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Reference value of semen quality in Chinese young men☆
Contraception 65 (2002) 365–368
Original research article
Reference value of semen quality in Chinese young men夞 Wu Junqinga, Yang Qiuyinga, Tao Jianguo,a Yuan Weia, Bo Liweib, Li Yuxianc, Zhou Yumeid, Yao Kangshoue, Lu Weiqunf, Chen Lug, Gao Ershenga,* a
Shanghai Institute of Planned Parenthood Research, National Laboratory of Contraceptives and Devices Research, Shanghai, People’s Republic of China 200032 b Planned Parenthood Research Institute in Henan province, Henan, People’s Republic of China 450003 c Planned Parenthood Research Institute in Hebei province, Heibei, People’s Republic of China 200025 d Planned Parenthood Research Institute in Shanxi province, Shanxi, People’s Republic of China 030006 e Planned Parenthood Research Institute in Zhejiang province, Zhejiang, People’s Republic of China 310012 f Planned Parenthood Research Institute in Guizhou province, Guizhou, People’s Republic of China 550004 g Qingdao Institute of Planned Parenthood Research, Qingdao, People’s Republic of China 266071
Abstract The purpose of the study was to evaluate semen quality in young Chinese men and to establish reference values. Normal healthy young men from seven geographical areas were enrolled. The study showed that the mean sperm volume was 2.61 mL, and mean percent of sperm with forward progression was 59.89, while median of semen viability was 79.0%, and geometric mean of semen density was 55.45⫻106/mL. Proportion of routine semen indexes that met World Health Organization (WHO) criteria were as follows: 81.9% for semen volume, 91.1% for liquefaction time, 93.4% for viscosity, 90.8% for pH, 81.3% for sperm with forward progression, 65.3% for sperm viability, 93.8% for semen density, 98.8% for normal sperm morphology, and 89.1% for total sperm count. Participants whose sperm met all WHO standard parameters accounted for 42.3%. Because the infertility rate in China is about 10 –15%, the fifteenth percentile of semen parameters might be used as the lower limit of reference values, which may be more appropriate for young Chinese men. The fifteenth percentiles of parameters in this study were as follows: 1.5 mL for semen volume, 7.2 for pH value, 45% for proportion of sperm with forward progression, 68% for sperm viability, 30⫻106/mL for semen density, 68% for proportion of sperm with normal morphology, and 50⫻106 for total sperm count. © 2002 Elsevier Science Inc. All rights reserved. Keywords: Semen quality; Reference values
1. Introduction
2. Materials and methods
Semen analysis is one of the most valuable diagnostic methods, and it plays a critical role in andrology. Routine semen analysis plays a significant role in clinic for infertility diagnosis, particularly in developing countries. During the past few decades, decline of semen quality has been demonstrated by epidemiologic studies worldwide [1,2] and has also been shown in China [3,4]. Therefore, it is necessary to evaluate semen quality in young Chinese men and to establish reference values.
The study on semen quality was conducted between December 1998 and February 2000 in China.
夞 Support for the study was provided with funds from Shanghai Family Planning Committee. The views expressed in this manuscript, however, do not necessarily reflect those of the funding agency. * Corresponding author. Tel.: ⫹86-021-64171430; fax: ⫹86-02164046128. E-mail address: [email protected] (W. Junqing).
