Age and Height: What’s the Relationship?
As babies and children grow older, they grow taller. But as adults grow even older, they often lose height, due to declining bone density, spinal disc compression, or changes in posture that are measured as changes in height (Miall et al., 1967; Cline et al., 1989; Masunari et al., 2012; Shimizu et al., 2020). This blog post provides information about the relationship between age and height in the U.S. population in the 21st century, using data from the National Health Interview Survey (NHIS) from IPUMS NHIS.
The NHIS is a nationally representative survey that collects data on health, healthcare access, and health behaviors. IPUMS NHIS provides data from the survey from 1963 to present. In 1974, and 1976-2024 (the most recent year of data available), the survey included a height variable. Children’s height has only rarely been collected (see the universe of HEIGHT in IPUMS NHIS), so this blog post focuses on the height of adults age 18 and older. Height is respondent-reported, rather than measured directly at the time of the survey, and may be reported by someone other than the person themselves (i.e., another household member responding to the NHIS). Extreme values of height are censored in the public use data file, and individuals whose height was censored are not included in the analysis in this blog. See the codes section of HEIGHT for more detail.
Using cross-sectional survey data, it is not possible to observe within-individual changes in height over time. That is, among respondents to the National Health Interview Survey, if the average height declines in age, it does not necessarily mean that people become shorter throughout the life course; rather, it could reflect features of the survey design or methodology, mortality selection, migration selection, survey non-response, or other factors. For example, men are on average taller than women, and also have a shorter life expectancy than women. As a cohort becomes more female with age, average height will become more reflective of women’s heights than men’s. Additionally, improvements in childhood health or nutrition over several decades could mean that older cohorts are on average shorter than younger ones.
Nonetheless, analyzing cross-sectional survey data to identify the relationship between age and height can still provide insights into how the demographic characteristics of a population are expected to be associated with the physical characteristics of the population.
How does height vary by age?
The graph (Figure 1) below shows the average (mean) height in inches of U.S. adults by age, using pooled NHIS sample data from 2000-2024. The average height of adults declines in age, with the most dramatic reductions in average height occurring beginning around age 65. Since age is top-coded in the NHIS data at 85, the sharp drop in average height between ages 84 and 85 on the graph reflects the difference between mean age among 84-year-olds and mean age among adults age 85 and older. Reductions in mean height by age are modest between ages 18 and 55, amounting to a difference of less than 0.5 inches over the 37-year range.
Differences by sex
Women are shorter than men, on average. But does the relationship between age and height differ by sex? Shown in the graph below (Figure 3), average height declines as age increases for both men and women. But the rate at which average height declines over age differs by sex. For men, average height declines rather consistently and constantly with age between ages 18 and about 65. Then, after age 65, average height declines more rapidly, with a sharp dropoff after age 80. For women, average height declines more slowly at first, with more minor changes in average height between ages 18 and about 55, followed by a steeper decline after age 55.
At age 18, men’s average height is 70.15 inches, or 5 feet and 10 inches. By age 84, the average height among men is 68.87 inches, or 5 feet and 8.9 inches. This is a decline of 1.28 inches. For women, average height declines from 64.47 inches (5 feet and 4.5 inches) at age 18 to 63.09 inches (5 feet and 3.1 inches) at age 84. This is a decline of 1.38 inches. Considering that women’s average height is lower than men’s, the decline in average height between ages 18 and 84 is larger for women than men in both absolute and relative terms.
Height and mortality
The relationship between height, health, and longevity is highly debated, and differs across contexts (Deaton, 2007; Samaras, 2012; Perkins et al., 2016). Using mortality variables from the NHIS Linked Mortality File (LMF), it is possible to examine the relationship between height and age at death. The Linked Mortality File includes information on mortality status, and if deceased, year and month of death, for NHIS respondents eligible for mortality follow-up. Mortality status is recorded as of 2019. This means that in the 2000-2018 NHIS samples, which include mortality variables, deaths occurred between less than one year and 19 years after the NHIS survey was conducted.
Is height associated with age at death? For the purpose of descriptively answering this question, height is conceptualized as the difference between an individual’s height at the time of their participation in the NHIS survey, and the average height among individuals of the same age and sex. This measure is negative if the individual is shorter than average for their age and sex, and positive if the individual is taller than average.
The graph below (Figure 3) shows this measure of height plotted by age at death, among people who were deceased by December 31, 2019 and eligible for mortality follow-up. The figure includes only people who died between age 33 and 98, as sample sizes of individuals who died before age 33 or after age 98 are very small.
Notably, among NHIS respondents eligible for mortality follow-up and who died before 2020, there is not a clear relationship between height and age at death. People who die at younger ages do not appear to be relatively shorter or taller (compared to their peers defined by age and sex) than people who die at older ages.
How has the relationship between age and height changed throughout the 21st century?
Across the 21st century, there have been changes in how strongly age and height are related.
Many factors could influence the relationship between age and height, such as life expectancy, mortality selection, childhood nutrition, advances in medical technology and healthcare, and more. How has the correlation between age and height changed over time? The graph below (Figure 4) plots the correlation coefficient between age in years and height in inches over time, from 2000 through 2024. The correlation coefficient represents the relationship between a people’s age and their height. This coefficient is negative in all years, meaning that as age increases, average height decreases.
The correlation between age and height became weaker (got closer to zero) between 2000 and 2014. Then, the correlation grew stronger (became more negative) between 2015 and 2024. An important caveat underlying this trend is that the NHIS was redesigned in 2019, and data from 2018 and earlier are not comparable to data from 2019 and later. NHIS data users should acquaint themselves with the implications of the redesign for their work by reading the IPUMS NHIS page on the 2019 redesign.
