Aim: We aimed to explore the effect of lactation on development of metabolic syndrome in a prospective population-based study.
Methods: From among 4028 female participants of the Tehran Lipid and Glucose Study, aged 15–50 years, without metabolic syndrome at the initiation of the study, 925 women were randomly selected to fill out the lactation questionnaire. Women were assigned to five groups based on lactation duration including: none, 1–6 months, 7–12 months, 13–23 months and 24 months or more. Over a 9-year follow-up, metabolic syndrome was compared between these groups, before and after adjustment for possible confounding variables.
Results: Metabolic syndrome was developed in 12.1% of non-lactating women; it was 28.6%, 34.0%, 26.2% and 26.7% in women with 1–6, 7–12, 13–23 and 24 months or more of lifetime duration of lactation, respectively (P < 0.002). Adjustment for confounders revealed that women with 1–6 and 7–12 months of duration of lactation had significantly higher odds of metabolic syndrome in comparison to 24 months or more (1.4 and 1.3 times, respectively).
Conclusion: It seems that the longer duration of lactation up to 12 months may protect women against metabolic syndrome, in a dose–response manner.