Last week, Baltimore lost its representative, America lost a hero, and I lost my mentor and the namesake of my son, Eli.Elijah E. Cummings leaves behind an invaluable legacy as a congressman for Baltimore for more than two decades and as a champion for social justice. His passing is a call to cherish the many gifts he imparted on all those fortunate to know him, but it’s also a reminder of a painful reality facing people of colour: shorter life expectancy.Congressman Cummings died at the age of 68. This is young, but it’s not far from the average life expectancy of non-Hispanic black males (71.5), according to the latest figures from the Centres for Disease Control and Prevention. The average life expectancy for white men is five years longer, at 76.4.The congressman was well aware of this fact. In 2015, after the announced retirement of longtime senator Barbara Mikulski, he tamped down calls that he run for her seat, citing his love for Baltimore. But he also noted as a reason disparities in life expectancy for black men. That same year, a child born in the Clifton-Berea neighbourhood of Baltimore, which is 95 per cent African-American, could expect to live 67 years. Another child born just a few miles away in Cross-Country/Cheswolde, a neighbourhood that’s 73 per cent white, would live an average of 87 years.That’s a 20-year difference in life expectancy, based on one’s zip code and race.When I gave lectures on public health in Baltimore, I would show maps of disease incidence. I stopped when it became apparent that it was essentially the same map, just with different codes in the legend. The same areas with low life expectancy also had the highest rates of infant mortality, skyrocketing drug overdoses and the worst incidence of cardiovascular disease. They were also the areas hit hardest by concentrated poverty and gun violence, with the most barriers to education, housing and transportation.It is these social determinants of health that affect how long and how well people live. It is these social determinants that account for the huge disparities in Baltimore.This is the same story we see playing out in communities across the country. People of colour face more barriers to healthcare, as do low-income individuals and those living in underserved rural and urban areas. There has been progress removing these barriers: the Affordable Care Act has narrowed differences in health insurance coverage, and local programmes have reduced some neighbourhood-specific disparities. But eliminating disparities requires attention to the systemic factors that lead to ill health, including poverty and structural racism.When health is affected by so many factors, it’s often hard to know where to begin. Cummings, however, served as inspiration for what’s needed to make society more equitable.The congressman urged city leaders: “Don’t talk about what you can’t do. Do what you can do — and do it efficiently and effectively.” He was distraught that as many as 10,000 public-school students needed something as basic as eyeglasses but were not getting them. With his encouragement, we in the city’s health department started a programme for all children who needed glasses to get them, free of charge. He helped us to obtain federal grants that expanded mental health and trauma services in schools.And when the legislature was mired in a debate over a contentious needle exchange programme some 25 years ago, it was Cummings who delivered the defining speech that broke the barrier of stigma. As a result, in Baltimore, the percentage of people with HIV from intravenous drug use went from 63 per cent to 7 per cent.He also used the weight of his moral authority to stand behind other controversial public health programmes, including my blanket prescription for the opioid antidote, naloxone, which has since saved nearly 3,000 lives. When federal funding ended for a citywide collaboration to improve child health, he refused to take no for an answer. This programme ended up reducing infant mortality by nearly 40 per cent.“The cost of doing nothing isn’t nothing,” he often said, reminding us that our job must be to level the playing field. Inaction will always have a disproportionate impact on those who are the most disadvantaged. Through his example, we changed every health metric to include a disparities measure; a major point of pride for our Healthy Babies programme is that it cut the disparity between black and white infant mortality by more than 50 per cent.We still have a long way to go. Continuing the legacy of Elijah E. Cummings requires that we fulfil our destiny to fight for the world as it should be. We cannot rest as long as the currency of inequality is years of life. We cannot be content as long as where our children grow up and what colour they are determines whether they live.• Leana S. Wen is an emergency physician and a visiting professor at George Washington University Milken Institute School of Public Health. She was Baltimore health commissioner from 2015 to 2018 and chief executive of Planned Parenthood Federation of America from November 2018 until July