HIV-positive people on modern antiretroviral treatment who maintain a high CD4 T-cell count can expect to live nearly as long as their HIV-negative peers—but those with low CD4s do not fare as well.

An international team of researchers estimated life expectancy for more than 200,000 adults living with HIV in North America and Europe who had been on antiretroviral therapy for at least a year from 2015 onward. For men at age 40, life expectancy was estimated at 74.5 years for those who started treatment before 2015 and 77.0 for those who started later. For women, the corresponding estimates were 75.8 and 79.0. Life expectancy was longer for people with a CD4 count of at least 500: 79.2 years for men and 82.0 years for women who started treatment after 2015. These estimates are in line with those for the general population: about 81 years for men and about 86 years for women.

But life expectancy was around two decades shorter for people with a very low CD4 count. People with a count below 50 had about a fivefold higher risk of death than those with 500 or more CD4 cells. However, even those with less severe immune suppression—a count between 200 and 350—had about twice the risk of death as those with the highest levels.

“For people with low CD4 counts at the start of follow-up, life-expectancy estimates were substantially lower, emphasizing the continuing importance of early diagnosis and sustained treatment of HIV,” the study authors wrote.