A small but growing body of evidence points to a relationship between psychosocial stress and the early onset of asthma in children with a genetic predisposition to the disease. Specifically, clinical judgment of "early parenting difficulties" is now known to be a significant predictor for the development of asthma in genetically at-risk children.

The W.T. Grant Foundation Asthma Risk Study was designed to prospectively examine children who were considered to be genetically at-risk for developing asthma. Since the longitudinal study began in 1985, researchers have monitored both physiological and psychological factors among 150 families with the intent of identifying risk factors for illness expression.

Data currently under review for publication indicate that psychosocial predictors measured early in life are associated not only with early asthma onset, but also with the persistence of asthma to age 8 in the study cohort. The relationships between first-year variables and school-age asthma support the belief that asthma begins in the first year of life.

Follow-up is continuing on this cohort of children; it will be possible to determine whether these early psychosocial influences continue to relate to the occurrence of asthma when the subjects are 13 years old.

Environmental risk factors

Medical professionals consider asthma a familial illness. Family studies have demonstrated a significantly increased risk for the development of asthma in individuals who have affected relatives. However, genetic vulnerability does not guarantee that an individual will develop asthma.

It is now accepted that the expression of asthma involves a genetic predisposition combined with exposure to environmental factors. Researchers have extensively investigated a number of environmental factors in terms of their role in the onset of asthma.

• Respiratory viral infections - Clinical studies have demonstrated that the onset of asthma is often preceded by respiratory infections.
• Specific antigens - Antigens from dust mites, molds, animal dander, and cockroaches may stimulate a classic antibody response involving immunoglobulin E antibodies.
• Nonantigenic irritants - Although smoke is the predominant substance in this category, a wide range of air pollutants may directly affect bronchial receptor systems or act through potentiating allergic mechanisms.
• Emotional stressors - Stress may lead to increased bronchial sensitivity or inhibit the immune response.

There is supportive data for the role of each of the first three categories of exposures, although the significance and the mechanisms of each of them continue to receive extensive research attention. In contrast, the last of the four, emotional stressors, has received minimal consideration up to now. The W.T. Grant study has spent the last 14 years examining the associations among parental behavior, emotional stressors and later illness expression in genetically at-risk children. The data currently under review provide support for the contribution of psychosocial factors to asthma onset and persistence into childhood.

Parenting issues

The initial phase of the Grant study examined perinatal variables and the subsequent health status of the children in the sample cohort. To determine the ability of the primary caregiver (typically the mother) to cope with stress and modulate the effect of stress upon the children in the study, scales were developed and used in in-home interviews with the families three weeks after the baby was born.

In order to rate parenting skills, researchers examined the following six characteristics:

• Parents' attitudes toward the infant
• Parents' sensitivity to the infant's needs
• Parents' strategy for sharing parenting responsibilities
• Evidence of parents' disturbed emotional adjustment that would affect infant care (e.g., postpartum depression)
• Adequacy of parents' plan to continue with employment while providing adequate child care

Asthma onset

For the purpose of characterizing respiratory illness with bronchoconstriction, researchers defined three classes:

• Asthma - based on conservative diagnostic criteria that included recurrent wheezing episodes documented by the child's pediatrician, including at least one precipitated by an environmental trigger other than respiratory infection
• Infectious Wheezing - defined as multiple wheezing episodes, each associated with a respiratory infection
• Single Wheezing Episode - classified as a single wheezing episode identified by the child's pediatrician that could have occurred with or without a respiratory infection.

Using information from the children's medical records, the children were classified into one of the above categories at age 3. Fourteen of the 150 were classified as having asthma (as defined above) and 19 were considered to have infectious wheezing. Twenty-four experienced a single wheezing episode, and the remainder demonstrated no wheezing at all.

Parenting difficulties and asthma onset

The clinical judgment of "early parenting difficulties" emerged as a predictor of asthma at age 3. Fifty-two of the infants had parents whose ability to deal with the child elicited concern during the in-home interview. Of those infants, 9 (17.3%) subsequently developed asthma, compared with 5 (5.1%) of those infants whose parents were perceived as parenting their infant well.

