Question: In revisiting Case Study, we quoted the original journal article as reporting that "for any vertex baldness (i.e., mild, moderate, and severe combined), the age-adjusted RR was 1.4 (95% CI, 1.2 to 1.9)" (Lesko et al., 1993, p. 1000). Interpret this result. Explain in words that someone with no training in statistics would understand.

Case study: Baldness and Heart Attacks On March 8, 1993, Newsweek announced, "A really bad hair day: Researchers link baldness and heart attacks" (p. 62). The article reported that "men with typical male pattern baldness are anywhere from 30 to 300 percent more likely to suffer a heart attack than men with little or no hair loss at all." Pattern baldness is the type affecting the crown or vertex and is not the same as a receding hairline; it affects approximately one-third of middle-aged men. The report was based on an observational study conducted by researchers at Boston University School of Medicine, in which they compared 665 men who had been admitted to hospitals with their first heart attack to 772 men in the same age group (21- to 54-years-old) who had been admitted to the same hospitals for other reasons. Thirty-five hospitals were involved, all in eastern Massachusetts and Rhode Island. The study found that the percentage of men who showed some degree of pattern baldness was substantially higher for those who had had a heart attack (42%) than for those who had not (34%). Further, when they used sophisticated statistical tests to ask the question in the reverse direction, they found an increased risk of heart attack for men with any degree of pattern baldness. The analysis methods included adjustments for age and other heart attack risk factors. The increase in risk was more severe with increasing severity of baldness, after adjusting for age and other risk factors. The authors of the study speculated that there may be a third variable, perhaps a male hormone, that both increases the risk of heart attacks and leads to a propensity for baldness. With an observational study such as this, scientists can establish a connection, and they can then look for causal mechanisms in future work.