A longitudinal examination of perinatal testosterone, estradiol and vitamin D as predictors of handedness outcomes in childhood and adolescence

Figures & data

Figure 1. Histograms of the raw (a) and natural log transformed (b) scores for perinatal umbilical cord free testosterone.

Table 1. Descriptive statistics for hormonal, sociodemographic, obstetric, antenatal, and handedness variables.

		Overall sample			Males			Females
Continuous variables		n	M	SD	n	M	SD	n	M	SD
Free testosterone (pmol/L)		527	7.80	6.87	280	9.56	7.81	247	5.80	4.91
Estradiol (nmol/L)		548	28.25	17.15	283	28.95	16.58	265	27.49	17.74
Vitamin D (25[OH]D) (nmol/L)		596	57.78	18.80	249	57.55	17.96	347	57.94	19.39
Y10 right-hand speed		693	35.81	7.13	331	35.76	7.48	362	35.85	6.81
Y16 right-hand speed		526	39.43	7.56	248	41.82	7.63	278	37.29	6.84
Y10 left-hand speed		694	32.48	7.11	333	32.97	7.10	361	32.03	7.11
Y16 left-hand speed		527	37.43	7.09	248	39.69	6.94	279	35.42	6.61
Y10 LI (signed)		687	0.10	0.22	328	0.08	0.21	359	0.12	0.23
Y16 LI (signed)		526	0.05	0.16	248	0.05	0.17	278	0.05	0.15
Y10 LI (unsigned)		687	0.16	0.18	328	0.16	0.16	359	0.17	0.19
Y16 LI (unsigned)		526	0.12	0.12	248	0.12	0.13	278	0.11	0.11
Birth weight		549	3229.28	598.10	266	3233.50	558.12	283	3225.30	634.34
Gestational age at birth		747	274.31	15.38	358	274.73	15.12	389	273.92	15.63
Maternal age at conception		747	28.21	5.75	358	28.18	5.74	389	28.24	5.76
Age at Y10		748	10.59	0.18	358	10.60	0.17	390	10.58	0.20
Age at Y17		637	17.07	0.29	299	17.06	0.28	338	17.08	0.29

Nominal variables		Overall n (%)	Male n (%)	Female n (%)
Y10 hand preference	Right	619 (88.05%)	296 (87.57%)	323 (88.49%)
	Left	84 (11.95%)	42 (12.43%)	42 (11.51%)
Y16 hand preference	Right	471 (89.20%)	222 (89.16%)	249 (89.25%)
	Left	57 (10.80%)	27 (10.84%)	30 (10.75%)
Sex	Female	400 (52.15%)	0 (0.00%)	400 (100.00%)
	Male	367 (47.85%)	367 (100.00%)	0 (0.00%)
Labour onset	Present	657 (87.95%)	311 (86.87%)	346 (88.95%)
	Absent	90 (12.05%)	47 (13.13%)	43 (11.05%)
Maternal smoking	No	114 (33.93%)	57 (34.34%)	57 (33.53%)
	Yes	222 (66.07%)	109 (65.66%)	113 (66.47%)
Maternal alcohol consumption	No	405 (54.29%)	187 (52.23%)	218 (56.19%)
	Yes	341 (45.71%)	171 (47.77%)	170 (43.81%)
Season of birth	Spring	180 (23.47%)	79 (21.53%)	101 (25.25%)
	Summer	247 (32.20%)	118 (32.15%)	129 (32.25%)
	Autumn	189 (24.64%)	90 (24.52%)	99 (24.75%)
	Winter	151 (19.69%)	80 (21.80%)	71 (17.75%)
Parental handedness	Neither non-right-handed	624 (83.76%)	304 (84.92%)	320 (82.69%)
	Either/both non-right-handed	121 (16.24%)	54 (15.08%)	67 (17.31%)
Average parental education	None	187 (25.03%)	86 (24.02%)	101 (25.96%)
	Trade certificate/apprenticeship	214 (28.65%)	100 (27.93%)	114 (29.31%)
	Professional registration	167 (22.36%)	79 (22.07%)	88 (22.62%)
	College diploma/degree	93 (12.45%)	50 (13.97%)	43 (11.05%)
	University degree	86 (11.51%)	43 (12.01%)	43 (11.05%)
Annual family income	< AUD$7,000	43 (5.94%)	23 (6.61%)	20 (5.32%)
	AUD$7,000-11,999	61 (8.43%)	29 (8.33%)	32 (8.51%)
	AUD$12,000-23,999	180 (24.86%)	82 (23.56%)	98 (26.06%)
	AUD$24,000-35,000	189 (26.11%)	89 (25.58%)	100 (26.60%)
	≥ AUD$36,000	251 (34.67%)	125 (35.92%)	126 (33.51%)

