The first survey on the health of Chinese singles in their late 20s and 30s, published Thursday, shows that 70 percent of respondents are unsatisfied with their lives and feel some kind of negative feelings.

Of those who reported feeling unhappy, most – 22 percent – said they were lonely. They were followed by people who felt anxiety (no percentage given).

The survey also found that 30 percent are past the age range during which it is best for a woman to have a child (25 to 30), indicating that 30 percent of the respondents are over the age of 30 and childless. Han Xiaohong, chairman of the Beijing Health Security Administration, said giving birth "too late" is unhealthy for a woman's physical and mental health, as well as the health of the baby.

Han also said that women and men have higher rates of a range of reproductive diseases during their late 20s and 30s than obesity, hypertension and fatty liver. It is unclear why she thinks it is healthier to have children during their late 20s. These diseases include gynecological diseases, breast diseases and urinary diseases.

The survey was jointly conducted by more than 40 organizations, including the Chinese Medical Doctor Association, the Beijing Health Security Association and Ciming Health Checkup Group. More than 160,570 questionnaires were counted.