Onset of the Release of Spermatozoa (Spermarche) in Chinese Male Youth

AMERICAN JOURNAL OF HUMAN BIOLOGY 12:577–587 (2000) Onset of the Release of Spermatozoa (Spermarche) in Chinese Male Youth CHENG-YE JI1* AND SEIJI OHSAWA2 1Department of Health Care Epidemiology, Beijing Medical University, Beijing, China 2Institute of Human Living Sciences, Otsuma Women’s University, Tokyo, Japan ABSTRACT Data on the prevalence of the first ejaculating emission for 83,902 Chinese boys 9 through 18 years were collected using interviews. Median spermarcheal ages (MSAs) were calculated by using the status quo data and probit analysis. Subjects consisted of 61,812 Han boys from urban and rural areas in 29 provinces, and 22,090 minority boys from 17 minority ethnic groups. Median spermarcheal ages were 14.24 years for urban Han boys and 14.85 years for rural Han boys, and ranged from 13.46 to 16.32 years for the 17 minority ethnic groups. The differences in MSAs between urban and rural Han boys in each province were significant and the correlation ,0.83 ס between MSA of urban and rural boys in each province was high (r P < 0.001). For both urban and rural Han boys, there were significant geographic variations. MSAs of boys living in north China were generally higher than those living in the south, while those living in the west were higher than those living in the east. Variation in MSA may be related to ecological conditions in the Chinese Han populations. The different estimates of spermarcheal ages with two approaches, periodical urine sample analysis vs. interview, and their effect on estimating male puberty are discussed. Am. J. Hum. Biol. 12:577–587, 2000. ©Wiley-Liss,Inc. Spermarche refers to the onset of the re- at first observed spermaturia (Baldwin, lease of spermatozoa. Because the establish- 1928; Richardson and Short, 1978; Hirsch et ment of spermatogenesis only occurs if a al., 1979; Nielsen et al., 1986a). The second boy’s reproductive system has gained suffi- approach is to investigate puberty in boys cient maturation, spermarche is regarded by questionnaires, and to estimate spermar- as a milestone in male puberty (Mu¨ ller et che on the basis of the age when first ejacu- al., 1989). On the population level, the me- lation of sperm occurs, either by masturba- dian spermarcheal age (MSA), the age when tion or spontaneously (Laron et al., 1980). 50% or more of boys have experienced their According to many authors, only the use of first ejaculation of semen, has been used to urine sample analysis may serve as an ethi- define a stage of puberty that is equivalent cal approach to determine spermarche. to menarche in girls (Hirsch et al., 1985). Studies based on questionnaires were con- However, gonadal maturation in boys is sidered inappropriate because they cannot generally be employed with normal boys for not characterized by a critical visible event, ethical reasons. Furthermore, such studies as menarche is in girls. Achieving a reliable often yield erroneous information (Nielsen and sensitive estimate of the onset of sperm et al., 1986b). production is difficult. Two approaches were used in early studies. It has been known for a long time that a postpubertal boys excrete spermatozoa in the urine; thus, the first ap- *Correspondence to: Dr. Ji Cheng-ye, Department of Health proach is to analyze the urine samples peri- Care Epidemiology, Beijing Medical University, Beijing 100083, China. E-mail: [email protected] odically for the presence of spermatozoa and Received 19 January 1999; Revision received 14 July 1999; estimate spermarche on the basis of the age Accepted 27 August 1999 ©2000Wiley-Liss,Inc. PROD #M99003R3 578 C.-Y. JI AND S. OHSAWA The estimation of spermarche has been ducted between April and June, 1991. This performed successfully in China for many study only describes geographic and ethnic years. The method used is similar to ques- variation in spermarcheal ages of Chinese tionnaires, but relies on personal interviews boys. during school health education. Based on the status quo technique, Ye et al. (1965) Han nationality reported that the MSA of Beijing boys was Han is the major Chinese nationality, 16.6 years. Since the beginning of the 1980s, which accounts for 94.2% of the total popu- a series of studies on spermarcheal age and lation. The Han are distributed nation- its relationship to other pubertal events in wide among 31 administrative districts/ boys has been reported in several large cit- provinces. In the present study, all Han ies in China, such as in Beijing (Huang, schoolboys 9 through 18 years were ran- 1987; Huang et al., 1990; Ji, 1991), Shang- domly sampled from the 29 provinces (Fig. hai (Zhang, 1982), Wuhan (Jin, 1980), and 1). The subjects were classified into two sub- Nanjing (Dai, 1981). Spermarcheal ages of groups, urban and rural. In each of these several Chinese ethnic minority groups, cities, there were 97–122 