First Sister Study reinforces the importance of healthy living

March 17, 2009 — Women who maintain a healthy weight and who have lower perceived stress may be less likely to have chromosome changes associated with aging than obese and stressed women, according to a pilot study that was part of the Sister Study. The long-term Sister Study is looking at the environmental and genetic characteristics of women whose sister had breast cancer to identify factors associated with developing breast cancer. This early pilot used baseline questionnaires and samples provided by participants when they joined the Sister Study.

Two recent papers published in Cancer Epidemiology Biomarkers and Prevention looked at the length of telomeres, or the repeating DNA sequences that cap the ends of a person’s chromosomes. Telomere length is one of the many measures being looked at in the Sister Study. Telomeres protect the ends of chromosomes and buffer them against the loss of important genes during cell replication. Over the course of an individual’s lifetime, telomeres shorten, gradually becoming so short that they can trigger cell death. The papers show that factors such as obesity and perceived stress may shorten telomeres and accelerate the aging process.

The papers are the first findings coming out of the Sister Study. The Sister Study is just completing its enrollment of 50,000 women aged 35-74 to prospectively study risk factors for breast cancer.

One of the studies published this week found that women who were obese for a long time had reduced telomere length. The researchers looked at the relationship between various measures of current and past body size and telomere length in 647 women enrolled in the Sister Study. They found that women who had an overweight or obese body mass index (BMI) before or during their 30s, and maintained that status since those years, had shorter telomeres than those who became overweight or obese after their 30s.

The other paper published in February looked at the association between telomere length and the perceived stress levels of 647 women enrolled in the Sister Study, and found that similar to the obesity finding, stress can also impact telomere length. The researchers extracted DNA from blood drawn during initial enrollment to estimate telomere length, and measured levels of stress hormones in urine samples the women provided. Additionally, the researchers used a standardized scale to characterize levels of perceived stress based on answers to questions about how stressful participants perceived their life situations. In general, the researchers report that women in the Sister Study typically reported low levels of perceived stress.

The researchers also found that the effects of stress may be stronger in older women. They found that among women 55 years and older, those with higher perceived stress had 5 percent shorter telomeres than women with low stress levels. “More research is needed to determine if the shortening of telomeres in these women is related to aging or hormonal differences in the stress response, or simply represents the accumulated effects of stress across the lifespan,” said Parks. 

Source: National Institutes of Health, www.nih.gov