Our results determined that the burden of HIV/AIDS increased over 1990–2021, while there were some decreases after 2015. Men and those in their third or fourth decades had the highest incidence and burden. Among risk factors, drug use accounted for the highest burden of infection. Also, SDI and age-standardized DALY rate had an almost inverse V-shaped association. Kermanshah, Hormozgan, and Fars were the provinces with the greatest burden in both 1990 and 2021.

In this study, there were generally increasing trends of age-standardized incidence and prevalence rates over the last 32 years. However, DALY and death rates have slightly decreased in recent years, especially after 2019. The decrease in the burden of HIV/AIDS in Iran, based on the findings, might be due to the COVID-19 pandemic, which affected healthcare infrastructure and policies focused on COVID-19 prevention and control. So, it could lead to underreporting of HIV/AIDS incident cases and deaths²⁷. Accordingly, there was a significant reduction in HIV testing by 90% in 2020 in Iran²⁸. Iran showed a 654.0% increase in the age-standardized DALY rate of HIV/AIDS from 1990 to 2021. There are several explanations for this increase. Low levels of knowledge and attitude, as well as moderate-to-high stigma regarding HIV infection, can increase the risk of transmission^29,30. Also, improved diagnostic methods and access to HIV testing can lead to a high incidence and burden²⁸. To control the high burden of HIV/AIDS in Iran, educational and empowerment programs for people living with HIV, as well as prevention programs for general or key populations, are recommended^31,32.

The increasing trends for HIV/AIDS in Iran highlight the need for integrated multidisciplinary activities to control and reduce the HIV burden to meet the UNAIDS 95-95-95 focus. One of the suggested strategies is to integrate HIV and other health services, which increases HIV testing and counseling, antiretroviral therapy initiation, and improved HIV care retention³³. In Iran, changing the government’s approach to involve non-governmental organizations and civil society in policymaking may effectively decrease the HIV burden. These approaches can play instrumental roles in increasing testing rates and providing care to high-risk populations, an approach Iran could further adopt³⁴. One study showed that the main gap in the cascade of care for people living with HIV was the diagnosis, with only about one-third of total people living with HIV being diagnosed, including 37% of men aged 15 and older, 36% of women aged 15 and older, and 77% of children under 15. Even in key populations such as prisoners, case finding was insufficient, and diagnosis rates fell short of the 90-90-90 targets²¹.

The highest burden of HIV in 2021 was seen among males and those who were 35–39. It had the same sex and age pattern compared to the global burden⁵. The 25–29 and 40–44 age groups had the most considerable age-standardized DALY rates attributable to condomless sex and drug use disorders in 2019 globally, respectively^35,36. In addition, the burden of drug use disorders was higher in males, while females had a greater condomless sex attributable burden^35,36. The results were in accordance with the burden of drug use disorders in the Eastern Mediterranean Region, as males and those aged 15–49 years had the largest burden³⁷. In Iran, antiretroviral therapy coverage among total people living with HIV and men aged 15 and older showed significant differences from the targets and were 67% and 61%, respectively. In women aged 15 and older, antiretroviral therapy coverage was better at 82%, and in children under 15, 71% of those diagnosed received antiretroviral therapy. The percentage of those with viral load suppressed was much better, with over 80% in all groups²¹. The lack of sufficient care for people living with HIV in different age groups and by sex can lead to high DALY rates. These can explain the high HIV/AIDS burden in males and young adults to consider this specific population in designing preventive measures.

In both 1990 and 2021, the most significant burden was due to HIV/AIDS, resulting in other diseases or drug-susceptible tuberculosis, while drug-resistant tuberculosis (i.e., multidrug and extensively drug-resistant) had low values for age-standardized rates. Globally, among HIV/AIDS-positive individuals with tuberculosis, drug-susceptible tuberculosis ranked first in 2019, followed by multidrug and extensively drug-resistant cases³⁸. Moreover, among HIV-negative people, the age-standardized incidence rate of drug-susceptible tuberculosis (97.3 per 100,000) was higher than multidrug-resistant (5.4 per 100,000) and extensively drug-resistant tuberculosis (0.3 per 100,000) in 2021 worldwide³⁹. In Iran, the prevalence of drug-resistant cases with or without HIV/AIDS was less than 10%^13,40. These findings explain why drug-susceptible tuberculosis accounted for the largest age-standardized rates among HIV/AIDS subgroups related to tuberculosis. Despite a decrease in drug-susceptible tuberculosis cases with or without HIV/AIDS in the last three decades, there were increases in the incidence rates of drug-resistant tuberculosis^39,41. By 2040, it is projected that the burden of HIV/AIDS and drug-susceptible tuberculosis will show a downward trend globally⁴². In contrast, the incident cases of multidrug-resistant tuberculosis are anticipated to increase by 2030 in regions with low socioeconomic development⁴³. Therefore, integrating antimicrobial resistance strategies into national healthcare policies, strengthening surveillance and monitoring, and improving access to targeted treatments should be prioritized on a global scale and within Iran to address the growing challenges of drug-resistant tuberculosis and HIV/AIDS.

