It is already known that cigarette smoking is an environmental risk factor for MS. Second hand smoke exposure has also been linked to a greater risk for developing MS, but previous research has focused on adulthood.
To investigate whether second hand smoke may have an effect on risk during adolescent development, researchers at Copenhagen University Hospital Rigshospitalet, Denmark, looked at questionnaires answered by adults with MS and a healthy control group. To limit the effects of genetic variation, all participants chosen were born in, and had parents from, Denmark, Norway, Sweden, Iceland or the Faroe Islands.
To ascertain whether each person had been exposed to second hand smoke between the ages of 10 and 19, they were asked questions such as ‘Have you ever lived with one or more persons, who smoked indoors on a daily basis?’
For men who were active smokers after the age of 19, the risk for MS increased by roughly 59%. For males who did not become active smokers after 19, adolescent passive smoking did not significantly change MS risk. For females who were exposed but did not become active smokers after 19, the risk was around 43% higher.
Source: MS-UK 14 April 2020