A new study reveals several factors that can contribute to weaker lungs and increase the risk of conditions like asthma, such as being born in the winter.
People born in the winter suffer asthma and other lung related problems in old age than those born in warmer months.
Being born from November to January was linked to a greater likelihood of breathing problems in adults, a study found.
Other factors that make the lungs worse in older age are having respiratory infections as a child, being born to an older mother and having a mother who smokes.
Having a pet as a child made people more likely to have stronger lungs, as did having older brothers and sisters the study found.
Cecilia Svanes, of the Department of Global Public Health and Primary Care at the University of Bergen in Norway and colleagues analysed data relating to more than 12,000 people.
They looked at data relating to the lung function of children aged 9-11 in a Europe-wide study including Britain, later followed up between the ages of 40 and 70.
Lung function was measured by spirometry, which measures how much air can breathe out in one breath.