In the heat, the first words are slow

In a context of global warming, a study on more than 12,000 children in the French cohort Elfe reveals a disturbing link. Consequently, Exposure to high temperatures during pregnancy and early childhood delays language development at 2 years.

Heat waves. Moreover, other heat waves can have deleterious effects on the progress of pregnancies, such as fetal death in utero, premature deliveries or even intrauterine growth delays. Similarly, Children’s health can also be assigned, in particular by an increase in the risk of infections and allergies. Similarly, More insidiously, global warming could also impact neurocognitive development, in particular language. In addition, This is suggesting an epidemiological study that examined the influence of ambient temperatures during pregnancy. However, the first months of life on the acquisition of vocabulary at the age of two.

Over 12. However, 000 mother-child couples of the French cohort Elfe

Part of the data in heat, first words slow this study comes from the French longitudinal study since childhood (ELFE), which follows around 18,000 children born in 2011, in mainland France.

The study population represents about two -thirds of the Elf birth cohort (n = 12. 163), after the notable exclusion of children from multiple pregnancies.

The ambient temperatures chosen are the weekly averages of the estimated day (maximum). night (minimum) and over 24 hours (averages) around the place of residence of the participating children, during the first 30 post-conceptional weeks and the first 91 postnatal weeks.

Spontaneous production of words at 2 years has been evaluated by the score obtained in the inventory of communicative. development of MacArthur-Bates (MacArthur-Bates Communicative Development Inventories [MB-CDI]) During the assessment made at the age of 2 as part of Elf.

The relationships between exposure (ambient temperatures). the answer (the scores of the MB-CDI) and with the delayed nature of the response were modeled thanks heat, first words slow to distributed delayed non-linear models (distributed delayed effects (Distributed Lag Non-linear Models [DLNMs]).

A decrease in language capacities of up to 15 %

Compared to the middle temperature of 8.3 ° C, a night temperature of 15.6 ° C (95^e percentile) at the beginning of 2^e Timester of pregnancy (weeks 14 to 19) is associated with a decrease of 3.2 % of the scores of the MB-CDI (relative risk [RR] : 0.968; 95% confidence interval [IC 95%] : 0.939 to 0.998).

After birth. relatively very hot, night and 24-hour temperatures are also associated with a decrease in MB-CDI scores, with a higher negative effect for the highest temperatures over the 24 hours. Compared to the middle temperature of 11.5 ° C, an average temperature of 21.9 ° C over 24 hours (95^e percentile) during the first seven months of life (weeks 1 to 28) is associated with a reduction of 14.8 % of heat, first words slow the scores of the MB-CDI (RR: 0.852 [0,756 à 0,960]).

Vulnerability windows

Positive effects of heat. cold on the acquisition of vocabulary were also detected during the first weeks of pregnancy and towards the middle of pregnancy. The effects of heat at the beginning of pregnancy were analyzed as methodological artefacts.

The effects of the night cold towards the end of the second trimester of pregnancy seem real. but their interpretation is not unequivocal. Indeed, the cold encourages pregnant women to stay inside the dwellings, where temperatures are higher.

The main results. concerning the effects of heat, remain significant after adjustment by three air pollutants likely to cause cognitive disorders, fine particles PM 2.5 and PM 10 and nitrogen dioxide, as well as after stratification on the sex of participants.

In total. this study shows that a very hot temperature, without being extreme, which extends during pregnancy but also after birth, can have a heat, first words slow negative effect on the number of words pronounced spontaneously at 2 years. It identifies two vulnerability windows: the start of the 2^e quarter of pregnancy and the first seven months of life.

These vulnerability windows correspond. at the cerebral level, to active periods of formation of glial cells and myelinization, synaptogenesis, formation of glial cells, and apoptosis.

More generally, these results suggest that global warming could delay language development in young children. They ask to be confirmed by other studies, but now, prevention messages could target vulnerability windows.