title: Does long-term lactation protect premenopausal women against hypertension risk? A Korean women's cohort study.
abstract: BACKGROUND
  Little is known about the long-term effect of lactation on maternal cardiovascular health except for a few animal or human experimental studies. The objective of this study was to examine the effects of lactation on the incidence of hypertension in premenopausal women.
  
  
  METHODS
  The data were derived from a cohort study with 6 years follow-up (1995-2000). The cohort was composed of 177,749 Korean premenopausal women, aged 20-59, who had medical evaluations in 1992 and 1994. During the follow-up, blood pressure was measured as part of the 1996, 1998, and 2000 periodic examinations.
  
  
  RESULTS
  In multivariate Cox proportional hazard models, lactation decreased the risk of hypertension (risk ratio, 0.92; 95% confidence interval, 0.90-0.96). Compared with women who with no history of lactation, 1-6 months of lactation decreased the risk of hypertension (RR, 0.90; 95% CI, 0.87-0.93), as did 7-12 months (RR, 0.92; 95% CI, 0.87-0.98) or 13-18 months (RR, 0.93; 95% CI, 0.86-0.99). In particular, the coexistence of obesity and no lactation increased the risk of hypertension (P for interaction = 0.028).
  
  
  CONCLUSIONS
  This finding suggests that lactation may be a protective factor against hypertension among premenopausal women.
authors.affiliation: Department of Preventive Medicine and Public Health, School of Medicine, Ajou University, Yeounton-gu, Suwon 443-721, Republic of Korea. solee@ajou.ac.kr
authors.forename: Soon Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Miyong T
authors.initials: MT
authors.lastname: Kim
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Jee
authors.forename: Hannah Phil
authors.initials: HP
authors.lastname: Yang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000517:prevention & control; D015994:Incidence; D007723:Korea / Q000453:epidemiology; D007774:Lactation / Q000502:physiology*; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000503:physiopathology; D017697:Premenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk