Secular trends in prevalence of supplement use according to baseline age groups and secular time in the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS), 1986–2006
X-axis shows the median age for each age group in each survey year. Points represent the prevalence of supplement use at the median age for the age group in each year (1986, 1990, 1994, 1998, 2002, 2006). The vertical dotted line illustrates the differences in prevalence of supplement use for participants aged 65 y in 1990, 65 y in 1998, and 65 y in 2006.