In Reply We have read with interest the letter by Mascitelli and Goldstein regarding sex differences in body iron stores as a possible explanation for the gender gap in risk of incident myocardial infarction (MI). Serum ferritin levels have been found to correlate with traditional coronary heart disease (CHD) risk factors,1,2 but no consistent relation with the risk of CHD has been found.3 Thus, in our study4 we did not think about ferritin level as a potential confounder. An important interpretation of our results is that the risk in women seems to be unrelated to menopausal status or to any factors related to menopausal status. There appears to be no protection of being premenopausal vs postmenopausal above what can be explained by a difference in age. The declining relative risk for sex with increasing age seems to be a consequence of a more pronounced flattening of risk level changes in middle-aged men, approaching the risk level for women. This is in contrast to previous beliefs that the risk in women approximate the risk level for men at a certain age. As Mascitelli and Goldstein point out, the absolute risk of MI in women increases about a decade after normal menopausal age. However, an even steeper increase in risk is seen in men, leading to increasing sex differences in absolute risk with increasing age. It is thus difficult to explain the age incidence patterns in view of sex differences in ferritin levels. In a Danish population study5 with follow-up through 1991, standardized age incidence curves were rather parallel for men and women (log-linear scale), in apparent contrast to the age- and sex-related changes in body iron stores.
Albrektsen G, Bønaa KH. Body Iron Stores and the Gender Gap in Risk of Incident Myocardial Infarction—Reply. JAMA Intern Med. 2017;177(4):595-596. doi:10.1001/jamainternmed.2016.9675