BMI Patterns by Income Group

Audience question

Audience: Municipal public-health staff preparing an internal health-equity briefing.

Question: Among adults age 20-80 in the prepared classroom dataset, how does average BMI vary across NHANES cycles for one selected income group?

Setup

library(tidyverse)
library(knitr)

nhanes <- read_csv("data/nhanes_equity_v6.csv", show_col_types = FALSE)

Choose one income group

This small Quarto product uses a render-time control. Change selected_income, then render the page again. The table, title, plot, and interpretation update together.

available_income_groups <- sort(unique(na.omit(nhanes$IncomeGroup)))
selected_income <- "Low Income (<1.3)"

if (!selected_income %in% available_income_groups) {
  selected_income <- available_income_groups[1]
}

selected_income

[1] "Low Income (<1.3)"

Summary table

dashboard_summary <- nhanes |>
  filter(
    Age >= 20,
    Age <= 80,
    IncomeGroup == selected_income,
    !is.na(BMI),
    !is.na(Cycle)
  ) |>
  group_by(Cycle) |>
  summarise(
    n = n(),
    average_bmi = round(mean(BMI), 1),
    .groups = "drop"
  )

kable(
  dashboard_summary,
  col.names = c("NHANES cycle", "Records", "Average BMI (kg/m²)")
)

NHANES cycle	Records	Average BMI (kg/m²)
1999-2000	1091	28.8
2001-2002	1089	28.7
2003-2004	1183	28.6
2005-2006	1091	29.3
2007-2008	1552	29.1
2009-2010	1817	29.5
2011-2012	1724	29.4
2013-2014	1762	29.5
2015-2016	1568	30.0
2017-2018	1275	30.1
2021-2023	1141	30.4

Cycle pattern

ggplot(dashboard_summary, aes(Cycle, average_bmi, group = 1)) +
  geom_line(linewidth = 0.9, color = "#2f6f73") +
  geom_point(size = 2.4, color = "#2f6f73") +
  expand_limits(y = 0) +
  labs(
    title = paste("Average BMI for", selected_income),
    subtitle = "Adults age 20-80 in the prepared classroom dataset",
    x = "NHANES cycle",
    y = "Average BMI (kg/m²)"
  ) +
  theme_minimal(base_size = 12) +
  theme(axis.text.x = element_text(angle = 45, hjust = 1))

Average BMI across available NHANES cycles for the selected income group. The vertical scale begins at zero. Values are unweighted and descriptive.

Interpretation

For Low Income (<1.3), the cycle-specific averages range from approximately 28.6 to 30.4 kg/m² in the prepared records. Use the page to identify a pattern or question for a briefing, not to rank communities or infer a cause.

Limitation and privacy caution

This page is an unweighted, descriptive classroom summary. It does not account for the NHANES survey design, estimate the US population, or show that income causes BMI differences. Records with missing BMI, income group, cycle, or ages outside 20-80 are excluded. Only aggregate summaries are displayed; row-level records must not be uploaded to AI tools or shown in a public preview.