Note. Age at Y16 was not recorded when handedness tasks were completed, so we used age at the Y17 follow-up as a proxy. Parental educational attainment was calculated as follows. First, those who responded with “Other” were recoded as “Trade certificate/apprenticeship” because this was the modal value for both males and females, and because “other” implies more than “none”. Second, missing values were replaced with those of participants’ partners when such information was available. (Prior to this imputation, maternal and paternal educational attainment were moderately correlated, rs [650] = 0.361, p < 0.001.) Finally, the average of maternal and paternal educational attainment was taken and rounded to the nearest integer (i.e., to the nearest attainment category).

Figure 2. Boxplots for relative hand skill LI (signed) stratified by hand preference (right or left) at Y10 (a) and Y16 (b).

Table 2. Bootstrapped (10,000 samples) Pearson’s correlations between hormonal predictors and handedness outcomes, stratified by sex.

			Hand preference			Signed relative hand skill			Unsigned relative hand skill			Right-hand speed			Left-hand speed
Sex	Age	Hormone	n	rpb	BCa 95% CI	n	r	BCa 95% CI	n	r	BCa 95% CI	n	r	BCa 95% CI	n	r	BCa 95% CI
Male	Y10	Free testosterone (ln)pmol/L	255	0.102	−0.033–0.255	251	−0.059	−0.168–0.059	251	−0.035	−0.140–0.093	253	−0.136	−0.258 – −0.004	253	−0.059	−0.188–0.082
		Estradiol nmol/L	258	−0.060	−0.153–0.048	254	0.062	−0.106–0.199	254	0.191	0.057–0.328	256	0.059	−0.094–0.211	256	−0.020	−0.133–0.085
		Vitamin D nmol/L	230	0.051	−0.046–0.146	224	−0.042	−0.150–0.082	224	−0.097	−0.202–0.047	225	0.021	−0.113–0.156	227	0.051	−0.084–0.181
	Y16	Free testosterone (ln)pmol/L	–	–	–	191	−0.054	−0.196–0.082	191	0.004	−0.139–0.171	191	−0.104	−0.253–0.041	191	−0.086	−0.239–0.073
		Estradiol nmol/L	–	–	–	192	0.105	−0.031–0.230	192	0.008	−0.113–0.151	192	0.036	−0.094–0.157	192	−0.048	−0.172–0.082
		Vitamin D nmol/L	–	–	–	168	0.043	−0.085–0.154	168	−0.003	−0.139–0.128	168	0.038	−0.109–0.172	168	0.004	−0.150–0.156
Female	Y10	Free testosterone (ln)pmol/L	222	−0.050	−0.170–0.090	219	0.037	−0.112–0.212	219	−0.017	−0.167–0.194	219	0.015	−0.131–0.202	221	−0.050	−0.172–0.081
		Estradiol nmol/L	238	−0.065	−0.152–0.042	234	0.011	−0.100–0.120	234	−0.020	−0.125–0.084	235	0.078	−0.063–0.223	236	0.043	−0.065–0.154
		Vitamin D nmol/L	314	0.033	−0.077–0.148	309	−0.136	−0.216 – −0.045	309	−0.124	−0.202 – −0.038	312	0.024	−0.085–0.137	310	0.120	0.020–0.214
	Y16	Free testosterone (ln)pmol/L	–	–	–	175	0.032	−0.122–0.192	175	−0.049	−0.185–0.098	175	−0.064	−0.208–0.076	176	−0.077	−0.206–0.055
		Estradiol nmol/L	–	–	–	186	0.128	−0.006–0.255	186	0.008	−0.117–0.174	186	0.007	−0.107–0.127	187	−0.093	−0.216–0.035
		Vitamin D nmol/L	–	–	–	234	−0.077	−0.231–0.083	234	−0.184	−0.301 – −0.059	234	0.028	−0.096–0.150	235	0.101	−0.015–0.224

Note. Hand preference is coded as 0 = right handed, 1 = left handed.

