allergy.

Risk factors for developing food allergy were: having a mother with asthma or food allergies, having a higher income and being a boy.

Conclusion:

Pre-maturity and low birth weight did not increase a child’s risk of developing food allergy. 

Delaying certain foods until a certain age did not decrease the risk of  developing food allergy. More research needs to be done to see if delaying certain foods until later in life increases or decreases the risk of food allergy.

The risk of developing food allergy in premature or low birth-weight children.

Liem JJ, Kozyrskyj AL, Huq SI, Becker AB. J Allergy Clin Immunol. 2007 May;119(5):1203-9. Epub 2007 Mar 26

Depression is more common in girls with non-allergic asthma.

Chronic illnesses increase the risk of depression and anxiety in children and teens.  Children and teens with asthma often suffer from hayfever, food allergies or eczema as well as asthma.  These illnesses affect the child’s quality of life and have been linked to depression.

Depression and anxiety disorders are twice as common in children and teens with asthma. Previous studies have shown that 16.3% of children and teens with asthma have some symptoms of depression or anxiety compared to 8.6 % of children or teens without asthma. 

Obesity rates are higher in children with asthma.  Obesity has also been linked to lower self esteem and depression.

Researchers wanted to know more about the relationship between asthma and depression.

Our Research Questions:

• Are children and teens with asthma at increased risk for depression?
• Is there a difference between having allergic asthma or non-allergic asthma when it comes to depressive symptoms?
• How does the child or teen’s weight affect the risk of depression with asthma?
• What is the relationship between allergic symptoms, asthma and depression?

 Research Findings:

• 431 SAGE study children were seen at 11-14 years of age.
• 1/3 of all children with asthma had some symptoms of depression or anxiety.
• ½ of all children with non-allergic asthma had symptoms of depression or anxiety.

 Depressive symptoms were more frequently seen in girls, in First Nations children, and in children who were overweight.

Boys:  Having allergic asthma or non-allergic asthma did not affect the rate of depressive symptoms in boys. Neither did their weight status.

First Nations boys, however, did have an increased risk of depression.

Girls: 3 factors increased the risk of depressive symptoms for girls in this study:

·         Having non-allergic asthma

·         Being overweight

·         Ethnicity (First Nations)

Girls with non-allergic asthma were more likely have symptoms of depression even if they weren’t overweight.

Having allergic asthma or other allergies (hay fever, eczema or food allergies) did NOT increase the rate of depressive symptoms.

These findings were surprising as researchers expected to see more depression in children with eczema, hay fever or other allergies. 

Researchers believe that the hormone Leptin may be a key factor connecting depression, weight and asthma.  Increased Leptin levels in children have been associated with non-allergic asthma (for girls), weight and depression.  More research needs to be done to better understand the effects of Leptin on the body.

This study did not look at how depressive symptoms change as the children age. It would be helpful to look at how depressive symptoms of children with and without asthma change over a longer period of time.

 Conclusion:

• It is important for doctors and educators to assess the existence of other illnesses, including depression, when assessing asthma.
• Non-allergic asthma is a risk factor for depression in girls. So is being overweight.
• Recognizing and treating depression will help improve a child’s asthma control and quality of life.

 Depression is more common in girls with non-atopic asthma. Bahreinian S, Ball G, Colman I, Becker A, Kozyrskyj A. Chest. 2011 April 7

Delay in diphtheria, pertussis, tetanus, vaccination is associated with a reduced risk of childhood asthma.

Asthma is the most common childhood disease in industrialized countries.  The increase in asthma has occurred along side improvements in hygienic standards and vaccinations.  Vaccines are important as they have prevented much illness and death.  However, researchers wonder if they play a role in the development of asthma.

Studies looking at an association between asthma and vaccinations show mixed results.  Some show that vaccines increase the risk, other show that vaccines decrease the risk and some show no association.  In other studies, researchers found that children have LESS of a risk of developing asthma if vaccines are given later.

Our research question: Does the timing of diphtheria, pertussis (whooping cough), and tetanus vaccinations (DPT) affect the development of asthma in childhood?

Research findings:

The SAGE study examined immunization and health care records of 14,000 children born in Manitoba in 1995 who still live in the   province. This study showed that children who had their first routine vaccination delayed by more than 2 months cut their risk of getting asthma in half.  Nearly 14% of children who received their first shot of diphtheria, pertussis, and tetanus vaccine at 2 months of age developed asthma, compared to 5.9% of children who were vaccinated later. The study also showed that more boys than girls developed asthma (3 boys to 2 girls) and children who developed asthma lived mostly in cities (70%). It is important to note that these children received a different type of DPT vaccine than what is used now. Children have been receiving a new version of the vaccine since late 1997.

What do these results mean?

