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August 2004, Volume 54, Issue 8

Student's Corner

Offspring Sex Ratio in Smokers

M. M. Adil  ( Medical Student Shifa College of Medicine, Islamabad. )
U. A. Khan  ( Medical Department of Physiology*,Shifa College of Medicine, Islamabad. )

Introduction

Number of developed countries including USA, Canada, Europe and many Asian countries show significant decline in male to female ratio of children during the past few decades. The reasons for the recent decline in the male to female ratio are unclear but some speculate that exposure to environmental toxins that predominantly affect male and male reproductive system could play a role. A study by Misao Fukuda showed that periconceptional smoking might be a contributing factor to a lower male to female sex ratio of offspring.1 Exposure of men to tetrachlorodibenzo-p-dioxin (TCDD) is linked to lowered male to female sex ratio in their offspring.2 It has been proposed that environmental chemicalization is responsible for the recent decline in male ratio.3 Number of industrialized countries indicates that the proportion of male born has significantly decreased.4 Reduced male births in major Italian cities are interpreted as a signal of increasing exposure to hazardous environmental conditions for male conceptions.5 Changing sex ratio in United State was seen during Styrene exposure.6,7 Stress could also reduce the sex ratio of newborns as witnessed in connection with the Kobe earthquake, which resulted in an abrupt reduction in sperm motility and a significant decline in the sex ratio.8 Use of tobacco as cigarettes and as smokeless tobacco is increasing day by day in Pakistan and becoming the global killer9, it could also be a cause for the altered sex ratio. A study was designed to see the effect of tobacco on off spring sex ratio in two major cities of Pakistan.

Methodology

To assess the ratio of male to female in the offspring of smokers and nonsmokers a cross sectional survey was conducted from April 2002 to December 2002, at Karachi, Rawalpindi, Islamabad and Kalarkahar. The tool used for the survey was a questionnaire with 27 questions. The important questions were about socio-economic status, age at the time of marriage, number of children, smoking, if yes since how long and daily consumption of cigarettes. An informed consent was obtained from all the subjects. Four hundred subjects were selected by convenient sampling. The subjects were divided into three groups on the basis of their age as under.

A= 20-35 years, B= 36-50 years and C= 51 and above
Daily consumption of cigarettes was divided into two categories, less than or equal to 14 cigarettes per day and more than or equal to 15 cigarettes per day.

Results

Table 1 shows that out of 400 subjects 56.5% were smokers and 43.5% were non-smokers. Age group B has the maximum percentage of smokers and group C has maximum percentage of non-smokers.

Table 1. Percentage of smokers and non-smokers in various age groups.
Group A B C Total
Age in years 20-35 36-50 >50
Smokers n=46 n=101 n=79 N=226
  11.50% 25.20% 19.70% 56.50%
Nonsmokers n=40 n=63 n=71 N=174
  10% 15.70% 17.70% 43.50%

Fifty eight point eight percent subjects were consuming =14 cigarettes per day and 41.2%subjects were consuming more than or equal to15 cigarettes per day. Age group B shows the maximum number of smokers in both categories (Figure).

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Table 2 shows offspring sex ratio in Pakistan. Highest ratio is seen in age group B (1.89) in non-smokers and lowest in-group A (0.55) in smokers.

Table 2. Offspring sex ratio in smokers and non-smokers.
Group A B C Total
No of offspring of n= 104 n= 26 n= 361 n= 491
non-smokers        
Male/Female (%) 54.8/45.2 65.5/34.5 61.5/38.5 60.6/39.4
Ratio 1.21 1.89 1.59 1.53
No of offspring n= 109 n= 419 n= 463 N=991
of smokers
Male/Female % 35.8/64.2 36.5/63.5 42.5/57.5 38.2/61.7
Ratio 0.55 0.57 0.73 0.61

Discussion

Tobacco was first grown in North America. The word 'nicotine' however, is of French origin, named after French Ambassador to Portugal Jean Nicot who was honored by the Queen of France when she was presented with a jeweled box containing snuff.10 Tobacco use in Pakistan is not limited to cigarette smoking. Chilum, huqqah, chewing tobacco in pan, snuff and niswar are some other common forms of intake. Experts divide tobacco use into two broad categories - smoking and smokeless tobacco. Both uses of tobacco are very common in Pakistan as established by a survey conducted by the PMRC in 1994.9 Our data show a higher percentage of smokers (56.5%) as compared to a study at Karachi, which shows 43.53 % smokers.11 This difference may be due to the reason that our study was carried out at three different cities of Pakistan and the other study was carried out only at Karachi where use of smokeless tobacco is quite common.

Normally, boys have a slight edge over girls, with almost 52 percent of all babies born worldwide being male. Couples are more likely to have a girl than a boy if either of the partners smokes heavily.1 However, the comparative number of males has been declining in several industrialized countries over the past few decades and researches suspect toxic substances may be partly to be blamed.2,3 The sex ratio at birth in most countries is between 104 and 106 males to 100 females. It fluctuates within a narrow range from time to time in some area but the general trend of the last 20 years has been downward. However, when the couples were grouped according to their smoking habits, the ratio changed.12 Some researchers suggest that sperms carrying the male sex chromosome are more vulnerable to toxic chemicals in tobacco smoke than sperm carrying the female chromosome. Such affected Y-sperm cells are less likely to fertilize or produce less viable embryos.8 Semen analyses showed that non -smoking men have healthier sperm than smoking men (in terms of sperm viability and longevity).13 The overall offspring sex ratio in nonsmokers of our study was 1.53 and 0.61 in smokers. Our results are in accordance with the results of Fakuda et al.1

