A critical factor that plays a part in susceptibility to colds is age. A study done by the University of ichigan School of Public Health revealed particulars that seem to hold true for the general population. Infants are the most cold ridden group, averaging more than six colds in their first years. Boys have more colds than girls up to age three. After the age of three, girls are more susceptible¹ than boys, and teenage girls average three colds a year to boys’ two. The general incidence of colds continues to decline into maturity². Elderly people who are in good health have as few as one or two colds annually³. One exception is found among people in their twenties, especially women, who show a rise in cold infections, because people in this age group are most likely to have young children. Adults who delay having children until their thirties and forties experience the same sudden increase in cold infections. The study also found that economics plays an important role. As income increases, the frequency at which colds are reported in the family decreases. Families with the lowest income suffer about a third more colds than families at the upper end. Lower income generally forces people to live in more cramped⁴ quarters than those typically occupied by wealthier people, and crowding increases the opportunities for the cold virus to travel from person to person. Low income may also adversely⁵ influence diet. The degree to which poor nutrition affects susceptibility to colds is not yet clearly established, but an inadequate⁶ diet is suspected of lowering resistance generally.

年龄是人们是否易患感冒的一个重要因素。 密歇根大学公共卫生学院揭示了一些对人们普遍适用的细节。 婴儿期是最易感冒的时期，从出生到一周岁平均感冒六次。 在三周岁前，男孩比女孩感冒次数要多。 但三周岁后，女孩就更易感冒了。 十几岁的女孩年平均感冒三次，男孩则为两次。 一般说来，随着年龄的增长，感冒的次数也越来越少。 健康的老年人每年只感冒一至两次或更少。 但在二十至三十岁之间的人尤其是妇女出现了例外。 他们感冒的次数有所增加，其原因在于人们通常在这一时期带养小孩。 那些晚育至三十几岁或四十几岁才有孩子的人，在那一时期感冒次数也会突然增加。 研究还发现，经济状况与感冒息息相关。 随着收入的增加，家庭成员的感冒次数呈下降趋势。 家境贫寒的人感冒次数要比最富裕的人多三分之一。 低收入者被迫挤住在比富人居所狭小得多的空间里。 拥挤的状况为感冒病菌的传播提供了条件。低收入同样不利于合理的饮食结构。 营养不良到底对患感冒造成多大的影响目前尚不清楚，但不合理的饮食通常降低了人体的抵抗力。