The primary objective of the PACT study is to study the efficacy of an intervention on three assumed risk factors for atopic disease as atopic dermatitis (AD), asthma, and allergic airway disease (AAD) including allergic asthma and allergic rhinoconjunctivitis, in an unselected population of pregnant women and small children. Further to study the effectiveness on the incidence of asthma and allergic disease from intervening on these risk factors:

• Omega-3- fatty acid intake
• Environmental tobacco smoke (ETS) exposure
• Indoor “dampness”

The prospective and longevity structure of the PACT study enables etiological studies as prospective and nested case-cohort studies, and controlled clinical trials. Accordingly, three sub-studies, and an end-point study, were designed. Questionnaires on heredity, environmental exposure, diet and on health and diseases as endpoints are collected consecutively from pregnancy, at six weeks, and at 1, 2 and 6 years of age.

The main study
Objective: To study the efficacy and effectiveness of primary prevention of asthma, AAD and AD in small children.

Design and method: PACT is a controlled, prospective, population based intervention study in primary health care. Since a ordinary Randomised Trial was impracticable a modified controlled design, following the recommendations from TREND (ref) was chosen.

A control cohort was established to track fluctuations in risk factor levels, to provide comparison data to study the efficacy of the intervention on risk factors and effectiveness on the incidence of atopy and allergic diseases. Data on risk factors are collected repeatedly through questionnaires in pregnancy, at six weeks after delivery, and at one and two years of age. The control cohort also includes a survey of occurrence of atopic diseases through questionnaires and clinical examination on endpoints at two and six years of age. These children (14.000) received the ”usual” follow up from the Primary Health Care services.

Settings: Data collection and intervention takes place in primary health care in Trondheim.

Subjects: All children born between January 1994 and December 2002 in Trondheim were recruited in the control cohort, beginning in September 2000.

The intervention started in June 2002, and the same procedure is followed in collecting data and assessing endpoints. According to power estimations the intervention group needed to include 3000 children including 30% missing in follow-up. Some 2860 children were eventually included.

Intervention: The participants receive a structured intervention on reduced tobacco exposure, improved indoor-climate by reducing housing dampness and increased intake of omga-3-fatty acids. The intervention starts in pregnancy and continues until the children are two years of age.

Main outcome measure: Changes in level of risk factor exposure and changes in incidence of asthma, AAD and AD.

Status: Nearly 14000 children are recruited in the control group, and 2860 children are included in the intervention group. The control group is well suited for conducting observational studies addressing associations between exposure and atopic disease.