Each winter, there is an excess of mortality which has varying magnitude based on the latitude (distance from the Equator) of a nation. Of the excess winter mortality, respiratory mortality is the biggest single contributor (~45%) in men, though cardiovascular mortality forms a substantial share of all seasonal excess death (~37%).
In the study that these numbers are based on, the relative share of respiratory and cardiovascular mortality was flipped for women (more cardiovascular than respiratory).
Normally included inside of excess respiratory death is death due to pneumonia and influenza (P&I). Here are the weekly P&I death rates for 6 years in the USA:
The 6 Winter seasons above (peaks) show that the weekly death rate from pneumonia & influenza combined can peak out at over 3 times the median weekly rate. Explaining those peaks is paramount to getting control over public health. Excess winter death is highest in nations which undergo the greatest fluctuation in vitamin D.
But even though the changing flu numbers do not explain any more than a fourth of the changing pneumonia numbers (flu is not the predominant cause of pneumonia), vitamin D levels can and largely do explain the seasonality of death. By focusing so much on flu, health authorities set up a situation where they can intervene each year.
But, because most pneumonia deaths are not officially ascribed to flu, it is really pneumonia-from-all-causes that is driving the lion’s share of the excess respiratory mortality seen each year:
As the top graph alludes to, only about 2.74 persons out of every million were “supposed to” die each week from pneumonia and influenza — a rate associated with non-Winter weeks — but something seasonal creeps in each year and causes a steep upward spike in those deaths.
To “fix” this — i.e., to stop those Winter death spikes — perhaps the best strategy is to raise vitamin D levels. Here is a meta-analysis showing vitamin D levels significantly-associated with community-aquired pneumonia (CAP):
Other nutrients such as vitamin C and zinc are also very promising with pneumonia, but the main point is that the official “hyper-focus” on influenza as an explanation of seasonal mortality is misguided. The main driver of mortality changes in seasons is a change in one’s immune levels — mostly from a change in one’s vitamin D status.
To get seasonal excesses of death under control, the proper focus is not on opportunistic pathogens such as influenza, but on one’s own innate immunity.
Reference
[CDC weekly P&I deaths] — CDC. https://data.cdc.gov/NCHS/Weekly-Counts-of-Deaths-by-State-and-Select-Causes/3yf8-kanr
[the hyper-focus on influenza is misguided] — ASPE > CDC — Influenza Deaths: Request for Correction (RFC). https://aspe.hhs.gov/cdc-influenza-deaths-request-correction-rfc
[low vitamin D increases risk for pneumonias] — Zhou YF, Luo BA, Qin LL. The association between vitamin D deficiency and community-acquired pneumonia: A meta-analysis of observational studies. Medicine (Baltimore). 2019 Sep;98(38):e17252. doi: 10.1097/MD.0000000000017252. PMID: 31567995; PMCID: PMC6756683. https://pubmed.ncbi.nlm.nih.gov/31567995/
[For men, respiratory mortality is the greatest single contributor to excess winter mortality] — Li L, Yan ZL, Luo L, Liu W, Yang Z, Shi C, Ming BW, Yang J, Cao P, Ou CQ. Influenza-Associated Excess Mortality by Age, Sex, and Subtype/Lineage: Population-Based Time-Series Study With a Distributed-Lag Nonlinear Model. JMIR Public Health Surveill. 2023 Jan 11;9:e42530. doi: 10.2196/42530. PMID: 36630176; PMCID: PMC9878364. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9878364/
Well researched and well said. Thanks.