Table 3. Bootstrapped (10,000 samples) multivariate regression models with hormones as predictors and handedness measures as outcomes.

		Step 1	Step 2		Step 3
Outcome	Predictor		β	BCa 95% CI	β	BCa 95% CI
Y10 hand preference	Testosterone		−0.495	−2.761–1.664	−0.093	−2.760–2.416
	Testosterone × Sex		0.444	−0.890–1.758	0.327	−1.289–1.905
	Estradiol		−0.031	−0.114–0.037	−0.044	−0.150–0.042
	Estradiol × Sex		0.012	−0.029–0.057	0.021	−0.030–0.079
	Vitamin D				−0.002	−0.078–0.071
	Vitamin D × Sex				0.004	−0.039–0.046
	n	684	466		313
	Model fit (McFadden Pseudo R^2)	0.03	0.03		0.04
Y10 relative hand skill (signed)	Testosterone		0.067	−0.073–0.215	0.119	−0.031–0.275
	Testosterone × Sex		−0.051	−0.135–0.027	−0.086	−0.179–0.0002
	Estradiol		−0.0004	−0.004–0.003	−0.0005	−0.004–0.004
	Estradiol × Sex		0.001	−0.002–0.003	0.001	−0.002–0.004
	Vitamin D				−0.001	−0.005–0.002
	Vitamin D × Sex				0.0002	−0.002–0.003
	n	668	459		311
	Model fit (adjusted R^2)	0.007	0.010		0.018
Y16 relative hand skill (signed)	Testosterone		−0.003	−0.094–0.096	0.019	−0.085–0.130
	Testosterone × Sex		−0.002	−0.062–0.053	−0.016	−0.091–0.053
	Estradiol		0.002	−0.001–0.004	0.002	−0.001–0.005
	Estradiol × Sex		−0.0004	−0.002–0.001	−0.001	−0.003–0.001
	Vitamin D				−0.003	−0.006 – −0.001
	Vitamin D × Sex				0.002	−0.0002–0.004
	n	516	360		240
	Model fit (adjusted R^2)	0.002	−0.004		0.024
Y10 relative hand skill (unsigned)	Testosterone		0.005	−0.107–0.131	0.074	−0.044–0.207
	Testosterone × Sex		−0.005	−0.075–0.057	−0.051	−0.126–0.014
	Estradiol		−0.001	−0.004–0.001	−0.002	−0.005–0.001
	Estradiol × Sex		0.002	−0.0001–0.003	0.002	0.0000–0.004
	Vitamin D				0.0001	−0.003–0.002
	Vitamin D × Sex				−0.0005	−0.002–0.001
	n	668	459		311
	Model fit (adjusted R^2)	0.015	0.019		0.014
Y16 relative hand skill (unsigned)	Testosterone		−0.023	−0.085–0.039	−0.030	−0.106–0.043
	Testosterone × Sex		0.008	−0.032–0.047	0.023	−0.025–0.077
	Estradiol		0.001	−0.0004–0.003	0.002	−0.0003–0.004
	Estradiol × Sex		−0.001	−0.002–0.001	−0.001	−0.002–0.001
	Vitamin D				−0.001	−0.003–0.002
	Vitamin D × Sex				0.0001	−0.001–0.002
	n	516	360		240
	Model fit (adjusted R^2)	0.011	0.002		0.014
Y10 right-hand speed	Testosterone		0.760	−4.038–6.591	0.295	−5.174–6.419
	Testosterone × Sex		−0.939	−4.266–1.933	0.089	−3.674–3.562
	Estradiol		0.022	−0.134–0.169	−0.008	−0.179–0.155
	Estradiol × Sex		−0.002	−0.102–0.099	0.022	−0.093–0.137
	Vitamin D				−0.087	−0.212–0.055
	Vitamin D × Sex				0.055	−0.030–0.140
	n	674	461		311
	Model fit (adjusted R^2)	0.012	0.008		0.025
Y16 right-hand speed	Testosterone		−1.090	−6.056–3.958	−1.601	−7.550–4.455
	Testosterone × Sex		0.262	−2.851–3.264	0.747	−3.256–4.582
	Estradiol		−0.043	−0.169–0.070	−0.018	−0.164–0.116
	Estradiol × Sex		0.033	−0.042–0.110	0.011	−0.089–0.102
	Vitamin D				−0.168	−0.290 – −0.021
	Vitamin D × Sex				0.112	0.021–0.197
	n	516	360		240
	Model fit (adjusted R^2)	0.141	0.122		0.136
Y10 left-hand speed	Testosterone		−2.472	−6.277–1.576	−4.126	−8.522–0.444
	Testosterone × Sex		1.422	−1.192–3.966	3.151	0.102–6.344
	Estradiol		0.041	−0.064–0.142	0.024	−0.106–0.150
	Estradiol × Sex		−0.032	−0.100–0.033	−0.022	−0.113–0.060
	Vitamin D				−0.045	−0.157–0.079
	Vitamin D × Sex				0.045	−0.035–0.124
	n	675	463		312
	Model fit (adjusted R^2)	0.021	0.012		0.039
Y16 left-hand speed	Testosterone		−0.712	−5.390–3.891	−1.911	−7.323–3.435
	Testosterone × Sex		0.233	−2.526–3.125	1.179	−2.247–4.777
	Estradiol		−0.101	−0.211–0.003	−0.102	−0.226–0.011
	Estradiol × Sex		0.043	−0.022–0.111	0.031	−0.043–0.115
	Vitamin D				−0.032	−0.158–0.111
	Vitamin D × Sex				0.043	−0.045–0.130
	n	517	361		241
	Model fit (adjusted R^2)	0.117	0.130		0.142

