Dr. Carol H. Gold, Penn State research scientist and study leader, says, "In our study of older brother/sister twin pairs, we found that using a three-level severity of illness scale paints a much richer picture of gender differences in health than the usual life threatening vs. non-life threatening categories usually reported. With this more complex approach we found an important category of illnesses and conditions with no gender differences –the somewhat life-threatening health problems – and this category includes the largest number of health problems of all.
"This category is a very critical one to examine when trying to disentangle the complexity of gender differences and similarities in health and aging. Perhaps it is also a reminder to focus not only on gender differences," she adds.
Gold explains that the study is the first to employ a matched sample of older brother/sister twin pairs to examine gender differences in health during aging. The team's analysis found that, on average, both brothers and sisters had the same number of illnesses, about 1.5, from the somewhat life-threatening category. The numbers of conditions that the brothers and sister had from the other, smaller, categories differed. For example, on average, the sisters had 2 not-at-all life threatening conditions while the brothers had 1.6. The sisters had about 0.4 very life-threatening conditions and the brothers had 0.7. Overall, in all categories, the sisters had about four conditions and the brothers about 3, on average.
The study is detailed in a paper, "Gender and Health: A Study of Older Unlike-Sex Twins," published in the current (May) issue of the Journal of Gerontology: Social Sciences. The authors are Gold, who holds joint appointments at the Department of Biobehavioral Health at Penn State and the Institute of Gerontology at the University College of Health Sciences in Jonkoping, Sweden; Dr. Bo Malmberg, who also holds joint appointments at Penn State and the Institute of Gerontology, Jonkoping Sweden; Dr. Gerald E. McClearn, the Evan Pugh Professor of Health and Human Development at Penn State; Dr. Nancy Pedersen, Department of Medical Epidemiology, The Karolinska Institute, Stockholm, Sweden and the Department of Psychology, University of Southern California; and Dr. Stig Berg, who holds joint appointments at Penn State and the Institute of Gerontology, Jonkoping Sweden.
The study team sent mail surveys to all pairs of brother/sister twins living in Sweden who had been born between 1906 and 1925. The twins were identified through the Swedish Twin Registry. A total of 605 pairs of twins responded, about 54 percent of the total. The average age of the participants was 74.2 years.
The twins were asked to report their illnesses by responding yes or no to a query about whether they had each of 48 health problems and conditions. They were also asked to indicate on a checklist if they had any of 30 symptoms and to answer four questions: 1) How would you rate your health? 2) How would your rate your health compared to others your age? 3) Does your health prevent you from doing what you would like to do? and 4) How would you compare your health to that of three years ago?
Gold notes that having a matched sample of older, brother/sister twin pairs enabled the researchers to reduce the effects of gender differences in survival and focus specifically on gender differences in health.
"By using unlike-sex twins, the women are selected to the same extent as the men with regard to genetic (apart from sex-linked genes) and early environmental influence," she adds. "We contend that this approach provides a better estimate of gender differences than conventional population studies that cannot control as well for these background characteristics."
As have other researchers, they found no gender differences in self-rated health. "Even though men had more life threatening conditions than women, there were no gender differences in the way the respondents described their health," the Penn State researcher says. "For example, men who had hypertension and had experienced a heart attack rated their health ‘Good' as often as women who had arthritis and back problems."
The researchers write: "Women reported more total health problems, not life-threatening health conditions, somewhat life-threatening cardiovascular conditions and physical and psychological symptoms. Men had more very life-threatening health conditions and cardiovascular conditions. No gender differences were found in the number of somewhat life-threatening health conditions, total cardiovascular conditions or self-rated health."
The MacArthur Foundation Research Network on Successful Aging, the Axel and Margaret Ax:son Johnson Foundation, The Swedish Council for Social Research and the Swedish Foundation for Health Care Sciences and Allergy Research supported the project.