Sexually transmitted diseases may partly be to blame for America’s dementia epidemic, experts warn.
The latest government data shows STDs like syphilis, chlamydia, and herpes are all on the rise across the United States, impacting one in 100 Americans.
The surge, particularly in America’s nursing homes and among older adults, has largely been blamed on the increased popularity of dating and hookup apps, poor sex education, and lack of access to healthcare.
Left untreated, these can lead to issues like infertility and cancer.
However, emerging research suggests STDs may also increase the risk of dementia, a memory-robbing disorder affecting 7million Americans – a number expected to nearly double by 2060.
Researchers told DailyMail.com while ‘more research is needed,’ studies show STDs like syphilis, herpes, and human papillomavirus (HPV) may travel to the brain and lead to inflammation and neuron damage.
This can be particularly worrying for older adults who have been spreading STDs at higher rates than ever, as dementia risk doubles every five years after age 70.
The doctors urged all adults with an STD or at risk of one to either avoid sexual contact or use condoms to reduce the chance of it spreading.
STDs spread through sexual contact like kissing, oral sex, and penetrative sex. Some research has specifically linked oral sex to an increased risk of herpes (stock image)
About one in 100 US adults has an STI, including over 209,000 cases of syphilis, over 600,000 cases of gonorrhea, and over 1.6million cases of chlamydia, according to the CDC.
There were 2.4million sexually transmitted infections in 2023, which was up three percent compared to the previous year.
STDs are believed to have surged 90 percent in the past 20 years, according to the CDC.
Herpes
One of the most common STDs is herpes, distinguished by two types: HSV-1 and HSV-2.
Dr Daniel Atkinson, clinical lead at Treated.com, told DailyMail.com HSV-1 causes blisters and cold scores at the edge of your mouth – oral herpes – while HSV-2 most often causes genital herpes.
He said: ‘Both types of herpes can also be asymptomatic, which means you can easily spread it to a partner without knowing.’
Nearly half of Americans have HSV-1, while one in eight have HSV-2.
Herpes came into the spotlight earlier this month when a University of Chicago study looked at the effect HSV-1 on mice.
Herpes is most commonly transmitted from a carrier to a person without herpes by touching a cold sore, which actively produces or ‘sheds’ the virus.
However, it also leads to genital herpes by spreading through oral sex.
The study found HSV-1 hijacks a naturally occurring enzyme called heparanase (HPSE), causing it to produce high levels of inflammation.
The CDC said in November there are signs the STI epidemic is slowing after spiking 90 percent in the last 20 years
The above graph shows the rate per 100,000 people for the total number of syphilis cases recorded in the US since the 1940s. It reveals they have started to tick up again
This means when HSV-1 travels to the brain through the nose via the trigeminal or olfactory nerves, it can cause inflammation or other forms of brain damage linked to dementia.
However, the researchers caution that cases where HSV-1 infects the brain are rare, occurring in just two to four cases for every 1million people with the herpes virus.
In the experiment, mice who had HSV-1 dripped into their noses suffered memory loss, anxiety, and loss of balance – all dementia warning signs – within six months.
And in a November study of more than 1,000 people in Sweden over the course of 15 years, researchers found people who had been infected with HSV-1 were twice as likely to develop dementia than those who were not infected.
The experts suggested this could be because herpes leads to flare-ups that trigger full-body inflammation, which presses on and damages delicate tissues inside the brain.
And 2024 research from South Korea using health data from 750,000 adults found people with HSV and varicella zoster virus (VSV) – the virus that causes chickenpox and shingles – were more likely to develop dementia.
The team said this may be because the viruses can damage neurons in the brain.
Dr Atkinson said while the results of these studies seem alarming, ‘more research is needed on the links between herpes and dementia’ and most studies have only shown associations rather than a direct cause.
Syphilis
Dr Atkinson noted while the research on herpes is less firm, ‘there are definitely links between dementia and other STDs.’
Untreated syphilis, for example, may result in neurosyphilis, which attacks the brain and spinal cord and can lead to harmful inflammation.
Dr Atkinson told DailyMail.com: ‘Neurosyphilis can show up as a rapidly progressing dementia, personality change and sometimes paralysis.’
According to the CDC, syphilis surged 80 percent from 2018 to 2022, which experts have blamed on decreased condom use an drug use.
A recent study suggested just one in four US adults ages 18 to 44 used a condom the last time they had sex.
HIV and HPV
Dr Atkinson also noted people with HIV may be at a higher risk of dementia, as the virus can cause ‘cognitive and motor symptoms.’
This is called HIV dementia or HIV-associated neurocognitive disorder (HAND). This can be treated with medications to reduce the viral load of HIV and lifestyle changes like exercise.
HPV – a group of more than 200 viruses which have affected nearly every American at one point and currently affect 40 percent of Americans – has also been linked to increased dementia risks.
One 2020 study in the Journal of Dermatology using health insurance data from 16,000 patients in Taiwan found patients with genital warts from HPV were at a 49 percent increased risk of developing dementia.
However, the researchers stressed the findings only showed an association and not a direct cause.
Additionally, a 2024 study in the International Journal of Gynecological Cancer found a 1.6-fold increased risk of dementia in patients with cervical cancer.
Cervical cancer, which affects 13,800 US women per year and kills 4,300, is caused by HPV in 99 percent of cases, the CDC estimates.
The authors wrote: ‘These findings suggest [cancer-causing] HPV infections may have an association with dementia.’
They cautioned further research on this relationship is needed.
Gonorrhea
Recent research shows gonorrhea and dementia may also be related.
A 2022 study in the journal Molecular Biology and Evolution, for example, found a mutation in the gene CD33, an immune cell receptor, that protects against cognitive decline may do so due to the evolution of gonorrhea bacteria.
Gonorrhea, however, is one of the few STDs decreasing in the US, with rates dropping by seven percent between 2022 and 2023.
The takeaway
Dr Atkinson noted while more research is needed on STDs and dementia, ‘it’s important to try and avoiding spreading the infection if you have it, no matter how old you are.’
‘If you have a breakout of symptoms, avoid vaginal, anal or oral sex, or wear a condom to limit your chances of passing the infection on,’ he added.