2.1. Volunteers and procedures Five hundred sixty-two participants enrolled in the study were healthy men between 22–30 years old. They were without reproductive problems when they underwent premarital physical examination in Maternal and Children Healthcare Centers in seven geographical areas, including Sanghai, Henan province, Zhejiang province, Shanxi province, Shandong province, Hebei province, and Guizhou province. They had lived in the locality more than 10 years, and half of them live in urban areas, and the other half in rural areas. The study included epidemiologic questionnaire inter-
0010-7824/02/$ – see front matter © 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 1 0 - 7 8 2 4 ( 0 2 ) 0 0 2 8 1 - 0
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Wu Junqing et al. / Contraception 65 (2002) 365–368
view (including demographic characteristics, behavior, living surroundings, reproductive history, toxic substance contact history, etc.), general and reproductive physical examination, and semen quality test. Two sperm samples were collected by masturbation from each participant with an interval of 2– 4 weeks, which was preceded by 3– 6 days of abstinence. Semen quality parameters included semen volume, viscosity, liquefaction time, pH value, semen density, sperm motility, percent motile sperm, sperm deformity, sperm velocity, and non-sperm cells, etc. Semen quality test was based on the recommendations set forth by World Health Organization (WHO) [5]. A technical training course was provided before the pilot study. One technician in each geographical area was trained to conduct the semen quality test so as to ensure the validity and reliability of the test. 2.2. Statistical analyses Routine semen parameters were analyzed by using SAS (6.12) software for statistics (mean and median value, range, percentiles, etc.). Logistic regressions were carried out using semen density, sperm viability, and total sperm count as dependent variables. The independent variables included age, income, occupation, behavior, reproductive history, living surroundings, and the history of toxic substance contact. A level of significant was established at .10.
3. Results The mean age of the participants was 25.6 ⫾ 2.30 years (range 22–30 years). The demographic characteristics of the participants are presented in Table 1. 3.1. Routine semen parameters There were nine routine semen quality indexes that were tested in the study. The results of routine semen quality are shown in Table 2. 1. Semen volume: Semen volume ranged from 0.5– 8.6 mL per ejaculation, among which ⬍1 mL and ⬎5 mL accounted for 1.8% and 2.1%, respectively. The mean and SD was 2.61 ⫾ 1.10 mL. 2. Liquefaction time: There were 91.1% of participants whose semen liquefied within 60 min, 4.1% over 60 min, and 4.8% incompletely liquefied. 3. Sperm viscosity: The thread length of 93.4% samples was ⱕ2 cm, and 6.6% had ⱖ2 cm. 4. pH value: There were 90.8% of participants whose pH value ranged from 6.4 –9.0 1 h after ejaculation; pH ⬎8.0 and ⬍7.2 were found in 0.7% and 8.5%, respectively. The mean and SD was 7.50 ⫾ .29. 5. Sperm with forward progression classification: Percent sperm with forward progression (including rapid
Table 1 Demographic characteristics
Age (years) 22–24 25–27 28–30 Height (cm) ⱕ165 166–175 ⬎175 Weight (kg) ⱕ55 56–65 ⬍65 Nationality Han (Majority) Minority Education ⱕJunior high school Senior high school ⱖJunior college Occupation Peasant Driver Worker CTSa Others Per capita income last year (Yuan) ⬍2000 2000– 5000– ⱖ10000 Per capita living area (m2) ⬍10 10– 20– ⱖ30 Registered permanent residence Urban Rural a
n
%
199 222 141
35.4 39.5 25.1
79 381 102
14.1 67.8 18.1
100 250 212
17.8 44.5 37.7
550 12
97.9 2.1
233 191 138
41.5 34.0 24.5
180 57 174 122 29
30.6 10.1 31.9 21.2 6.2
75 161 173 153
13.3 28.6 30.8 27.2
45 180 144 193
8.0 32.0 25.6 34.3
298 264
53.0 47.0
Cadres, teachers and scientists.
