Twin Studies of Atopic Dermatitis: Interpretations and Applications in the Filaggrin Era

Table 2

Population-based twin studies of the association between atopic dermatitis and asthma.

Study	Country	Age; (years)	(pairs)	Phenotypic correlation	Proportion due to genetic factors (%)	Diagnostic method
Lichtenstein and Svartengren (1997) [10]	Sweden	7–9	1339	0.30	85	Parent-report
Thomsen et al. (2006) [15]	Denmark	12–41	11231	0.40	81	Self-report
van Beijsterveldt and Boomsma (2007) [16]	Netherlands	5	8633	0.55	82	Parent-report

Phenotypic correlation is the correlation between the individual liabilities to atopic dermatitis and asthma.
Proportion due to genetic factors is the proportion of phenotypic correlation explained by genetic factors shared between atopic dermatitis and asthma.