Headache — and why it is almost never your blood pressure

The blood pressure belief

Almost every week someone arrives having had their blood pressure checked at a shop because of a headache, and having been told the two are connected. It is worth dealing with this first, because it is both the most widely held belief about headache here and the one most clearly contradicted by evidence.

A prospective study of 22,685 adults in Norway found that a systolic pressure of 150 mmHg or above was associated with a 30% lower risk of non-migrainous headache compared with below 140 (RR 0.7, 95% CI 0.6–0.8), that the risk fell as diastolic pressure rose, and that migraine showed no clear association with blood pressure at all.^[1] A population study in Nepal — the nearest comparable South Asian setting, 2,100 adults — found the same direction: an odds ratio of 0.6 (0.4–0.8) on bivariate analysis, and no significant association on multivariate analysis. The authors' conclusion was blunt: headache disorders and hypertension are unrelated entities.^[2]

What follows from that is not "ignore your blood pressure". High blood pressure needs finding and treating because of what it does to the heart, brain and kidneys over decades — see the blood pressure guide. It is simply that it is not the explanation for your headache, and treating the headache by adjusting antihypertensives is treating the wrong thing. Hypertensive emergency, pre-eclampsia and phaeochromocytoma are separate matters with their own presentations, and those are urgent.

What headache usually is

Two Indian population studies, both part of the Global Campaign against Headache, give consistent figures. In Karnataka, among 2,329 adults aged 18–65: any headache in the past year 63.9%, migraine 25.2%, tension-type headache 35.1%, headache on 15 or more days a month 3.0%, and probable medication-overuse headache 1.2%.^[3] In Delhi and the National Capital Region: any headache 67.9%, migraine 26.3%, tension-type 34.1%, probable medication-overuse headache 3.0%.^[4]

No population-based headache prevalence study has been done in West Bengal or eastern India, so those figures are used here as Indian estimates rather than local ones. What they establish is the base rate: primary headache is extremely common, and the great majority of headaches are migraine or tension-type.

The burden figures are worth quoting too, because migraine is routinely dismissed as a minor complaint. Indian migraineurs average 28 headache days a year, and 38% have three or more days a month affected; 5.8% of productive time is lost. Yet only 30.3% have ever consulted a doctor about it, against 16.6% for tension-type headache.^[5] Most migraine in this district is untreated, not because it is mild but because it is not brought in.

The painkillers that cause headache

This is the diagnosis most worth knowing about, because it is common, entirely reversible, and invisible unless specifically asked about. Taking acute painkillers too often — more than about ten to fifteen days a month, depending on the drug — converts an episodic headache into a daily one. The patient then takes more painkillers, and the cycle tightens.

What makes the Indian picture distinctive is which drug is responsible. In a series of 6,000 headache-clinic patients in India, medication-overuse headache accounted for 3.08%, and among those 184 cases the culprit was ergotamine in 56.5%, combination analgesics containing caffeine or codeine in 38.0%, and triptans in only 5.4%.^[6] That is the reverse of Western series, where triptans and simple analgesics dominate — and it matters because ergotamine-caffeine combinations remain cheap and widely available over the counter here.

The treatment is withdrawal of the overused drug together with a preventive medicine, and it works. But it cannot begin until the pattern is recognised, which is why the consultation asks not just what you take but how many days a month you take it. Bring the strips.

When a headache is not primary

In a tertiary headache clinic in eastern India, 30.75% of 400 patients had secondary headache, with intracranial haemorrhage and cerebral venous sinus thrombosis the commonest causes.^[7] That is a referral-filtered figure and is an upper bound — the proportion in general practice is much lower, generally quoted as 2–18% in emergency series.^[8] The point of red flags is to find the small number that matter without scanning everyone.

Cerebral venous thrombosis

This deserves particular attention here. It is a clot in the veins draining the brain, it presents with headache and vomiting, and it is far more prominent in Indian practice than in Western textbooks. In a study of 812 patients across nine Asian countries, anaemia was present in 51%, and pregnancy or the puerperium accounted for a substantial share of female cases.^[9] In Asian countries, pregnancy and the weeks after delivery account for around 36% of all cases.^[10] In the Indian i-RegVeD multicentre registry, headache was a presenting symptom in 29.6% and vomiting in 39.5%.^[11]

Set that against West Bengal, where 71.4% of women aged 15–49 are anaemic.^[12] A new, persistent, worsening headache in a woman who is anaemic, pregnant or recently delivered is not a headache to observe.

The eyes

Two eye conditions masquerade as headache often enough to be routine considerations. Uncorrected refractive error is the mundane one and the commonest: in an Indian series of 103 patients presenting with headache as their primary complaint, 28.2% had a refractive error — most often long-sightedness — and 69% were relieved by spectacles.^[13] Anyone with headache who has not had their eyes tested should have them tested.

Glaucoma is the serious one. An estimated 11.2 million Indians aged 40 and over have glaucoma, including 2.54 million with primary angle-closure glaucoma, and 27.6 million have some form of primary angle-closure disease — most of it undetected.^[14] Headache with eye pain, blurring, haloes around lights or a red eye needs an ophthalmologist, not an analgesic.

Infection, and one regional consideration

Tuberculous meningitis presents as a subacute headache building over days to weeks with fever, and in a systematic review of Indian meningitis series it accounted for 28% of cases in one mixed series and up to 47% of CNS infections among critically ill patients.^[15] The range is wide because the settings differ, and no single national figure is defensible — but in a high-TB-burden district a headache with fever over weeks is TB meningitis until excluded.

Neurocysticercosis — brain cysts from pork tapeworm — is a recognised cause of headache and seizure in India. The nearest studied population to the North Bengal tea belt is a tea-garden community in Assam, where 42.2% of people with active epilepsy met criteria for neurocysticercosis, and headache was the commonest presenting feature at 18.9%.^[16] No West Bengal prevalence data exists, so this is offered as a consideration in the right clinical context rather than a local statistic.

What is done at the consultation

The history does most of the work: how it started, how long each episode lasts, where the pain is, what it feels like, what makes it worse, whether there is aura, nausea, light or sound sensitivity, and — critically — how many days a month you take something for it. Blood pressure is measured. Examination includes the eyes. A blood count is checked, because anaemia is both common here and relevant to venous thrombosis.

Imaging is not routine. It is arranged when a red flag is present, when the pattern has changed, or when the examination is abnormal. Where it is needed it is arranged locally and the report reviewed with you at follow-up, which is not charged within 10 days.