and slow forward progression) ranged from 15% to 98%, and 81.3% of samples were above 50%. The mean ⫹ SD was 59.89 ⫾ 17.11%. The mean ⫹ SD of percent samples with rapid forward progression of all samples was 36.89 ⫾ 20.19%, slow forward progression was 22.25 ⫾ 10.60%, no forward progression was 15.58 ⫾ 9.69%, and no progression was 24.35% ⫾ 13.40%. The frequency distribution of percent sperm with forward progression was basically normal. 6. Sperm viability: Sperm viability ranged from 30% to 98% 1 h after ejaculation, with the mean ⫹ SD of 77.19 ⫾ 11.87%. There were 65.3% of participants whose viable sperm was over 75%. The distribution was a bit skewed, with the median at 79%. 7. Semen density (sperm number/mL): Semen density ranged from 0 –328⫻106/mL, with the median at
Wu Junqing et al. / Contraception 65 (2002) 365–368
367
Table 2 Major indicies of semen quality Index
Mean
SD
Range
Percentile 15
25
50
75
% Coincided with WHO criteriaa
1.5 7.2 45 68 30 68 50
2.0 7.3 50 72 37 71 72
2.4 7.5 60 79 62 80 139
3.0 7.6 73 85 80 85 204
81.9 90.8 81.3 65.3 93.8 98.8 89.1
th
Semen volume (mL) pH value Sperm with forward progression (%) Sperm viability (%) Semen density (106/mL)b Percentage of normal sperm morphology (%) Total sperm count (106)b
2.61 7.50 59.89 77.19 55.45 78.23 124.06
1.10 0.29 17.11 11.87 1.46 9.15 2.39
0.5–8.6 6.4–9.0 15–98 30–98 0–328 55–99 0–1155
th
th
th
a WHO normal criteria semen volume ⱖ2 mL; proportion of sperm with forward progression (%) ⱖ50%; sperm viability (%) ⱖ75%; semen density ⱖ20 ⫻ 106/mL; percentage of normal sperm morphology ⱖ30%; total sperm count ⱖ40 ⫻ 106. b After logarithm transformation. Note: there were only 558 semen samples with results of sperm with forward progression, sperm viability (%), and percentage normal sperm morphology because of four aspermotogenic subjects.
65⫻106/mL. There were 93.8% participants whose semen density was above 20⫻106/mL 8. Semen morphology classification: Normal sperm morphology ranged from 55–99%, the mean ⫹ SD of which was 78.23 ⫾ 9.15%, headpiece defects was 8.55 ⫾ 4.93%, after-body defects was 6.21 ⫾ 4.99%, neck or mid-piece defects was 6.21 ⫾ 4.99%, and round-head was 1.64 ⫾ 2.01%. The distribution of percentage of normal sperm morphology was normal. 9. Total sperm count: Total sperm count ranged from 0 –1155⫻106/per ejaculation, with the median at 144⫻106/per ejaculation. There were 89.1% of participants whose total sperm count was equal or more than 40⫻106/per ejaculation. 3.2. Logistic regression analysis Logistic regression analysis was used to analyze the potential influential factors for semen quality. The differences were considered significant when the probability was less than .10. 3.2.1. Semen volume The results showed that the differences in semen volume were significant (p ⬍ .05) among participants living in different regions. In often wearing tight pants participants, semen volume was lower than in those not often wearing tight pants (p ⫽ .023). In cadres, teachers, and scientists, semen volume was lower than in participants with other occupations (p ⫽ .015). 3.2.2. Percent sperm with forward progression The differences in percent sperm with forward progression were significant among participants living in different regions (p ⬍ .05). There were significant differences of percent sperm with forward progression among participants with different educational levels (p ⫽ .003), with different testosterone levels (p ⫽ .039), and with different mental stress (p ⫽ .003). In those men who received at least a
college education, higher testosterone level, and higher mental stress, percent sperm with forward progression was lower than in participants who had at most only a junior high school education or had lower testosterone level and had lower mental stress. 3.2.3. Sperm viability The results showed that there were significant differences in sperm viability among participants in different regions (p ⬍ .05), with different educational levels (p ⫽ .022). In participants who had at least a college education, sperm viability was higher than in those who received at most only a junior high school education. 3.2.4. Semen density The differences in semen density were significant among participants with different education (p ⫽ .015), region (p ⬍ .05), registered permanent residence (p ⫽ .004), smoking (p ⫽ .044), alcohol intake (p ⫽ .070), wearing tight pants (p ⫽ .08), days of abstinence (p ⫽ .001), testicle volume (p ⫽ .045), and age (p ⫽ .020). In those participants who received at least a college education, lived in urban areas, had less testicle volume, did smoke, had no alcohol intake, had fewer days of abstinence, and often wore tight pants, semen density was lower than in those men who had at most a junior high school education, lived in rural areas, had larger testicle volume, did not smoke, had alcohol intake, had more days of abstinence, and did not often wear tight pants. 3.2.5. Percentage of normal sperm morphology There were statistical differences in percentage of normal sperm morphology among participants living in different regions (p ⬍ .05). In men who smoked, the percentage of normal sperm morphology was lower than in non-smoking men (p ⫽ .07). And in participants whose family used more electrical appliances, the percentage of normal sperm morphology was lower than in non-users of electrical appliances (p ⫽ .007).
