Surprises about French health emerge from long-term cohort study
Researchers looking at data collected by Constances, a long-term study of the health of over 200,000 people in France, have uncovered a trove of information about French health and habits, including evidence that the Covid-19 virus was circulating in France well before the first official recorded case.
“We collect blood and urine samples from the volunteers and we store them in liquid nitrogen for later use…and when Covid came, we took 9,000 samples and we analysed them looking for Covid serology," says Marcel Goldberg, an epidemiologist with Inserm, France’s health and medical research institute, and co-founder of Constances.
"It happens that we found some positive cases long before the first official case in France.”
France registered its first Covid patient on 24 January 2020, and then retrospectively diagnosed a case on 27 December 2019. Doctors had reported indications of Covid earlier through scans. The Constances blood samples allowed researchers to confirm the clinical observations.
They found Covid antibodies in 13 samples taken between 4 November 2019 and 30 January, suggesting the virus could have been circulating in France even before the first identified case in Wuhan, China, on 8 December 2019.
Listen to the interview with Marcel Goldberg in the Spotlight on France podcast:
Tens of thousands of volunteers
Since 2013, Constances has been recruiting tens of thousands of volunteers to undergo regular physical examinations and answer yearly questionnaires about their health and habits. Since the end of 2018, volunteers have been asked to provide blood and urine samples to be stored in a biobank for future research, like the search for Covid antibodies.
The goal is to gather as much data as possible about people’s health in France, to understand the effects of everything from diet, to the environment, to work conditions.
“We designed Constances not as a research project but as a research platform,” explains Goldberg. “It's like an observatory. It's a big scientific instrument, which is not designed to answer one specific question, but open to different research areas.”
Currently over 80 research and public health projects are examining the data.
The oldest health group project is the Framingham Heart Study, which started in 1948 and is now on its third generation of participants. Other large-scale cohorts are being followed in Germany and Sweden, for example.
Constances is the largest in France, and it has the advantage of being linked with the Social Security health system.
“It was very useful to be able to link the cohort with the national health databases,” says Goldberg. “France is unique in that we only have one system, the Social Security system. So it was a very a practical advantage.”
Though Constances started in 2013, Goldberg calls it a new cohort because it did not reach its recruitment goal until the end of 2019. Today over 220,000 people have joined the study, but it took a while because the goal was to find as diverse a sample of people as possible.
Participants were randomly selected, with a push towards diversity, explains Goldberg: “We over-sampled blue collar workers, because we know that usually they participate less. So we invited many more blue collar workers than high-level executives, and we ended up with a sample that is very balanced regarding social positions.”
People have signed on, even though Constances asks very detailed, sometimes sensitive questions about health and habits.
“We ask very sensitive questions about cannabis use, or sexual orientation, and things like that. And people really trust us."
- Marcel Goldberg
“People really answer honestly to these questions, even if it's difficult, because they trust us that the data will not be used improperly,” says Goldberg
Contributing to public health
Current projects are varied, from research into chronic diseases like diabetes or asthma, to the effects of mobile phones on health, the cognitive impacts of ageing, or the impact of sugar consumption on cognitive abilities.
The French Health Ministry is also interested in the data, which can offer insight on health policies, and where resources should be deployed. Constances researchers sent out special questionnaires dealing with Covid.
“We asked people a lot of questions about how they managed during the lockdowns, and after, their working condition, telecommuting. Also, their housing and work contracts,” says Goldberg.
In a study on the mental health effects of the pandemic, carried out with researchers in the UK, the Netherlands and Denmark, data showed that young people are suffering.
“There were some differences, but one thing in common is that the youngest are really in the worst condition,” says Goldberg. “It was the same pattern in the four countries, even if health policies are different. Young people are suffering the most, at least in terms of mental health.”
Listen to the interview with Marcel Goldberg in the Spotlight on France podcast (episode 50).
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