No significant deviation from Hardy–Weinberg proportions was found for rs17822931 for white mothers (χ2
=0.129) or for white children (χ2
=0.458). The analysis of ascertainment bias in rs17822931 (Supplementary Figure S1
online) showed a slight but nonsignificant (P
=0.129) excess of rs17822931 AA homozygotes (115 expected vs. 134 observed), again indicating that genotyping error or unrecognized subdivision through admixture or stratification was not an issue in our analyses. Minor allele frequencies were 12.5% for white mothers and 24.9% for non-white mothers. Similar results were observed for the child genotype: 12.7% (white parentage), 15.1% (mixed parentage), and 20.7% (non-white parentage). Average usage of deodorants was 6.1 times per week for mothers (SD=1.90) and 5.2 times per week for partners (SD=2.53). There was lower usage among non-white parents by 10–16% (P
We describe below a summary of the observed results for nonexperts in statistics. A more detailed description of the results, including specific statistical evidence supporting our findings, can be seen in Supplementary Appendix S1
We observed a strong association between deodorant usage and maternal rs17822931 genotype in ALSPAC for both white and non-white participants. The association was highly significant for white mothers (P=1.8 × 10−14) and for non-white mothers (P=1.5 × 10−6; ).
Associations between the use of deodorant by the mother at 8m and by the partner during pregnancy and ABCC11 (rs17822931)
However, there was no association between maternal genotype and partners' deodorant usage in whites (P=0.9040). The rs17822931 genotype in children associated with similar effect sizes for deodorant usage by the mother and by the partner. When considering white individuals, the rs17822931 genotype of the child associated significantly with maternal deodorant usage (P=0.0004) and with the use of deodorant by the partner (P=0.0235).
Five other putative confounders were considered in linear regression analysis of maternal deodorant use on maternal genotype (). Significant associations were observed for four of them (maternal age, maternal education, housing tenure, and hygiene), with no significant effect for paternal social class. The relative effect of the rs17822931 genotype was larger than the effect of each of these variables. The greater effect ranged from 3 times higher than hygiene to 34 times higher than maternal education, as measured by the β-coefficients observed in linear regression analyses ().
Linear regression analysis of maternal deodorant use on maternal genotype (recessive model) adjusted for five confounders (N=4,903)
Results from contingency tables
Results from contingency tables () allow the identification of more specific effects for each of the categories of deodorant usage in relation to rs17822931. The results for deodorant usage in four combinations of individuals were as follows.
Association of genotype with deodorant usage
Maternal genotype association with maternal deodorant usage
shows that there is a significantly higher than expected frequency of the AA genotype in white mothers with a lower use of deodorant. There is a nearly a 5-fold overrepresentation of AA individuals in the deodorant never use group, with significant overrepresentations in all other categories except in the category of daily deodorant usage. In this category, the observed frequency of AA homozygotes is significantly lower than that expected. Overall, there is a significant (P
=3.7 × 10−20
) difference between the observed and the expected numbers in the contingency table for deodorant usage and the rs17822931 genotype. These results are for the additive model. They are very similar to the results observed under the recessive model (Supplementary Table S1
shows the relationship between rs17822931 genotypes and both an odoriferous steroid (data from Martin et al., 2010
) and deodorant usage. AA homozygotes (with the lowest production of the odoriferous steroid) showed the highest ratio of never use over daily deodorant use. The converse was found for GG homozygotes. AG heterozygotes showed differences in relation to GG homozygotes, with both lower production of the odoriferous steroid and significantly (P
=0.002) higher ratio of never use over daily deodorant use than GG homozygotes.
Figure 1 Relationship between an odoriferous steroid and rs17822931 single-nucleotide polymorphism (SNP) genotype and between deodorant use and the rs17822931 SNP genotype. (a) Concentration of the odoriferous steroid 5α-androst-16-en-3-one observed for (more ...) Child genotype association with maternal deodorant usage
The results from the contingency table analyzing white children's rs17822931 genotype by maternal deodorant usage ( and Supplementary Table S2
online) are different from the results observed in white mothers. There is an increased proportion of children with AA and GA genotypes in the category of never use of deodorant in white mothers. However, this increase is not as important as the one observed in deodorant usage of white mothers according to their own rs17822931 genotype. Overall, there is a significant (P
=0.010) difference between the observed and expected frequencies under the additive model (), although these differences are not significant (P
=0.173) under the recessive model (Supplementary Table S2
Child genotype association with partner's deodorant usage
and Supplementary Table S3
online show partner's deodorant usage according to children's rs17822931 genotype. No significant differences were observed in the contingency tests either under the additive model (P
=0.170) or under the recessive model (P
Maternal genotype association with partner's deodorant usage
Similar results were observed for the analyses of partner's deodorant usage stratified by maternal rs17822931 genotype (Supplementary Tables S4 and S5
Prediction of parental deodorant usage on the basis of the child's genotype
Supplementary Figure S2
online shows the expected child genotype–parent phenotype associations based on parents' genotypes, allele frequency, and proportions of never use over daily use of deodorant for each genotypic category, assuming a recessive model and restricting to white mothers. For maternal genotype–phenotype associations, we found good agreement between the observed ratios in children for each genotype and the liability predictions computed from parents.
Percentage of deodorant usage: mothers versus partners
The percentage of ALSPAC partners using deodorant daily or on most days (82.7%) is significantly lower (P=5.3 × 10−74) than the percentage for mothers using deodorant daily or on most days (93.3%). The figures are computed from and are as follows: 945 partners using deodorant approximately once a week or less and 4,502 partners using it on most days or daily; and 433 mothers using deodorant about once a week or less and 6,062 mothers using it on most days or daily.
shows that 77.8% of women with the AA genotype still use deodorant (at least once a week week), compared with 80.0% of male parents of children with the AA genotype who use deodorant at least once a week ().
also shows that the proportion of women with the GG genotype who do not use deodorant (<1 per week or never) is much reduced (4.7%) compared with 13.0% of male parents of children with the GG genotype who never use deodorant or use it <1 per week ().