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Wu Junqing et al. / Contraception 65 (2002) 365–368
3.2.6. Total sperm count The relationships between total sperm count and region (p ⬍ .05), or days of abstinence (p ⬍ .001), or testicle volume (p ⫽ .017), or age at first sexual encounter (p ⫽ .012), or smoking (p ⫽ .07) and regularly washing of external reproductive organs (p ⫽ .007) were significant. In those participants who had more days of abstinence or were older at the first sexual impulsion, total sperm count was higher than in those men who had fewer days of abstinence or were younger at first sexual encounter. Total sperm count in participants who were non-smoking and who regularly washed external reproductive organs was higher than in participants who smoked and did not regularly wash external reproductive organs.
4. Discussion Among the 512 participants, 218 men gave two semen samples with an interval of 2– 4 weeks. The differences between the two samples in semen volume, pH value, percent sperm with forward progression, sperm viability, and percentage normal sperm morphology were no more than 2%, showing that semen analyses results were reliable. The difference in semen density between the two samples was 6.18%. Because the infertility rate in China is about 10 –15%, the fifteenth percentile of semen parameters in this study might be used as the lower limit of reference values, which may be more appropriate for young Chinese men. Compared with the WHO criteria, semen density and total sperm count were slightly higher and percentage of normal sperm morphology was two times higher, whereas other parameters were slightly lower. The fifteenth percentiles of parameters in this study are as follows: 1.5/mL for semen volume, 7.2 for pH value, 45% for sperm with forward progression, 68% for sperm viability, 30⫻106/mL for semen density, 68% for percentage normal sperm morphology, and 50⫻106 for total sperm count. From the results, we can see that there are regional differences among semen parameters, which coincides with the observations made in other studies on regional difference in semen quality [6 –9]. These differences in semen quality may be attributed to different environmental exposures or lifestyle factors in the seven geographic areas. There were statistical differences in sperm with forward progression, semen density, and sperm viability among participants with different educational levels. In those participants who had at least a college education, sperm with forward progression, semen density, and sperm viability were lower than in those men who received no more than a junior high school education. There were statistical differences in semen quality between labor workers and mental
workers. Some personal behaviors might be influential factors for semen quality, such as smoking, drinking, and wearing tight pants, which is in accordance with other studies [10,11]. The results in this study indicate that semen quality could be affected by many factors. The study suggests that people should pay more attention to their behavior and living and working conditions to improve the quality of semen. However, it remains to be studied further whether such changes can account for these differences.
Acknowledgments The authors thank Mr. Wu Mingzhang and Mr. Zhang Guiyuan for their technical assistance. The data collection and semen sample collection were conducted by the Institute of Planned Parenthood Research in Henan province, Institute of Planned Parenthood Research in Zhejiang province, Institute of Planned Parenthood Research in Shanxi province, the Institute of Planned Parenthood Research in Qingdao city, Institute of Planned Parenthood Research in Heibei province and Institute of Planned Parenthood Research in Guizhou province.
