4.3 Strengths and limitations
This study has some strengths that support the validity of our findings.
First, we observed the association of eczema phenotypes with allergic
multimorbidity in the largest cohort, (N = 6,852) to date. Further, all
allergic diseases, which are considered in the atopic march, were
included in the analysis. The overall prevalence of allergic diseases
that we observed are in line with other
reports.14,15,36-39 However, eczema prevalence was
slightly higher than commonly reported.15,17,38,39This could be, partly, due to the self-/guardian-reported factors
utilized for verification of eczema presence. Prevalence of eczema
phenotypes resembled the distribution of phenotypes in the cohorts that
were used to define them initially, with the most prevalent phenotypes
(besides “Never eczema”) being “Very early onset – remitting” and
“Early onset – remitting”.7 Further, our
investigation covers a wide age-range (0 – 17 years) including infancy,
childhood, and adolescence, while many other studies assess outcomes at
a younger age. Regression models were adjusted comprehensively for
confounders, known to influence allergic disease development. Lastly,
due to the population-based study design, our findings are derived from
real-life data and do not rely on selective sampling, leading to results
representative for the general population.
However, some limitations need to be addressed. Firstly, the data used
in this study was derived from self-/guardian-reported questionnaires.
Additionally, the calculation of age of onset displayed some
imprecision, as it was based on the age brackets which had been
predefined with differing durations, resulting in estimates within those
age brackets. Further, recall bias at baseline may have been present,
since subjects had to report presence, treatment and medication of
allergic diseases since birth. Lastly, due to the Lifelines cohort
exclusively consisting of participants based in the Northern
Netherlands, our results are subject to a regional bias. However, as
described above, our data is in line with findings from comparable
cohorts.