Seasonality and ambient temperature at time of conception in term-born individuals – influences on cardiovascular disease and obesity in adult life

Figures & data

Fig. 1 Monthly average temperatures in Helsinki, Finland in the years 1933–1945.

Table I Characteristics of the clinical study and the register cohort samples

	Register cohort sample				Clinical study sample
	Men		Women		Men		Women
n	5,846		5,391		777		901
Gestational age, weeks (mean, SD)	40.0	1.4	40.2	1.4	40.1	1.4	40.2	1.4
Birth weight, g (mean, SD)	3514.3	458.5	3370.3	433.7	3516.6	469.8	3373.8	438.1
Coronary heart disease, cases (number, %)	642	11	166	3	61	8	22	2
Cerebrovascular disease, cases (number, %)	323	6	170	3	36	5	18	2
Hypertension, cases (number, %)	1,161	20	1,019	19	186	24	188	21
BMI (kg/m^2)					27.5	4	27.7	5
Obesity (number, %)					168	22	247	27
Fat percentage (%)					23.7	6	34.0	7
Parity (number, %)
First child	2,780	48	2,504	46	372	48	419	47
Second child	1,686	29	1,627	30	209	27	287	32
Third child	785	13	703	13	111	14	117	13
Fourth or later child	595	10	557	10	83	11	78	9
SES at birth (number, %)
1=higher official	744	13	603	11	102	13	88	10
2=lower official	1,270	22	1,241	23	158	20	168	19
3=labourer	3,832	66	3,547	66	517	67	645	72
Age-at-visit (years)					61.5	2.8	61.5	3.0

Fig. 2 Hypertension risk by overall temperature quartiles of the month of conception, males and females, with 95% confidence intervals. The coldest monthly average temperatures are below the first quartile (Q1), while the warmest temperatures of our time series available are above the fourth quartile (Q4). (Q1: −16°C until −1.55°C, Q2–Q3: −1.56°C until 12.3°C, Q4: 12.31°C–21.5°C).

Table II ANOVA p-values to assess the association between season/temperature and birth weight/coronary heart disease/cerebrovascular disease in the register cohort sample

	Season	Temperature (continuous)	TempQuart (overall)	TempQuart (month)
Men
Birth weight	0.64	0.45	0.24	0.34
Coronary heart disease	0.59	0.26	0.22	0.90
Cerebrovascular disease	0.34	0.67	0.88	0.52
Hypertension	0.19	0.97	0.96	0.77
Women
Birth weight	0.74	0.78	0.98	0.20
Coronary heart disease	0.49	0.25	0.08	0.36
Cerebrovascular disease	0.16	0.65	0.77	0.79
Hypertension	0.06	0.00*	0.04*	0.42

* Statistically significant at 5% level/TempQuart: temperature quartiles.

Table III ANOVA p-values to assess the association between season/temperature and obesity variables in the clinical study sample.

	Season	Temperature (continuous)	TempQuart (overall)	TempQuart (month)
Men
BMI	0.07	0.36	0.03*	0.63
Obesity	0.58	0.30	0.14	0.54
Fat percentage	0.65	0.24	0.29	0.41
Women
BMI	0.63	0.84	0.66	0.02*
Obesity	0.41	0.82	0.87	0.02*
Fat percentage	0.77	0.75	0.77	0.03*

* Statistically significant at 5% level/TempQuart: temperature quartiles.

Significant p-values indicate that the given factor has an effect on the respective outcome.

Fig. 3 BMI by calendar month of conception, males and females, with 95% confidence intervals.