Note. Analyses of hand preference used binary logistic regression; analyses of relative hand skill and right- and left-hand speed used multiple linear regression. All analyses used bootstrapping (10,000 resamples) and include the following covariates: delivery mode (presence [1] or absence of labour [2]), gestational age at delivery (number of days), maternal/paternal hand preference (neither parent writes with left/either hand [1] or one or both parents write with left/either hand [2]), family income (< AUD$7,000 [1], AUD$7,000-11,999 [2], AUD$12,000-23,999 [3], AUD$24,000-35,000 [4], ≥ AUD$36,000 [5]), parental education (average of maternal and paternal education: none [0] trade certificate or apprenticeship [1], professional registration [non-degree] [2], college diploma or degree [3], university degree [4]), maternal smoking during pregnancy (none [1] or any [2]), maternal alcohol consumption during pregnancy (none [1] or any [2]), maternal age at conception (years and months), birth weight (grams), age at relevant assessment (years and months), sex (female [1] or male [2]), and (Australian) season of birth (spring [September, October, November] [1], summer [December, January, February] [2], autumn [March, April, May] [3], or winter [June, July, August] [4]).

Table 4. Bootstrapped (10,000 samples) multivariate regression models with Vitamin D and Vitamin D × sex as predictors and handedness measures as outcomes.

Outcome	Predictor	β	BCa 95% CI
Y10 hand preference	Vitamin D	0.008	−0.037–0.049
	Vitamin D × Sex	0.0004	−0.026–0.027
	n	527
	Model fit (McFadden Pseudo R^2)	0.03
Y10 relative hand skill (signed)	Vitamin D	−0.002	−0.005–0.0002
	Vitamin D × Sex	0.001	−0.001–0.003
	n	516
	Model fit (adjusted R^2)	0.009
Y16 relative hand skill (signed)	Vitamin D	−0.002	−0.005–0.001
	Vitamin D × Sex	0.001	−0.001–0.003
	n	393
	Model fit (adjusted R^2)	0.005
Y10 relative hand skill (unsigned)	Vitamin D	−0.001	−0.004–0.001
	Vitamin D × Sex	0.0001	−0.002–0.002
	n	516
	Model fit (adjusted R^2)	0.015
Y16 relative hand skill (unsigned)	Vitamin D	−0.002	−0.005 – −0.001
	Vitamin D × Sex	0.001	−0.0002–0.003
	n	393
	Model fit (adjusted R^2)	0.034
Y10 right-hand speed	Vitamin D	0.0002	−0.101–0.100
	Vitamin D × Sex	0.003	−0.066–0.076
	n	520
	Model fit (adjusted R^2)	0.016
Y16 right-hand speed	Vitamin D	−0.004	−0.112–0.111
	Vitamin D × Sex	0.003	−0.076–0.077
	n	393
	Model fit (adjusted R^2)	0.147
Y10 left-hand speed	Vitamin D	0.052	−0.037–0.150
	Vitamin D × Sex	−0.018	−0.084–0.047
	n	520
	Model fit (adjusted R^2)	0.033
Y16 left-hand speed	Vitamin D	0.069	−0.030–0.177
	Vitamin D × Sex	−0.037	−0.113–0.034
	n	394
	Model fit (adjusted R^2)	0.114

