The mean age was 55 years.

平均年龄55岁。

They had a mean age of about 9 years.

他们的平均年龄是9岁。

The mean age at the initial episode was 32 years.

首次发作肉眼血尿的平均年龄为32岁。

The mean age for depression today is less than 15.

现在抑郁症人群的平均年龄小于15岁。