Increased Risk of Childhood Asthma From Antibiotic use in Early Life

The rates of asthma have increased all over the world but especially in industrialized countries with clean water and better health care systems. Several theories are being studied to try to understand the cause of this.

The “Hygiene Hypothesis” stems from a belief that growing up in cleaner environments affects the development of a child’s immune system differently than growing up in an environment with more bacteria. That is why children who grow up in the country or on farms seem to have lower rates of asthma than children who are raised in the city. 

Researchers also think that the presence of microbes in our intestines helps our immune system to develop properly and that the use of antibiotics early in life disturbs the amount of normal gut microbes. This then affects the development of a baby’s immune system. 

Our research questions:

• Does taking antibiotics in the first year of life affect the chances of a child developing asthma by age 7 years?
• Are these results different for children living in the city vs children living in the country?
• Are all antibiotics associated with changes in the rates of asthma?

Antibiotics were divided into 2 groups, Broad spectrum (BS) and Narrow spectrum (NS).

Broad spectrum antibiotics are antibiotics that can kill a large range of different bacteria. Examples of broad-spectrum antibiotics are: Amoxicillin, Ampicillin, Tetracycline, Chloramphenicol, and Ciprofloxacin.

Narrow spectrum antibiotics are active against a select group of bacteria. Examples of Narrow spectrum antibiotics are: Penicillin, Cloxacillin, Cephalexin, Cefadroxil, and Erythromycin.

Researchers also looked at other risk or protective factors and divided groups of children according to: gender, rural vs urban living environment, family income, family history of asthma (mother with asthma) and the number of children in the home.

Findings:

65% of children in the SAGE study received at least one prescription for antibiotics during their first year of life.

- 52% had received a broad spectrum antibiotic only

- 3% had received a narrow spectrum antibiotic only

- 10% had received both types of antibiotics

Illnesses treated with antibiotics include:

- Ear infections (40%)

- Upper respiratory tract infections (28%)
- Lower respiratory tract infections (19%)

- Non-respiratory tract infections (7%)

• The use of Broad Spectrum antibiotics in the first ear of life increased the chances of a child developing asthma by age 7.  The more courses of antibiotics a child had, the higher the chance of getting asthma.

• Children who received more than 4 courses of Broad spectrum antibiotics in the first year were almost twice as likely to get asthma by age 7. 

• Children most at risk of the effects of antibiotics were children living in the country and children who DID NOT have a dog in the home when they were babies. A possible explanation for this is that children who live in the city and who do not have a dog already have lower levels of bacteria in their gut and that taking antibiotics does not change that much.  In essence, children who are naturally exposed to higher levels of bacteria (eg: those who live on farms or who have pets) have the most to lose. The amount of bacteria in their gut changes more dramatically with antibiotics and their immune system changes accordingly.

• Children whose mothers did not have asthma also seemed more sensitive to the effects of antibiotics. The reason for this is not understood but may have to do with some inherited genetic difference.

Conclusion: Use of antibiotics in early childhood puts all children at higher risk of getting asthma by age 7 years. Some children are more at risk of this than others. The exact reasons for this are not yet clear. 

Broad spectrum antibiotics seem to increase the risk the most.  More studies need to be done to understand this better. In the mean time, it is suggested that frequent use of Broad spectrum antibiotics be avoided as much as possible in the first year of life.  Doctors continue to be advised to only use antibiotics when absolutely necessary.

Increased risk of childhood asthma from antibiotic use in early life.Kozyrskyj AL, Ernst P, Becker AB. Chest. 2007 Jun;131(6):1753-9. Epub 2007 Apr

Infrequent milk consumption plus being overweight may have great risk for asthma in girls.

It is believed that the dramatic increase in childhood asthma and allergies in the past 25 years is caused by changes in our lifestyle including the North American diet. Children, and in particular teen girls, drink 36% less milk than they did 20 years ago.

• Some studies suggest that drinking milk is associated with lower rates of asthma. 
• Drinking milk has also been associated with better weight in children.
• Being overweight is associated with more asthma symptoms in children.

 Our research questions:

• What role does low milk consumption play in the development of asthma in children 8-10 years old? 
• What role does being overweight play in the rate of asthma?
• Does the combination of low milk consumption AND overweight together increase the risk of asthma more than each component alone?

 Children were divided into 2 groups Those with asthma and those without.

Each of these two groups was further divided into 2 more groups: Low milk consumption (drinking milk less than 2 times per week) and Regular milk consumption (drinking milk more than 2 times per week).

Overweight was defined as having a Body Mass Index of greater than 85% of the average for the child’s age.

Findings:

• Over all, children who drank little milk were more likely to be overweight.
•  Children with asthma ate fast foods more often than the children without asthma.
•  Girls with asthma tended to drink milk less often than girls who did not have asthma. This was not seen in boys with asthma. 

• Girls with asthma had a higher incidence of being overweight than girls without asthma.  
• Girls who drank little milk and were overweight were even more likely to have asthma.  This was true weather the girl lived an other-wise healthy lifestyle or not (eg, no smokers in the home, being active, eating fish and other foods with Vitamin D). 

• The number of boys who were overweight was the same for boys with or without asthma.

Conclusion: Drinking milk more often was associated with healthier weight. Not drinking milk regularly was associated with a higher incidence of asthma in girls. This was especially true if the girl drank little milk AND was overweight.  Girls who have a healthy weight and drink milk regularly have a lower incidence of asthma.

