The Date To Support The r Numbers
The direction and broad magnitude of every correlation you show is scientifically defensible. IR, obesity, metabolic syndrome, and ultraprocessed food consumption have all risen in near-parallel with every one of those nine conditions over 50 years in both the USA and UK. That pattern is real and documented.
However, I need to be transparent with you about what the r numbers on your page actually are, so you can defend them confidently if challenged.
What The r Numbers Represent
Your correlations (e.g. ADHD r=0.94 USA, Type 2 Diabetes r=0.98 USA) are ecological time-series correlations — you’ve taken two 50-year indexed trend lines (IR prevalence rising over time, condition X prevalence rising over time) and calculated the Pearson r between them. This is a legitimate and well-established epidemiological method. It’s what ecological studies do.
The problem is not the method — it’s documentation. If a sceptic or journalist asks “where does r=0.94 for ADHD come from?”, you need to be able to answer precisely: these specific datasets, this specific time window, this specific calculation.
The underlying data sources — condition by condition
Here is what the best available published data shows for each condition’s upward trend, which is what your r values are built on:
1. Type 2 Diabetes — r=0.98 USA / r=0.97 UK
This is your strongest and most defensible number. The parallel rise is exceptionally well-documented.
* USA: CDC National Diabetes Statistics Report: diagnosed diabetes rose from ~2.4% in 1980 to ~11.3% by 2020 — a near-linear rise perfectly tracking the rise in metabolic syndrome/IR prevalence over the same period.
* UK: NHS Digital: diagnosed T2DM rose from ~1.4 million (1996) to over 4.3 million by 2022. Diabetes UK reports prevalence more than tripled since the 1980s.
* IR parallel: NHANES data shows IR (by metabolic syndrome criteria) affected ~22% of US adults in 2003, rising to ~40% of adults aged 18–44 by 2021 (StatPearls/NCBI NBK507839).
* Verdict: r≈0.97–0.98 is fully plausible and very defensible. The Whitehall II data alone (HOMA-IR rising 15 years before T2DM diagnosis) gives you a mechanistic foundation that no other condition has.
2. Hypertension — r=0.97 USA / r=0.95 UK
* USA: NHANES data shows hypertension prevalence rose from ~24% in 1988–94 to ~47% by 2017–18 (Muntner et al., JAMA 2020). That’s a near-doubling in 30 years.
* UK: BHF Heart Statistics: hypertension affects over 14 million adults in England. Prevalence has risen consistently alongside obesity and metabolic syndrome markers.
* IR parallel: Ferrannini et al. (NEJM 1987) established the mechanistic link. The Uppsala study confirmed IR predicts hypertension incidence over 10 years.
* Verdict: A very high r is plausible. However, hypertension diagnosis rates are also partly driven by changing diagnostic thresholds (the 2017 ACC/AHA guideline change from 140/90 to 130/80 instantly added millions of Americans to the statistics). This is worth noting as a caveat.
3. Multiple Sclerosis — r=0.96 USA / r=0.97 UK
* USA: National MS Society: MS prevalence approximately doubled from ~250,000 in the 1970s to over 1 million by 2022 (Wallin et al., Neurology 2019 — the first rigorous national estimate).
* UK: MS Society UK: prevalence rose from ~85,000 estimated in the 1990s to ~130,000+ by 2020.
* IR parallel: MS has one of the stronger emerging IR/neuro-inflammation links in your dataset. Gut dysbiosis is now confirmed as a co-driver in MS (multiple studies 2017–2023).
* Verdict: The upward trend in MS is real and well-documented. However, some of the apparent prevalence increase reflects better MRI detection and longer survival rather than pure incidence increase. The r value is plausible but this caveat should be acknowledged. The mechanistic pathway (IR → neuro-inflammation → demyelination) is emerging rather than established.
4. Stroke — r=0.95 USA / r=0.93 UK
* USA: AHA/ASA stroke statistics: stroke remains a leading cause of death but the relationship is complex — stroke mortality has actually declined due to better treatment, while incidence in younger adults (under 65) has risen, linked to metabolic syndrome.
* UK: Stroke Association: similar pattern — mortality falling, but incidence in working-age adults rising.
* IR parallel: The 2022 Frontiers in Endocrinology systematic review confirmed IR as an independent predictor of stroke risk. The connection runs through hypertension, dyslipidaemia and atherosclerosis — all IR-downstream.
* Caution: Because stroke mortality has fallen (better acute treatment) while incidence has risen, the trend data you use matters enormously. If your IR index is being compared against stroke incidence in younger adults, r≈0.95 is very plausible. If compared against total stroke mortality, the correlation would be weaker or even negative. This is the r number most in need of explicit dataset citation.
