Number of children and the risk of obesity in older women
Introduction
Obesity is a significant health problem among adult women in the United States [1]. In older women, obesity has been linked to the development of type 2 diabetes mellitus [2], cardiovascular disease [3], dementia [4], urinary incontinence [5], and cancers [6], [7]. Understanding the role reproductive history plays in the development of weight gain has implications for preventing obesity in later life.
Having children is frequently cited by younger women as a cause of obesity [8]. Several mechanisms have been proposed to explain the association of number of children and obesity among women, such as insulin resistance associated with pregnancy [3], [9], [10], hormonal alterations secondary to fewer ovulatory cycles [11], increased glucocorticoid activity [12], and the excess deposit of fat tissue that accumulates, preferentially in the femoral area, during pregnancy [13]. Many of these physiological changes associated with pregnancy have been shown to persist years after childbearing [14]. In addition to these physiological changes, motherhood may also be associated with changes in diet and physical activity to accommodate living with small children.
Several investigators have found an association between reproductive history and obesity among older women [15], [16], [17], [18]. A population study from Finland found that number of children among women aged 25–84 was closely related to the prevalence of obesity independent of marital status, occupation, and smoking habits [15]. In a more recent study from Sweden, number of children was also associated with obesity among 5,464 women ages 45–73 [16]. In the Nurse's Health Study, an increase in BMI was found with increasing number of children among women aged 42–67 [17]. The Rancho Bernardo Study also found an association with number of children and obesity among women many years after childbearing [18].
Investigators have proposed socioeconomic status as a significant confounder in the number of children and obesity relationship [19]. Women with less education or of lower social class are at higher risk for obesity [20], and this effect may be related to personal habits such as excessive caloric intake as well as number of children.
We aimed to test the hypothesis that increasing number of children is associated with increasing risk for obesity among older women independent of socioeconomic status, other reproductive factors, and important health behaviors. The Cache County Study on Memory, Health, and Aging provides an excellent cohort to examine this research question.
Section snippets
Sampling frame and subjects
Cache County lies in a large mountain valley in northern Utah that extends to the Idaho border. The genetic structure of this Utah population is broadly representative of other U.S. populations of northern European ancestry. More than 90% of the elderly members of this population are members of The Church of Jesus Christ of the Latter-day Saints (LDS), and unique features of this group include low prevalence of alcohol use and smoking and high rates of parity. According to the 1990 census,
Results
The sample consisted of 2,035 women with an average age of 77 years (range from 66 to 102 years) and a mean BMI of 27. Overall, 20% of women were obese (BMI ≥ 30). The number of live births per woman ranged from 0 to 14, with a mean of four live births. Both the mean BMI as well as the proportion who were obese increased with increasing number of children (P < 0.05).
As shown in Table 1, the women who were obese were significantly younger (74.5 vs. 77.2 years), more likely to have started
Discussion
The major new finding in this study was that a dose–response relationship exists between the number of children and obesity among older women. Adjustment for sociodemographic variables, reproductive factors, and other predictors of obesity had little effect on the estimates of the odds ratios. Our study supports the observation of Sheldon (1949) that “maternal obesity”, the development of obesity in women after having a baby, especially among multiparous women, may have a long-lasting and
Acknowledgements
This work was supported by NIH Grant AG-RO1-11380 and a VA Career Development Award from Health Services Research and Development (Dr. Bastian).
Other Cache County Investigators: Kathleen A. Welsh-Bohmer, PhD, John C. S. Breitner, MD, Bonita Wyse, PhD, David C. Steffens, MD, Peter P. Zandi, PhD, Michelle C. Carlson, PhD, Brenda L. Plassman, PhD, Lawrence S. Mayer, MD, James C. Anthony, PhD, Ara S. Kachaturian, BS, Constantine Lyketsos, MD, Richard Miech, PhD, Maria C. Norton, PhD, Ingmar Skoog,
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