We have long lives in many Western nations due to two things: clean water and inexpensive pharmaceuticals. I know a lot of you complain about drug prices, but compared to living as long as say a person a 100 years ago, it's a very cheap means of longevity.
I've discussed water, but not the effects of regularly maintained purified water. It was a novel idea once, and long term studies by health experts have universally concluded that filtering and bleaching have been the most important health benefit for the populace. In a way, it's a universal medicine versus simply drinking water from wells and rivers.
“What!”, you say. “Well-water is pure.” It wasn't always. Leaching into groundwater happened from fecal sanitation issues from livestock and humans. So did chemical fertilizers. Water utilities ensured regular sources of sanitized water. Even today, well-water is filtered to ensure safety. This works as long as good practices exist, for much of rural water is from wells, but likewise high livestock populations, so as long as filter supplies last, then the well-water is clean enough to drink.
Have you considered the implication of disruptions in both over-the-counter medicines for routine ailments like fevers, diarrhea, asthma inhalers, vomiting, etc? These are just as critical, for someone can become very allergic from woodstoves, gets an infection and loses the ability to control their temperature, gets a case of stomach flu like the Norovirus, etc. Norovirus (sometimes called Norwalk) tends to go through entire households. It causes both vomiting and diarrhea. Improperly disposed of fecal matter will leach into groundwater and local water reservoirs like lakes and rivers.
Most people purchase their prescriptions on a monthly basis. Why? Usually it's a money issue. Most can purchase up to three months based upon the number of refills.
How do oral medicines work? A dose is taken, and it passes into the stomach, then it's absorbed by a network of blood vessels around the stomach. Then the active ingredient passed through general circulation and goes through the kidneys (for they are a high pressure filter) and the liver(the main-most filter). Those organs diminish their potency, but in time the drug overwhelms these organs and builds up to a therapeutic dosage in the bloodstream. This is why you must take medicine for a length of time to build up, and when you stop taking it, the level in your blood drops.
Some drugs are metabolized quickly. The level drops faster if it's not regularly taken. Those lack of those drugs, if not available, will begin to create symptoms in the patient. Things like sudden renewed high blood pressure (rebound hypertension) will happen with the sudden stopping of some heart medicines. Other drugs have their own effects.
Think about how many people in those urban and rural areas rely upon routine medicines of either kind. Many of these folks will likely be refugees. Some will stay at home and do without medicines. Both will have massively more physical activity but less water and food. Both will suffer from exposure. They'll have seasonally depressed immune systems. They may have significant return of physical and mental symptoms.
Winter is a primary time for reduced immune systems. People get exposure from being outside. They don't dress warm. Maybe they're rushing around and get less sleep. Maybe they don't eat right. They get bacterial infections. There won't be antibiotics to treat the illnesses, unless some wise administrators flex and use similar veterinary antibiotics, which are often the same compound, but with less quality control to ensure potency, efficacy (they might get more isomers), or purity. Most of the large veterinary caches of antibiotics are either in warehouses or in rural locations due to higher demand.
A reduction in medical inventory could be no saline coming in. No surgical gloves. No oxygen. Lots of shortages. Less cleaning products other than what's in inventory.
If you're a doctor, nurse, medical tech, respiratory tech, x-ray tech, etc, do you think you'll be allowed to leave the medical center to check on your family? If the administrators let you leave, how will they know you'll come back? The only reason to come back is altruism. Will that be enough to motivate a married person or a parent to come back? I don't know.
What emergency surgeries will not happen due to supply chain disruptions? What elective surgeries will not occur and may be postponed for long periods of time.
What about nursing homes, mental health centers, long term care facilities, etc do with fewer and fewer people returning to work? How will they repel sociopaths from stealing medical supplies?
Many retirees take seven or more drugs (polypharmacy) in order to cope. A very common one is hydrochlorothiazide as a diuretic to reduce blood pressure. Another is Synthroid to artificially raise metabolism. They won't have them.
Many people take medicines to cope with either high blood pressure or lower lung capacity. Both will be unable to work in their normal manner, but will have increasing amounts of work needed to survive.
A lot of people “self-medicate”. They take illegal or quasi-legal substances to cope with stress. Many are physically and psychologically addicted. The drugs often produce dopamine in their brain, and so they'll want that to occur to make them calm. It induces this, just like a gambler needs to gamble. It also makes them high.
Where will they be likely to take medicines from since dealers won't be able to get supplies or manufacture them? Probably they'll steal from retirees who use prescription pain medication. Retirees are at risk for multifactorial reasons.
Question: What will be the effect on a population's longevity in one month's time. What will be the cumulative effect from lack or minimal medical care in a year's time?