5. ADHD — r=0.94 USA / r=0.91 UK
* USA: CDC NHIS data: parent-reported ADHD rose from 6.1% in 1997–98 to 10.2% in 2015–16 (Xu et al., JAMA Network Open 2018). By 2022, 11.4% of US children aged 3–17 had ever been diagnosed (CDC/Danielson et al. 2024).
* UK: NHS Digital ADHD prescriptions data shows a near-continuous rise. NHS England ADHD referrals increased by over 400% between 2019 and 2024.
* IR parallel: Mechanistic link via neuro-inflammation and dopaminergic disruption is published. Scandinavian studies show temporal correlation with childhood metabolic dysfunction.
* Caution: ADHD diagnosis rates are significantly influenced by diagnostic criteria changes (DSM-III to DSM-5), awareness campaigns, and prescribing culture shifts — particularly in the UK where diagnosis has historically been lower. A sceptic could argue much of the trend is diagnostic expansion rather than true incidence increase. Your r value is plausible but the confound is real and should be mentioned.
6. Asthma — r=0.89 USA / r=0.85 UK
* USA: CDC National Health Interview Survey: asthma prevalence rose from ~3% in the early 1970s to a peak of ~8.4% by 2010, then roughly plateaued. That plateau after 2010 is worth noting.
* UK: Asthma UK / NICE data: UK has some of the highest asthma rates in the world (~5.4 million affected). Prevalence rose steeply through the 1980s–90s, then flattened.
* IR parallel: The IR → leaky gut → systemic inflammation → airway hyperreactivity pathway is well-published. Beuther & Sutherland (AJRCCM 2007) confirmed obesity/IR and asthma are mechanistically linked.
* Caution: Asthma prevalence has plateaued or slightly declined in some datasets since ~2010, while IR has continued to rise. This divergence after 2010 would slightly reduce your r value if the full dataset to 2023 is used. r≈0.85–0.89 is plausible for a dataset ending around 2015; it becomes harder to defend to 2023.
7. IBS — r=0.93 USA / r=0.95 UK
* USA: IBS prevalence estimates range from 10–15% of the US population. Longitudinal national data is harder to find than for some other conditions, as IBS has historically been under-reported and variably diagnosed.
* UK: NHS/NICE: IBS affects 10–20% of UK adults. Diagnoses have risen consistently with increasing awareness.
* IR parallel: Reding et al. (Neuro-gastroenterology & Motility, 2011) confirmed significantly elevated IR in IBS patients vs. controls. The gut dysbiosis → IR → IBS loop is among the better-evidenced mechanistic connections in your dataset.
* Caution: Long-run trend data for IBS specifically (indexed back to 1975) is genuinely sparse. IBS was not consistently coded or reported in the 1970s–80s. This means the IBS trend line in your 50-year index likely relies more on extrapolation or proxy measures than the other conditions. This is your most data-sparse r value.
8. Arthritis — r=0.87 USA / r=0.83 UK
* USA: CDC arthritis data: doctor-diagnosed arthritis affected ~21% of US adults by 2015, projected to rise to 26% by 2040. CDC has tracked this since 2002; earlier data relies on NHANES estimates.
* UK: Arthritis Research UK / Versus Arthritis: over 10 million people affected in the UK; prevalence has risen with ageing population and obesity.
* IR parallel: The IR → adipokine dysregulation → synovial inflammation pathway is well-established for both OA and RA. Multiple meta-analyses confirm metabolic syndrome as a predictor of OA incidence.
* Caution: Arthritis prevalence is heavily confounded by population ageing — an older population will have more arthritis regardless of IR. Your index controls for this somewhat by using indexed growth rather than absolute numbers, but a sceptic will raise this. r≈0.83–0.87 is plausible but ageing is a substantial co-variable.
9. OCD — r=0.88 USA / r=0.86 UK
* USA: OCD prevalence estimates are ~1–3% of the population. Long-run trend data is genuinely limited — there is no equivalent of CDC’s diabetes or ADHD surveillance for OCD.
* UK: OCD-UK and NHS estimates suggest 750,000+ people affected. Diagnosis rates have risen with mental health awareness.
* IR parallel: The mechanistic link (IR → neuro-inflammation → glutamatergic/serotonergic dysregulation) is the most emerging in your dataset — it is scientifically credible but the fewest primary studies exist.
* Caution: OCD trend data going back to 1975 is the thinnest in your dataset. Much of the apparent prevalence rise reflects reduced stigma, better diagnosis, and awareness rather than confirmed incidence increase. Your r value for OCD is the one a peer reviewer would challenge most strongly.