The parenting difficulties that were related to asthma onset were highly associated with the other interview ratings, and provide insight into the range of problems captured by ratings of parenting difficulties. Mothers who were rated as having parenting difficulties were significantly more likely to be coded as coping poorly than were those judged to have adequate parenting skills. Similarly, difficulties in modulating the child's affect were highly significantly associated with ratings of parenting risk. Postpartum depression was rare in this sample, but when it did occur, depressed mothers were always coded as having parenting difficulties. Both the interview ratings and the Dyadic Adjustment scale indicated that problematic marital satisfaction was highly associated with parenting risk.

Parenting skills and stress regulation

Conceptually, quality parenting modulates or buffers infants from external stress. If this were true, the infants in the W.T. Grant study whose parents demonstrated superior parenting skills would be protected from illness despite high or low levels of stress.

Researchers divided the sample into four groups based on stress levels reported using the Family Inventory of Life Events (FILE), a family-oriented inventory of life events designed to assess the impact of stressors in multiple family members, and parenting risk ratings. The categories were:

• High stress/adequate parenting
• Low stress/adequate parenting
• High stress/problematic parenting
• Low stress/problematic parenting

Only 5.3% of children in families with low stress and adequate parenting developed asthma by age 3, compared with 25% of children in families categorized as having high stress and problematic parenting. Also, 4.4% of children in families with high stress and adequate parenting and 10.7% of children in families with low stress and problematic parenting expressed asthma.

Possible predictors

The relationships between risk factors and asthma onset have still not been clearly defined. Few studies have included an adequate assessment of psychosocial variables among the variety of predictive factors that have been examined. But the inclusion of psychosocial assessments adds an important dimension to efforts to define the relationships between risk factors and asthma onset.

The W.T. Grant study identified risk factors from previous studies, and measured them prospectively in this cohort. Only four of the risk factors - frequent illness, 6-month IgE, parenting difficulties and eczema - demonstrated statistically significant associations with the early onset of asthma. The occurrence of frequent infectious illness during the first year of life was the strongest predictive risk factor for the onset of asthma by age 3. Elevated serum IgE measured at 6 months was a second independent and significant predictor for early asthma onset. While IgE was a significant predictor, only 24% of the children who went on to develop asthma by age 3 years had an early elevation of total serum IgE at 6 months.

An association between the third predictive factor, early parenting difficulties, and the onset of asthma had not been previously demonstrated. The association is particularly striking since it was independent of both frequent infectious illness and elevated total serum IgE. There are a number of possibilities that might account for the relationship between early parenting and asthma onset. The parenting ratings at 3 weeks of age is likely related to parenting behavior over the following years, and may thus be a marker of parents' illness management. Parents who are able to respond promptly and effectively to early illness may play a role in delaying or preventing early asthma onset. Alternatively, the quality of early caregiving may affect the developing immune system through mechanisms that are as yet unknown.

Eczema was the fourth variable that was more prevalent among children who developed asthma by age 3. But, the occurrence of eczema did not add to the strength of the prediction after the first three variables.

The relationship between any risk factor and the onset of asthma continues to be the focus of investigations both nationally and throughout the world. But, the documentation does provide potential guidance for asthmatic parents who seek advice on minimizing their child's risk of developing asthma. Given these findings, asthma prevention efforts could be designed to reduce exposure to multiple risk factors.

Mary Klinnert, Ph.D. is Associate Faculty Member in Pediatrics at National Jewish Medical and Research Center and Associate Professor in Psychiatry at University of Colorado Health Sciences Center.

References

Klinnert MD, Mrazek P, Mrazek DA: Early asthma onset: The interaction between family stressors and adaptive parenting. Psychiatry 1994; 57:51-61.

Mrazek DA, Klinnert MD, Mrazek P, et al. : Prediction of early onset asthma in genetically at risk children. Pediatric Pulmonology 1999; 27:85-94.