The reason for this is unclear and the researchers want to continue to study this to understand how diet and weight play a role in asthma.

Infrequent milk consumption plus being overweight may have great risk for asthma in girls. Mai XM, Becker AB, Sellers EA, Liem JJ, Kozyrskyj AL. Allergy. 2007 Nov;62(11):1295-301

The Relationship of Breast-feeding, Overweight, and Asthma in Preadolescents

Breast feeding has many advantages.  It has been shown to improve the physical and emotional health of both the mother and the infant.  The longer a baby has breast milk, the better the health outcomes.

Children who are breastfed for shorter periods of time (less than 3 months) seem to be at increased risk of being overweight once they get older.

Children who are overweight have an increased risk for developing asthma.

Our research question: Are children who were only breast fed for a short amount of time AND who were overweight more likely to have asthma?  If so, what environmental and genetic traits did being overweight and having asthma share?

Findings:

• Children who were not breastfed or only breastfed for a short amount of time (less than 3 months) were slightly more likely to have asthma at age 8-10 years.

• Children who were not breastfed or breast fed for less than 3 months were more likely to be overweight by age 8-10years.

• Children who were not breast fed or breast fed for less than 3 months AND were overweight had the highest risk of asthma.  This was especially true in boys and in children whose mothers have asthma. 

• Being overweight may be a consequence of little or no breastfeeding and may increase the risk of asthma in susceptible children (those with a family history of asthma for example).

• This association may be due to a hormone called Leptin. Leptin plays a role in controlling food intake, which helps maintain good body weight. Leptin may also affects a child’s immune response.  Levels of Leptin are higher in children who are breast fed. This may lead to better weight control and less asthma.

• Obesity in a mother is one of the strongest risk factors for a child being obese.  It is also associated with difficulty breastfeeding.  However, a mother being obese does not increase the risk of a child having asthma.

Conclusion: Doctors and nurses have long been encouraging women to breastfeed for as long as they can.  This study gives doctors, nurses, teachers and prenatal educators more reasons to continue to help and encourage mothers to breastfeed as long as they can.

To read the published article, go to: The relationship of breast-feeding, overweight, and asthma in preadolescents.Mai XM, Becker AB, Sellers EA, Liem JJ, Kozyrskyj AL. J Allergy Clin Immunol. 2007 Sep;120(3):551-6. Epub 2007 Jun 21

Continued Exposure to Maternal Distress in Early Life is Associated with an Increased Risk of Childhood Asthma

Evidence is emerging that a mother’s stress in early life plays a role in the development of childhood asthma. Increase in chronic stress of women has matched the rising rate of asthma in the Western world. Stress is a well-known cause of worsening asthma in children. Research suggests that a mother’s stress in early life may lead to the development of asthma in kids. Parenting difficulties in the first year of life have been associated with asthma at ages 6-8.

A child’s nervous and immune system reacts to stress in a way that increases the development of asthma.  These stress responses are exaggerated in children if the mother’s stress was present when she was pregnant. Others have identified that depression in a mother, is especially “toxic” and can lead to the development of asthma. Depressed mothers demonstrate less affection and fewer responses to infant cues. Their infants spend more time fussing and crying, and exhibit more stress behaviours compared with infants of mothers who are not depressed.

Our research questions:

• Does a mother’s stress increase the chances of a child developing asthma? 

• Is this different for children who are more prone to getting asthma (because of someone in the family has asthma) compared to children who are not?

Findings: The SAGE Study assessed the risk of asthma at age 7 in relation to their mother’s level of stress in the first year of life and onward.

• Among the 13, 907 children born in Manitoba in 1995, 18.9% were exposed to significant maternal distress during their first year of life.

• 8.3% of the children who were exposed to a lot of maternal stress during the first year of life had asthma at 7 years of age. Only 6.2% of the children who were not exposed to maternal stress had asthma. Seventy-five percent of children with asthma received their first diagnosis of asthma after the age of one year.

• A mother’s stress did increase the rate of asthma in childhood.  The more stress the mother had, the higher the risk to the child. The children most at risk were those whose mothers had long term stress. These children had 1.6 times higher risk of asthma at age 7 years.

Children whose mother had short term stress (for example only during the first few months after birth) were NOT at an increased risk of having asthma.

• A mother having asthma, being a boy, living in the city, and the number of times a child had to see a doctor were all associated with a higher risk for asthma in children. 

Having more children in the family was associated with a lower risk of asthma.

• Even children whose mothers did NOT have asthma, had a higher risk of developing asthma if their mother was under significant prolonged stress during their first years of life.

Conclusion:. Exposure to long term maternal stress, starting from birth, is associated with an increased risk of getting asthma for kids.  The possible reasons for this are complex. More research needs to be done to better understand this relationship.

Definitions:

Current asthma at age 7 was defined as at least two physician visits for asthma, one asthma hospitalization, or two prescriptions for any asthma drug in the year after the child’s 7^th birthday.

Maternal distress was determined on the basis of physician visits, hospitalizations, or prescription medications for depression or anxiety during the first year of life and afterward. 

To see the original research article, see:

Continued exposure to maternal distress in early life is associated with an increased risk of childhood asthma. Kozyrskyj AL, Mai XM, McGrath P, Hayglass KT, Becker AB, Macneil B. Am J Respir Crit Care Med. 2008 Jan 15;177(2):142-7. Epub 2007 Oct 11.

Allergies: Why we get them

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