Later puberty onset among chronically undernourished adolescents living in a Karachi slum, Pakistan

Aim To assess factors associated with the timing of puberty onset (Tanner Stage Breast 2/Genital 2) among adolescents living in an urban slum in Karachi, Pakistan. Methods Girls enrolled at 8-10 years (n = 1009) and boys 9-11 years (n = 863) were followed every 6 months from 2006 to 2010. Parametric survival analysis for interval-censored data was used to estimate median age at puberty onset and assess the association between exposures and timing of puberty onset. Results The overall median age at Tanner Stage Breast 2 (AAB2) was 10.1 years (95% CI: 10.1; 10.5), and the median age at Tanner Stage Genital 2 (AAG2) was 10.1 years (95% CI: 10.1; 10.6). Stunting delayed AAB2 1 year and AAG2 about 6 months when compared to non-stunted peers. In the multivariable model, after adjusting for age at enrolment, stunting, thinness and vitamin A deficiency (VAD) were significantly associated with delayed AAB2, while stunting and anaemia were significantly associated with delayed AAG2. Conclusion Among adolescents living in the Karachi slum, stunting and highly prevalent anaemia delayed AAG2, while stunting, thinness and VAD delayed AAG2. Parental and household factors were not significantly associated with the timing of puberty onset.