References [1] Carlsen E, Giwercman A, Keiding N, et al. Evidence for decreasing quality of semen during the past 50 years. BMJ 1992;305:609 –13. [2] Irvine S, Cawood E, Richardson D, et al. Evidence of deteriorating semen quality in the United Kingdom. Birth cohort study in 577 men in Scotland over 11 years. BMJ 1996;312:467–71. [3] Zhang S, Wang H, Wang J. Changes in analysis in semen quality of fertile men in China in 1981–1996. Reprod Contracep 1999;19:27– 33. [4] Gao B, Ye, Wan Qi. Dynamic Observation of semen of 50 healthy men in Chengdu Region in a continuous year. Andriatry Mag 1988; 2:29 –32. [5] World Health Organization. WHO laboratory manual for the examination of human semen and semen-cervical mucus interaction. 3rd ed. Cambridge, UK: Cambridge University Press, 1992. [6] Jorgensen N, Andersen AG, Eustache F, et al. Regional differences in semen quality in Europe. Hum Reprod 2001;16:1012–9. [7] Auger J, Jouannet P. Evidence for regional differences of semen quality among fertile French men. Hum Reprod 1997;12:740 –5. [8] Auger J, Kunstmann JM, Czyglik F, Jouannet P. Decline in semen quality among fertile men in Paris during the past 20 years. N Engl J Med 1995;332:327– 8. [9] Fisch H, Goluboff ET. Geographic variations in sperm counts: a potential cause of bias in studies of semen quality. Fertil Steril 1996;65:1044 – 6. [10] Kidd SA, Eskenazi B, Wyrobek AJ. Effects of male age on semen quality and fertility: a review of the literature. Fertil Steril 2001;75: 237– 48. [11] Rantala ML, Koskimies AI. Semen quality of infertile couples— comparison between smokers and non-smokers. Andrologia 1987;19: 42– 6.
Original research article
Reference value of semen quality in Chinese young men夞 Wu Junqinga, Yang Qiuyinga, Tao Jianguo,a Yuan Weia, Bo Liweib, Li Yuxianc, Zhou Yumeid, Yao Kangshoue, Lu Weiqunf, Chen Lug, Gao Ershenga,* a
Shanghai Institute of Planned Parenthood Research, National Laboratory of Contraceptives and Devices Research, Shanghai, People’s Republic of China 200032 b Planned Parenthood Research Institute in Henan province, Henan, People’s Republic of China 450003 c Planned Parenthood Research Institute in Hebei province, Heibei, People’s Republic of China 200025 d Planned Parenthood Research Institute in Shanxi province, Shanxi, People’s Republic of China 030006 e Planned Parenthood Research Institute in Zhejiang province, Zhejiang, People’s Republic of China 310012 f Planned Parenthood Research Institute in Guizhou province, Guizhou, People’s Republic of China 550004 g Qingdao Institute of Planned Parenthood Research, Qingdao, People’s Republic of China 266071
Abstract The purpose of the study was to evaluate semen quality in young Chinese men and to establish reference values. Normal healthy young men from seven geographical areas were enrolled. The study showed that the mean sperm volume was 2.61 mL, and mean percent of sperm with forward progression was 59.89, while median of semen viability was 79.0%, and geometric mean of semen density was 55.45⫻106/mL. Proportion of routine semen indexes that met World Health Organization (WHO) criteria were as follows: 81.9% for semen volume, 91.1% for liquefaction time, 93.4% for viscosity, 90.8% for pH, 81.3% for sperm with forward progression, 65.3% for sperm viability, 93.8% for semen density, 98.8% for normal sperm morphology, and 89.1% for total sperm count. Participants whose sperm met all WHO standard parameters accounted for 42.3%. Because the infertility rate in China is about 10 –15%, the fifteenth percentile of semen parameters might be used as the lower limit of reference values, which may be more appropriate for young Chinese men. The fifteenth percentiles of parameters in this study were as follows: 1.5 mL for semen volume, 7.2 for pH value, 45% for proportion of sperm with forward progression, 68% for sperm viability, 30⫻106/mL for semen density, 68% for proportion of sperm with normal morphology, and 50⫻106 for total sperm count. © 2002 Elsevier Science Inc. All rights reserved. Keywords: Semen quality; Reference values
1. Introduction
2. Materials and methods
Semen analysis is one of the most valuable diagnostic methods, and it plays a critical role in andrology. Routine semen analysis plays a significant role in clinic for infertility diagnosis, particularly in developing countries. During the past few decades, decline of semen quality has been demonstrated by epidemiologic studies worldwide [1,2] and has also been shown in China [3,4]. Therefore, it is necessary to evaluate semen quality in young Chinese men and to establish reference values.
The study on semen quality was conducted between December 1998 and February 2000 in China.
夞 Support for the study was provided with funds from Shanghai Family Planning Committee. The views expressed in this manuscript, however, do not necessarily reflect those of the funding agency. * Corresponding author. Tel.: ⫹86-021-64171430; fax: ⫹86-02164046128. E-mail address: [email protected] (W. Junqing).