It is concluded that smoking might be a contributing factor to a lower male to female sex ratio of offspring along with Estrogenic pollutants which are everywhere in our environment contaminating our food, drinking water, and air. As said by Robert O. Bonow, President of the American Heart Association."This gives male smokers another reason to kick the habit, and provides another area of emphasis and education for smoking cessation programs."14

Discussion

Tobacco was first grown in North America. The word 'nicotine' however, is of French origin, named after French Ambassador to Portugal Jean Nicot who was honored by the Queen of France when she was presented with a jeweled box containing snuff.10 Tobacco use in Pakistan is not limited to cigarette smoking. Chilum, huqqah, chewing tobacco in pan, snuff and niswar are some other common forms of intake. Experts divide tobacco use into two broad categories - smoking and smokeless tobacco. Both uses of tobacco are very common in Pakistan as established by a survey conducted by the PMRC in 1994.9 Our data show a higher percentage of smokers (56.5%) as compared to a study at Karachi, which shows 43.53 % smokers.11 This difference may be due to the reason that our study was carried out at three different cities of Pakistan and the other study was carried out only at Karachi where use of smokeless tobacco is quite common.

Normally, boys have a slight edge over girls, with almost 52 percent of all babies born worldwide being male. Couples are more likely to have a girl than a boy if either of the partners smokes heavily.1 However, the comparative number of males has been declining in several industrialized countries over the past few decades and researches suspect toxic substances may be partly to be blamed.2,3 The sex ratio at birth in most countries is between 104 and 106 males to 100 females. It fluctuates within a narrow range from time to time in some area but the general trend of the last 20 years has been downward. However, when the couples were grouped according to their smoking habits, the ratio changed.12 Some researchers suggest that sperms carrying the male sex chromosome are more vulnerable to toxic chemicals in tobacco smoke than sperm carrying the female chromosome. Such affected Y-sperm cells are less likely to fertilize or produce less viable embryos.8 Semen analyses showed that non -smoking men have healthier sperm than smoking men (in terms of sperm viability and longevity).13 The overall offspring sex ratio in nonsmokers of our study was 1.53 and 0.61 in smokers. Our results are in accordance with the results of Fakuda et al.1

It is concluded that smoking might be a contributing factor to a lower male to female sex ratio of offspring along with Estrogenic pollutants which are everywhere in our environment contaminating our food, drinking water, and air. As said by Robert O. Bonow, President of the American Heart Association."This gives male smokers another reason to kick the habit, and provides another area of emphasis and education for smoking cessation programs."14

References

1. Fukuda M, Fukuda K, Shimizu T. Parental periconceptional smoking and male : female ratio of newborn infants. Lancet 2002;359:1407-8.

2. Mocarelli P, Gerthoux PM, Ferrari E, et al. Parental concentration of dioxin and sex ratio of offspring. Lancet 2000;355:1858-63.

3. Vartiainen T, Kartovaara L, Tuomisto J. Environ Health Perspect 1999;107: 813-5.

4. Davis DL, Gottlieb MB, Stampnitzky JR. Reduced ratio of male to female births in several industrial countries: a sentinel health indicator. JAMA 1998; 279:1018-23.

5 .Astolfi P, Zonta LA. Reduced male births in major Italian cities. Hum Reprod 1999; 14: 3116-9.

6. Marcus M, Kiely J,Xu F, et al. Changing sex ratio in United Sstates 1969-1995. Fertil Steril 1998;70:270-3.

7. Kolstad HA, Bonde JP, Spano M et al. Change in semen quality and sperm chromatin structure following occupational styrene exposure. ASCLEPIDS. Int Arch Occup Environ Health 1999;72:135-41.

8 .Fukuda M, Fukuda K, Shimizu T et al. Decline in sex ratio at birth after Kobe earthquake. Hum Reprod 1998;13:2321-2.

9. Tobacco Free Initiative-Pakistan (TFI-PAK). A supplement by the network teaand volunteers .April 2001.

10. Wilbert J: Tobacco and Shamanism in South America. Available on URL: http://www.hoboes.com/html/Politics/Prohibition/Notes/Shamanism.html

11. Jaleel MA, Noreen R, Hameed A et al. Cigarette smoking survey of citizens of Karachi. Rawal Med J 2003; 28: 48-51.

12. Ross E. Study links smoking to baby's sex [04/22-2] Excerpts from: Study
Links Smoking to Baby's Sex. Available on URL: http://no-smoking.org/april02/04-22-02-2.html

13. Reuters, American Society for Reproductive Medicine, Men's Health. Available on URL: www.quitsmokinguk.com/penis_facts.htm

14. Dongfeng Gu, Xigui Wu, Xiufang Duan, et al. Reynoldsand Dale B. Glasser; Cigarettes send male sex life up in smoke. Available on URL; http://www.americanheart.org/presenter.jhtml?identifier=3009767

Abstract

Objective: To assess the ratio of male to female gender in the offspring of smokers and non-smokers.

Methods: The tool used for the survey was a questionnaire. Four hundred subjects were analyzed and were divided into three age groups.

Results: Out of 400 subjects 56.5% were smokers and 43.5% were nonsmokers. Overall offspring sex ratio in nonsmokers was 1.53 and 0.61 in smokers.

Conclusion: The smoking might be a contributing factor to a lower male to female sex ratio of offspring along with Estrogenic pollutants which are everywhere in the environment contaminating food, drinking water and air. (JPMA 54:442;2004).

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