In accordance with the regional studies, drug use had the greatest attributable HIV/AIDS burden in Iran, followed by condomless sex and intimate partner violence⁴⁴. Controlling risk factors through multisectoral activities can reduce the HIV/AIDS burden in the future. Measures to reduce drug supply and demand, as well as harm reduction activities, might be effective for drug use disorders⁴⁵. Enhancing sexual health literacy by providing sexual education packages and developing counseling centers to reduce the stigma of sexual education are recommended approaches for the reduction of condomless sex burdens⁴⁶. Some strategies to reduce intimate partner violence among women include resilience based on spirituality, mindfulness techniques, emotionally focused couple therapy, critical thinking skills like problem-solving, decision-making, narrative exposure therapy, and conflict resolution related to domestic violence against women, in addition to self-management skills, such as anger management and marital adjustment⁴⁷.

We found an inverse V-shaped association between SDI and age-standardized DALY rate; as the age-standardized DALY rate increased with SDI up to 0.65, then it decreased. This suggests that as countries develop, the burden of HIV/AIDS initially rises due to factors such as increased life expectancy, urbanization, and risky behaviors like drug use or condomless sex. However, as countries reach higher levels of socioeconomic development, improved healthcare access, including better diagnostics, HIV testing, antiretroviral therapy, and public health campaigns, leads to a decline in the burden. Globally, low SDI countries, followed by low-middle- and middle-SDI quintiles, had the greatest age-standardized DALY rates in 2019⁵. There were also negative associations between HIV burden and SDI among the elderly in 2019 in the world⁴⁸. The differences can be due to using different data on different populations, years, and locations. Lower access to HIV care and antiretroviral therapy in countries with lower socioeconomic development can justify the higher burden in these regions. In contrast, there have been improvements in socioeconomic inequality in recent decades.

Our findings determined Kermanshah, Hormozgan, and Fars as the provinces with the greatest HIV/AIDS burden in 2021. In 2015, Hamadan (3.5) and Kermanshah (2.7) had the highest age-standardized death rates of HIV/AIDS per 100,000 population in males, and South Khorasan (2.2) and Hormozgan (1.9) had the highest among females¹⁷. Similarly, Moradi et al. showed that Kermanshah, with a DALY rate of 1.2 per 1,000 people, had the greatest burden in 2016 in Iran⁷. Among other associated factors for HIV/AIDS, Kermanshah, with an unemployment rate of > 30%, had one of the greatest unemployment in Iran⁴⁹. This highlights the role of socioeconomic determinants in the HIV/AIDS burden, emphasizing the need for targeted interventions in vulnerable populations. In addition, this underscores the necessity of addressing social and structural barriers in specific provinces of Iran to implement effective HIV/AIDS prevention and care. Future studies should further evaluate the epidemiology and the reasons for the differences in HIV burden at the subnational level to determine the optimal province-specific programs to reduce its burden.

The study has several limitations. Firstly, the estimates of the HIV/AIDS burden in Iran were affected by data quality and quantity issues. Factors such as potential misdiagnosis, miscoding, underreporting, and limited testing facilities might have affected the accuracy of results. Incomplete reporting and inconsistent data collection practices also contributed to uncertainties in the estimates. Secondly, variations in diagnostic capabilities for HIV/AIDS in Iran and between different provinces, as well as over time within Iran, may have introduced biases. This inconsistency affects the comparability of data, leading to potential inaccuracies in assessing the true burden of the disease. Thirdly, in Iran, where there are social stigmas and legal restrictions surrounding issues like drug use and condomless sex, the reliability of data on these behaviors is questionable. So, this societal and legal context can result in underreporting such behaviors and their attributable burden. Despite these limitations, it is the most updated study on the burden of HIV/AIDS in Iran and its provinces, which used the last iteration of the GBD data to estimate the burden. Furthermore, details about the risk factors, age and sex patterns, subtypes of HIV/AIDS, and its association with socioeconomic development have been assessed.