2.1. Volunteers and procedures Five hundred sixty-two participants enrolled in the study were healthy men between 22–30 years old. They were without reproductive problems when they underwent premarital physical examination in Maternal and Children Healthcare Centers in seven geographical areas, including Sanghai, Henan province, Zhejiang province, Shanxi province, Shandong province, Hebei province, and Guizhou province. They had lived in the locality more than 10 years, and half of them live in urban areas, and the other half in rural areas. The study included epidemiologic questionnaire inter-
0010-7824/02/$ – see front matter © 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 1 0 - 7 8 2 4 ( 0 2 ) 0 0 2 8 1 - 0
366
Wu Junqing et al. / Contraception 65 (2002) 365–368
view (including demographic characteristics, behavior, living surroundings, reproductive history, toxic substance contact history, etc.), general and reproductive physical examination, and semen quality test. Two sperm samples were collected by masturbation from each participant with an interval of 2– 4 weeks, which was preceded by 3– 6 days of abstinence. Semen quality parameters included semen volume, viscosity, liquefaction time, pH value, semen density, sperm motility, percent motile sperm, sperm deformity, sperm velocity, and non-sperm cells, etc. Semen quality test was based on the recommendations set forth by World Health Organization (WHO) [5]. A technical training course was provided before the pilot study. One technician in each geographical area was trained to conduct the semen quality test so as to ensure the validity and reliability of the test. 2.2. Statistical analyses Routine semen parameters were analyzed by using SAS (6.12) software for statistics (mean and median value, range, percentiles, etc.). Logistic regressions were carried out using semen density, sperm viability, and total sperm count as dependent variables. The independent variables included age, income, occupation, behavior, reproductive history, living surroundings, and the history of toxic substance contact. A level of significant was established at .10.
3. Results The mean age of the participants was 25.6 ⫾ 2.30 years (range 22–30 years). The demographic characteristics of the participants are presented in Table 1. 3.1. Routine semen parameters There were nine routine semen quality indexes that were tested in the study. The results of routine semen quality are shown in Table 2. 1. Semen volume: Semen volume ranged from 0.5– 8.6 mL per ejaculation, among which ⬍1 mL and ⬎5 mL accounted for 1.8% and 2.1%, respectively. The mean and SD was 2.61 ⫾ 1.10 mL. 2. Liquefaction time: There were 91.1% of participants whose semen liquefied within 60 min, 4.1% over 60 min, and 4.8% incompletely liquefied. 3. Sperm viscosity: The thread length of 93.4% samples was ⱕ2 cm, and 6.6% had ⱖ2 cm. 4. pH value: There were 90.8% of participants whose pH value ranged from 6.4 –9.0 1 h after ejaculation; pH ⬎8.0 and ⬍7.2 were found in 0.7% and 8.5%, respectively. The mean and SD was 7.50 ⫾ .29. 5. Sperm with forward progression classification: Percent sperm with forward progression (including rapid
Table 1 Demographic characteristics
Age (years) 22–24 25–27 28–30 Height (cm) ⱕ165 166–175 ⬎175 Weight (kg) ⱕ55 56–65 ⬍65 Nationality Han (Majority) Minority Education ⱕJunior high school Senior high school ⱖJunior college Occupation Peasant Driver Worker CTSa Others Per capita income last year (Yuan) ⬍2000 2000– 5000– ⱖ10000 Per capita living area (m2) ⬍10 10– 20– ⱖ30 Registered permanent residence Urban Rural a
n
%
199 222 141
35.4 39.5 25.1
79 381 102
14.1 67.8 18.1
100 250 212
17.8 44.5 37.7
550 12
97.9 2.1
233 191 138
41.5 34.0 24.5
180 57 174 122 29
30.6 10.1 31.9 21.2 6.2
75 161 173 153
13.3 28.6 30.8 27.2
45 180 144 193
8.0 32.0 25.6 34.3
298 264
53.0 47.0
Cadres, teachers and scientists.
