Sexual behaviour of adolescents in Nigeria: cross sectional survey of secondary school students

Background

Nigeria has 126 million people in more than 250 ethnic groups. The major languages are English (official language), Hausa, Yoruba, Igbo, and Fulani. Most of Nigeria's 36 states adhere to English common law, though Islamic law is practised in some northern states. Since the 1999 restoration of a civilian government—after nearly 30 years of military dictatorship in the four decades since independence—Nigeria has struggled with social and political unrest. The prevalence of HIV/AIDS has increased steadily through the 1990s, maternal and infant mortality are high, and the average life expectancy is 51 years.2

Survey site

The study took place in Plateau state, in central Nigeria. Except for its capital city, Jos, the state is rural and agrarian. Its population includes 20 ethnic groups distributed across 17 local government areas and 11 school districts. English is the primary language of instruction in schools, and by the secondary level all students can read and write in basic English. Since the change of government in 1999 school schedules and student attendance have been erratic. Although conditions had improved by the time of our survey, many schools were unable to produce reliable records of student enrolment.

Participants

The study protocol was approved by Plateau state's Ministry of Education and by the institutional review board of Cincinnati Children's Hospital Medical Center. We used a clustered sampling design to select government funded secondary schools in the first stage and students in the second stage. Day schools were grouped by district, with boarding schools as a 12th group, and then the proportion of students in each group determined the number of schools that were randomly selected from that group. Although the research plan called for the random selection of 25% of day students and 12% of boarding students equally distributed by sex and age group (12-14, 15-17, and 18–21 years), many schools used convenience sampling to avoid further disruption in routine. In all, 90 307 secondary students were enrolled in 185 schools in Plateau state; the study sample consisted of 4218 students in 39 schools.

Questionnaire

A self administered, English language questionnaire comprising 96 multiple choice items was developed for the study. Most of the items were adapted from existing surveys.15–17 Nigerian adolescents and health professionals reviewed preliminary drafts of the questionnaire for comprehensibility and acceptability. The items comprised seven items on participants' sociodemographic characteristics, 12 on their school, nine on the woman identified by the participant as “mother,” nine on the man identified as “father,” 15 on family relationships, 18 on health and health care, 16 on sexual and reproductive history, and 10 on sexually transmitted infections, including HIV.

Data collection

Data collection took place from 10 March to 24 March 2000. Two teams of trained research assistants administered the survey during a 60–90 minute class. Students were told they could leave any questions blank and that their answers would remain anonymous and confidential. The research assistants distributed the questionnaires to the students, remained in the classroom during administration, and transported the completed questionnaires from the schools.

Data analysis

Teleform version 6.1 (Cardiff Software, San Diego, CA) was used to scan and transform the answer sheets into computer text, which was converted to an SAS database (SAS Institute, Cary, NC). Answer sheets were excluded from the analyses if students failed to answer yes or no to the question “Have you ever had sexual intercourse (sex with another person)?” (n=202), if they gave inconsistent answers to this question and two other questions about sexual history (n=809), or if they gave five or more invalid answers to the remaining 93 questions (n=502). Excluded and included students were compared for differences in sex, age, year level at school, place of residence, and religion. Because some students were not selected randomly and some records of enrolment were unreliable, as discussed above, we analysed the unweighted data with adjustment for design effects.

The primary outcome measure was sexual intercourse ever (sexual activity), defined as a “yes” response to the question “Have you ever had sexual intercourse (sex with another person)?” Family polygamy was defined as a “yes” response to either or both of the questions “Has your father ever had more than one wife at the same time?” and “Have you ever lived in a household where two or more women were married to one man at the same time?”

Multi-item variables (box) were adapted from measures constructed for the US national longitudinal study on adolescent health.17 These variables were coded so that higher scores represented more desirable conditions. Responses of students who answered <75% of the items in a set were excluded from analyses of the given variable. Missing responses for students who answered ≥75% were assigned the student's mean score for the set.

We used χ², Wilcoxon's rank sum, and t tests to identify associations between sexual intercourse ever (sexual activity), family polygamy, and each of the independent variables. To correct for multiple comparisons we set the significance level conservatively at P<0.01. We used logistic regression to estimate the probability of sexual activity as a function of family polygamy, adjusted for the four design effects: school group, school type (coeducational, same sex, day, boarding), and age and sex of the participant. Each variable associated with both sexual activity and family polygamy was added to the logistic regression model, and the reduction in the β coefficient for family polygamy was calculated as an estimate of the variable's mediating effect on the association between sexual activity and family polygamy.18 We used stepwise logistic regression to test the hypothesis that family polygamy is independently associated with sexual activity. The four design variables and all variables associated with sexual activity at P<0.05 were entered in the regression analysis, and those that remained significant at P<0.01 were retained.

Strengths and weaknesses of the study

The strengths of this study are its articulation of hypotheses, a sample of adequate size for testing the hypotheses, inclusion of students of both sexes, use of items from validated survey instruments, and adaptation of materials and methods to the Nigerian context. Despite the social and political turmoil throughout Nigeria during the period of data collection, participation by schools and students was uniformly high.

However, the study has weaknesses that may affect its results or interpretation. Non-random selection of participants in some schools may have resulted in a sample that did not represent the population of secondary school students in Plateau state. Furthermore, although Plateau state is broadly representative of Nigeria, it is just one of 36 states in the country. The sociodemographic profiles of excluded and included students differed, and their sexual behaviours and family structures may also have differed. Under-reporting of sexual activity by school students in Nigeria is likely, given the harsh societal reaction to behaviours that are deemed sexual offences in much of the country. Female students who are pregnant or who have had babies typically leave school. Given Nigeria's low use of contraception and high birth rates, such dropout from school is likely to skew the female student population towards students who are sexually inactive. Finally, the study collected data only from adolescents in school. In a country where less than a third of adolescents attend school, the results cannot be generalised to all adolescents nationwide.

Comparisons with other countries

Many of our findings are supported by earlier studies performed in African and Western countries. The finding that family polygamy was not associated with a particular religion is consistent with the theory that polygamy reflects a country's child mortality and its proportion of children in work more than its religious profile.19 Studies in Nigeria, South Africa, and Israel have shown that children from polygamous families have higher rates of behavioural and school problems. 10–12 19 20 Studies in North and South America have shown strong associations between adolescent sexual behaviour and interpersonal family relationships, the education, presence, and expectations of parents, and the connectedness of the adolescents to parents and school. 17 21–26

There is evidence in developed and in developing countries that acknowledging the sexual activity of adolescents and meeting their sexual health needs with targeted education and preventive care services can help reduce risky sexual behaviour and its consequences. 27 28 The sexual health needs of young people in Nigeria are high, as evidenced by the prevalence of pregnancy and sexually transmitted disease, including HIV/AIDS. By age 13 years over a quarter of the students in our study were sexually active. Among US students surveyed in the same year (1999), sexual activity by age 13 years was reported by 5.5% of white students, 20.5% of black students, and 9.2% of Hispanic students. Whereas 39% of female students in our study had had a past or current pregnancy, the rate among female high school students in the United States in the same year was 7.6%.16

Conclusions

The findings of our study can help programme planners in Nigeria tailor prevention strategies to the needs of adolescent school students but should not be generalised to adolescents who are out of school. Work that advances our understanding of the contexts of time, place, and people around adolescents in Nigeria is needed if we are to interpret international research correctly and plan interventions that are appropriate and effective.