boys for each age such as the Dong, Bai, Miao, Zhuang, and group, and urban and rural division. Urban Tibetan, were reported by Tan (1982), Wei boys were resident in the provincial capi- et al. (1985), and Wu (1984). Although a tals; rural boys were resident in the country large amount of data on spermarcheal age side around the capitals. The rural boys are has been accumulated, there is a lack of re- from peasant families. The only exception cent data reflecting the overall status of was Wulumuqi city in Xinjiang, which only spermarche in Chinese boys. In addition, had 64–74 boys for each of the age sub- the statistical techniques for estimating groups. spermarcheal age were different in the pre- vious studies. To remedy this situation, a Minority ethnic groups nationwide survey on spermarcheal age in In addition to the Han, there are 55 offi- Chinese boys was included as an item in the cially recognized minority ethnic groups in 1991 Chinese National Surveillance on Stu- China. Among them, 17 were surveyed: dents Constitution and Health (Chinese Na- Mongolian, Hui, Uygur, Zhuang, Korean, tional SSCH Association, 1993). Tibetan, Miao, Buyi, Dong, Bai, Hani, Using the data of 1991 Chinese National Dai, Li, Shui, Naxi, Tu, and Salar. Their Surveillance, the present study focused on geographic distribution is shown in Figure describing differences in MSA of Chinese 2. These ethnic groups constitute 88.5% of Han boys living in diverse areas and of Chi- all the ethnic minority populations in nese minority boys in 17 ethnic groups. In China. In five of the groups (Mongolian, order to achieve a more reliable and compa- Hui, Uygur, Zhuang, and Korean), subjects rable estimation of MSA in the population, a were divided into urban and rural sub- standard procedure of inquiry was used. groups. Because of the living conditions, subjects from another 12 minority ethnic MATERIALS AND METHODS groups were only selected from rural areas. Subjects The same age definition (age at last birth- Male subjects of Han ancestry and 17 mi- day) was used in all samples, and the pre- nority ethnic groups 9 through 18 years cise age of each boy was used in questioning. were recruited in the study. They were par- Sample size was 93–144 in each of the age ticipants in the 1991 Chinese National Sur- groups. The exceptions were those of Salar veillance. This surveillance is an ongoing and Tu, which had only 62–76 subjects for national comprehensive survey conducted each age. Thus, this study is composed of every 3 years since 1985 by the Chinese Na- 83,902 subjects in total, 30,675 urban Han, tional SSCH (Survey on Students’ Constitu- 31,137 rural Han, and 22,090 minority boys. tion and Health) Association. The survey in- cludes a physical examination, screening for Selection method common diseases, physique, physiology, and Personal interviews, not the periodic col- motor ability, as well as inquiry as to men- lection of urine samples, were used to esti- archeal age in girls and spermarcheal age in mate the onset of sperm production. A pre- boys (Chinese National SSCH Association, liminary comparison of results of interviews 1993). All measures and inquiry were con- and periodic urine samples is summarized CHINESE BOYS’ SPERMARCHEAL AGE 579 Fig. 1. The geographic distribution of 29 provinces in China (except for Tibet and Taiwan). in Tables 1 and 2. First urine samples were The subjects entered the interview room collected in the morning, according to the individually. Male investigators inter- method of Hirsch et al. (1985). The results viewed each boy face-to-face, and asked showed that the positive rate was as high as whether or not he had experienced the first 79.9% when five samples of urine were ejaculation of semen. Dichotomous re- tested (a positive case means that semen sponses (yes/no) of spermarche were col- was found in the urine at least once) in lected. Because almost all schoolboys age 13 youth who gave a positive answer of ejacu- and over have some knowledge on male pu- lation at interview (Table 1). On the other bertal events from school health education, hand, only 2–10% of the youth who gave the it was not difficult to obtain responses. For negative answer of ejaculation at interview boys 12 and younger, a special course was were found to have semen in the urine conducted at the school sites prior to the (Table 2). These results are similar to those formal inquiry. The course usually took 2–3 reported by Hirsch et al. (1985), and provide hours and were conducted by trained physi- evidence of the accuracy of the personal in- cians. It covered knowledge about sexual terview method. maturation, including pubertal events, the Procedures of inquiry development of male primary and secondary sex characteristics, maturation of the testis, A thorough medical examination was ini- and the ejaculation of sperm (Ji, 1991).

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