and slow forward progression) ranged from 15% to 98%, and 81.3% of samples were above 50%. The mean ⫹ SD was 59.89 ⫾ 17.11%. The mean ⫹ SD of percent samples with rapid forward progression of all samples was 36.89 ⫾ 20.19%, slow forward progression was 22.25 ⫾ 10.60%, no forward progression was 15.58 ⫾ 9.69%, and no progression was 24.35% ⫾ 13.40%. The frequency distribution of percent sperm with forward progression was basically normal. 6. Sperm viability: Sperm viability ranged from 30% to 98% 1 h after ejaculation, with the mean ⫹ SD of 77.19 ⫾ 11.87%. There were 65.3% of participants whose viable sperm was over 75%. The distribution was a bit skewed, with the median at 79%. 7. Semen density (sperm number/mL): Semen density ranged from 0 –328⫻106/mL, with the median at
Wu Junqing et al. / Contraception 65 (2002) 365–368
367
Table 2 Major indicies of semen quality Index
Mean
SD
Range
Percentile 15
25
50
75
% Coincided with WHO criteriaa
1.5 7.2 45 68 30 68 50
2.0 7.3 50 72 37 71 72
2.4 7.5 60 79 62 80 139
3.0 7.6 73 85 80 85 204
81.9 90.8 81.3 65.3 93.8 98.8 89.1
th
Semen volume (mL) pH value Sperm with forward progression (%) Sperm viability (%) Semen density (106/mL)b Percentage of normal sperm morphology (%) Total sperm count (106)b
2.61 7.50 59.89 77.19 55.45 78.23 124.06
1.10 0.29 17.11 11.87 1.46 9.15 2.39
0.5–8.6 6.4–9.0 15–98 30–98 0–328 55–99 0–1155
th
th
th
a WHO normal criteria semen volume ⱖ2 mL; proportion of sperm with forward progression (%) ⱖ50%; sperm viability (%) ⱖ75%; semen density ⱖ20 ⫻ 106/mL; percentage of normal sperm morphology ⱖ30%; total sperm count ⱖ40 ⫻ 106. b After logarithm transformation. Note: there were only 558 semen samples with results of sperm with forward progression, sperm viability (%), and percentage normal sperm morphology because of four aspermotogenic subjects.
65⫻106/mL. There were 93.8% participants whose semen density was above 20⫻106/mL 8. Semen morphology classification: Normal sperm morphology ranged from 55–99%, the mean ⫹ SD of which was 78.23 ⫾ 9.15%, headpiece defects was 8.55 ⫾ 4.93%, after-body defects was 6.21 ⫾ 4.99%, neck or mid-piece defects was 6.21 ⫾ 4.99%, and round-head was 1.64 ⫾ 2.01%. The distribution of percentage of normal sperm morphology was normal. 9. Total sperm count: Total sperm count ranged from 0 –1155⫻106/per ejaculation, with the median at 144⫻106/per ejaculation. There were 89.1% of participants whose total sperm count was equal or more than 40⫻106/per ejaculation. 3.2. Logistic regression analysis Logistic regression analysis was used to analyze the potential influential factors for semen quality. The differences were considered significant when the probability was less than .10. 3.2.1. Semen volume The results showed that the differences in semen volume were significant (p ⬍ .05) among participants living in different regions. In often wearing tight pants participants, semen volume was lower than in those not often wearing tight pants (p ⫽ .023). In cadres, teachers, and scientists, semen volume was lower than in participants with other occupations (p ⫽ .015). 3.2.2. Percent sperm with forward progression The differences in percent sperm with forward progression were significant among participants living in different regions (p ⬍ .05). There were significant differences of percent sperm with forward progression among participants with different educational levels (p ⫽ .003), with different testosterone levels (p ⫽ .039), and with different mental stress (p ⫽ .003). In those men who received at least a
college education, higher testosterone level, and higher mental stress, percent sperm with forward progression was lower than in participants who had at most only a junior high school education or had lower testosterone level and had lower mental stress. 3.2.3. Sperm viability The results showed that there were significant differences in sperm viability among participants in different regions (p ⬍ .05), with different educational levels (p ⫽ .022). In participants who had at least a college education, sperm viability was higher than in those who received at most only a junior high school education. 3.2.4. Semen density The differences in semen density were significant among participants with different education (p ⫽ .015), region (p ⬍ .05), registered permanent residence (p ⫽ .004), smoking (p ⫽ .044), alcohol intake (p ⫽ .070), wearing tight pants (p ⫽ .08), days of abstinence (p ⫽ .001), testicle volume (p ⫽ .045), and age (p ⫽ .020). In those participants who received at least a college education, lived in urban areas, had less testicle volume, did smoke, had no alcohol intake, had fewer days of abstinence, and often wore tight pants, semen density was lower than in those men who had at most a junior high school education, lived in rural areas, had larger testicle volume, did not smoke, had alcohol intake, had more days of abstinence, and did not often wear tight pants. 3.2.5. Percentage of normal sperm morphology There were statistical differences in percentage of normal sperm morphology among participants living in different regions (p ⬍ .05). In men who smoked, the percentage of normal sperm morphology was lower than in non-smoking men (p ⫽ .07). And in participants whose family used more electrical appliances, the percentage of normal sperm morphology was lower than in non-users of electrical appliances (p ⫽ .007).