Note. Analyses of hand preference used binary logistic regression; analyses of relative hand skill and right- and left-hand speed used multiple linear regression. All analyses used bootstrapping (10,000 resamples) and include the following covariates: delivery mode (presence [1] or absence of labour [2]), gestational age at delivery (number of days), maternal/paternal hand preference (neither parent writes with left/either hand [1] or one or both parents write with left/either hand [2]), family income (< AUD$7,000 [1], AUD$7,000-11,999 [2], AUD$12,000-23,999 [3], AUD$24,000-35,000 [4], ≥ AUD$36,000 [5]), parental education (average of maternal and paternal education: none [0] trade certificate or apprenticeship [1], professional registration [non-degree] [2], college diploma or degree [3], university degree [4]), maternal smoking during pregnancy (none [1] or any [2]), maternal alcohol consumption during pregnancy (none [1] or any [2]), maternal age at conception (years and months), birth weight (grams), age at relevant assessment (years and months), sex (female [1] or male [2]), and (Australian) season of birth (spring [September, October, November] [1], summer [December, January, February] [2], autumn [March, April, May] [3], or winter [June, July, August] [4]).

Table 5. Qualitative summary of results from bivariate and multivariate analyses of association between perinatal hormone concentrations and handedness outcomes measured at Y10 and Y16.

		Analysis
Outcome	Predictor	Bivariate	Multivariate Step 2	Multivariate Step 3	Multivariate Vitamin D only
Y10 hand preference	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	Null	N/A	Null	Null
Y10 relative hand skill (signed)	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	- (females)	N/A	Null	Null
Y16 relative hand skill (signed)	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	Null	N/A	- (whole sample)	Null
Y10 relative hand skill (unsigned)	Testosterone	Null	Null	Null	N/A
	Estradiol	+ (males)	Null	+ (males)	N/A
	Vitamin D	- (females)	N/A	Null	Null
Y16 relative hand skill (unsigned)	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	- (females)	N/A	Null	- (whole sample)
Y10 right-hand speed	Testosterone	- (males)	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	Null	N/A	Null	Null
Y16 right-hand speed	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	Null	N/A	+ (males)	Null
Y10 left-hand speed	Testosterone	Null	Null	+ (males)	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	+ (females)	N/A	Null	Null
Y16 left-hand speed	Testosterone	Null	Null	Null	N/A
	Estradiol	Null	Null	Null	N/A
	Vitamin D	Null	N/A	Null	Null

Note. Non-significant effects (i.e., those in which the BCa 95% CIs include zero) are indicated by “Null”; “+” and “-” indicate statistically significant positive and negative correlations, respectively, and “N/A” indicates that no relevant effect size estimate was produced by that analysis. All effects indicated to be statistically significant in the male subsample were not statistically significant in the female subsample, and vice versa.

Figure 3. Violin plots for free testosterone (a), total estradiol (b), and Vitamin D (25[OH]D) (c) stratified by Y10 hand preference (right or left).

Figure 4. Scatterplot showing a negative correlation between maternal gestational Vitamin D (25[OH]D) concentration and relative hand skill (unsigned finger tapping LI) measured at Y16.

Note. Scatterplot shows all available (unadjusted) data points (i.e., it includes those of participants who were deleted listwise in the multiple linear regression models); higher unsigned relative hand skill values indicate greater difference in speed between the right and left hands.

Data availability statement

The data that support the findings of this research are available from The Raine Study (https://rainestudy.org.au/information-for-researchers/). Restrictions apply to the availability of these data, which were used under license for this study. The R script that accompanies our analysis is available on the Open Science Framework (https://osf.io/yru2s/).