This study tells us what is happening, but it does NOT tell us WHY it is happening. One of the main reasons children are immunized later than recommended is because the child has a fever or an infection at the time they should receive it. We know that fever or infection during the first year of life can help prevent the development of asthma. It may be that children are protected from asthma due to the fever or the infection and not because the vaccination was given later.

Conclusion:

Delaying the first vaccine (DPT) by 2 months or more is associated with lower rates of asthma in childhood.  The exact cause of the decreased rate of asthma is not clear. It is important to note that children who participated in this study received a different type of DPT vaccine than what given today.  We don't know if the same results would be seen using today’s vaccine.

The results of this study should not be used to spur a change in the province’s vaccination schedule. More research needs to be done on the new vaccine to see if the results are the same. Further research is also needed to see if early life infections are the reason for delayed immunization and protection against the development of asthma. 

The co-author of this study, Dr. Allan Becker, says: “It is important to continue to have your children immunized on the current schedule. The benefits of childhood vaccination far outweigh the risks.  The safety and effectiveness of vaccines have been studied for years. You can not use this study to predict what would happen to today’s children getting immunizations because the vaccination used now is different. There are far fewer side effects now, and even in 1995 when there was a risk of high fever, that risk was far outweighed by the benefits. In countries where immunizations went down or were delayed, childhood illnesses went up. These are serious illnesses that cause major problems and some capable of causing death in children”.

Delay in diphtheria, pertussis, tetanus vaccination is associated with a reduced risk of childhood asthma. McDonald KL, Huq SI, Lix LM, Becker AB, Kozyrskyj AL., J Allergy Clin Immunol. 2008 Mar;121(3):626-31. Epub 2008 Jan 18.

Fast Food Consumption Counters the Protective Effect of Breastfeeding on Asthma in Children?

The recent increases in asthma and allergic diseases is believed to be caused, in part, by changes in our lifestyle, including our diet.

In particular, fast food consumption has increased. Children consumed 5 times more fast food in the 1990s compared to the 1970s.  Fast food has been associated with wheezing in children, especially in boys.  It is not yet known if fast food is also associated with increased asthma.

The rates of prolonged breastfeeding (breastfeeding for more than 3 months) have also increased since the 1970s.  Some studies (but not all) suggest that prolonged breastfeeding is associated with less risk of asthma in children.

Researchers are confused as to why the increase in breastfeeding does not seem to protect children from developing asthma.

Our research questions:

• Why are asthma rates increasing despite the fact that more mothers are breastfeeding longer?
• Why is prolonged breastfeeding not protecting these children from getting asthma?
• Is the protective effect of breastfeeding changed by the increase in fast food?

723 SAGE children participated in this study.  246 with asthma and 477 without asthma.  Participants answered questionnaires asking about breastfeeding and about diet, including eating fast food. 

Children in the “Fast Food Group” were children who ate “burgers/fast food more than once or twice per week” in the past year compared to children who never or only occasionally ate burgers/fast food.

“Prolonged exclusive breastfeeding” was defined as feeding only breast milk for more than 12 weeks.

Findings:

Children with asthma were more likely to consume fast food than children without asthma.

No junk food group: Asthma was less frequent in children who breast fed for more than 12 weeks.  Breast feeding seems to have had a protective effect. 

Junk food eating group: Prolonged breastfeeding was not associated with less asthma. Breastfeeding did not seem to have a protective effect.

Children who often ate fast food and who were not breast fed for long had the highest risk of asthma compared to children who were breast fed for longer and who did not eat fast food as they got older.

Conclusion:

This study does not prove that fast food causes asthma but does show that fast food is associated with asthma in children. 

The increase in breast feeding does not seem to have protected children from developing asthma. The protective effects of breast feeding may be lost when a child eats fast food more than twice per week.

More research is needed to better understand the role of high salt/high fat foods in the development of asthma.

Fast food consumption counters the protective effect of breastfeeding on asthma in children?  Mai XM, Becker AB, Liem JJ, Kozyrskyj AL.  Clin Exp Allergy. 2009 Apr;39(4):556-61. Epub 2009 Jan 22

Ask the Researcher

“I wonder if mothers who are committed to breastfeeding make other lifestyle choices which have a positive outcome on their children’s weight – eg. More likely to walk or bike than drive; healthier food choices, etc.  This was probably taken into account in the surveys, but I can’t remember all the questions.”

The study did attempt to examine some influences such as gender, economic status, place of residence, family history of asthma etc on breastfeeding rates, obesity and asthma.  However personal lifestyle factors are difficult to tease out. 

The SAGE study, being an epidemiological study, helps researchers identify trends and associations but does not always explain the “why” of the trends.  Your question is appropriate and other lifestyle factors such as diet, activity levels, stress, may well play a role in the outcome.  The exact role they play and the exact mechanism continue to be important questions that researchers are trying to answer.