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Wu Junqing et al. / Contraception 65 (2002) 365–368
3.2.6. Total sperm count The relationships between total sperm count and region (p ⬍ .05), or days of abstinence (p ⬍ .001), or testicle volume (p ⫽ .017), or age at first sexual encounter (p ⫽ .012), or smoking (p ⫽ .07) and regularly washing of external reproductive organs (p ⫽ .007) were significant. In those participants who had more days of abstinence or were older at the first sexual impulsion, total sperm count was higher than in those men who had fewer days of abstinence or were younger at first sexual encounter. Total sperm count in participants who were non-smoking and who regularly washed external reproductive organs was higher than in participants who smoked and did not regularly wash external reproductive organs.
4. Discussion Among the 512 participants, 218 men gave two semen samples with an interval of 2– 4 weeks. The differences between the two samples in semen volume, pH value, percent sperm with forward progression, sperm viability, and percentage normal sperm morphology were no more than 2%, showing that semen analyses results were reliable. The difference in semen density between the two samples was 6.18%. Because the infertility rate in China is about 10 –15%, the fifteenth percentile of semen parameters in this study might be used as the lower limit of reference values, which may be more appropriate for young Chinese men. Compared with the WHO criteria, semen density and total sperm count were slightly higher and percentage of normal sperm morphology was two times higher, whereas other parameters were slightly lower. The fifteenth percentiles of parameters in this study are as follows: 1.5/mL for semen volume, 7.2 for pH value, 45% for sperm with forward progression, 68% for sperm viability, 30⫻106/mL for semen density, 68% for percentage normal sperm morphology, and 50⫻106 for total sperm count. From the results, we can see that there are regional differences among semen parameters, which coincides with the observations made in other studies on regional difference in semen quality [6 –9]. These differences in semen quality may be attributed to different environmental exposures or lifestyle factors in the seven geographic areas. There were statistical differences in sperm with forward progression, semen density, and sperm viability among participants with different educational levels. In those participants who had at least a college education, sperm with forward progression, semen density, and sperm viability were lower than in those men who received no more than a junior high school education. There were statistical differences in semen quality between labor workers and mental
workers. Some personal behaviors might be influential factors for semen quality, such as smoking, drinking, and wearing tight pants, which is in accordance with other studies [10,11]. The results in this study indicate that semen quality could be affected by many factors. The study suggests that people should pay more attention to their behavior and living and working conditions to improve the quality of semen. However, it remains to be studied further whether such changes can account for these differences.
Acknowledgments The authors thank Mr. Wu Mingzhang and Mr. Zhang Guiyuan for their technical assistance. The data collection and semen sample collection were conducted by the Institute of Planned Parenthood Research in Henan province, Institute of Planned Parenthood Research in Zhejiang province, Institute of Planned Parenthood Research in Shanxi province, the Institute of Planned Parenthood Research in Qingdao city, Institute of Planned Parenthood Research in Heibei province and Institute of Planned Parenthood Research in Guizhou province.
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