Cortisol and ageing: how your stress hormone changes as you get older

As you get older, the shape of your cortisol day changes more than its overall level. The early-morning rise comes earlier, the night-time low is higher and the gap between the two narrows. Long-term cortisol, measured in hair, has been higher at older ages in several large studies, although not in all of them. In older adults, higher hair cortisol has been linked with diabetes, cardiovascular disease and carrying more weight. Those links are real findings, but most come from measuring people once, so they do not show that cortisol causes disease or speeds up ageing, and they cannot predict any one person's risk.

How the daily cortisol rhythm changes with age

In healthy adults, cortisol starts rising from about 4 in the morning, peaks within three hours of waking and falls through the day to a low point around midnight, with smaller pulses every one to two hours along the way.¹ With age, the difference between the daily high and low narrows, the early-morning rise comes earlier, the pulses get smaller and the night-time low rises.¹ The result is a flatter curve. Our guide to the cortisol daily rhythm explains the normal pattern in more detail.

A flatter, shifted curve makes one-off readings harder to interpret, because a single blood or saliva value taken at a random time is already hard to read.¹ Studies of both younger and older adults have found that saliva needs to be collected on at least three separate days for a reliable average, and on as many as ten days to describe how steeply cortisol falls through the day.² A hair sample averages the whole curve over roughly three months, so time-of-day changes matter much less.

Is long-term cortisol higher in older people?

Usually, but not always. Several studies that measured cortisol in hair found higher levels at older ages:

• In 654 German adults aged 47 to 82 in the EPIC-Potsdam study, hair cortisol rose with age. After allowing for many other factors, age and smoking were the only two that remained linked to it.³
• In 360 people aged 1 to 91, hair cortisol was raised in young children and in older adults.⁴
• In 760 Dutch adults, hair cortisol and cortisone were higher at older ages, and age remained a significant factor after adjustment.⁵

Other studies disagree. A South London community study found a small fall in hair cortisol with age (r = -0.17),⁶ and a 2026 study that set a reference range in 256 healthy Italian adults found no link with age at all.⁷ Differences in laboratory methods, and in how healthy the people studied were, may explain some of this. The fair summary is that hair cortisol tends to be higher at older ages, but age alone tells you little about any one person's level.

What large studies of older adults show

Hair sampling has made it practical to measure long-term cortisol in thousands of older people, and the Whitehall II study of 3,507 people aged 59 to 83 showed it can be done at that scale.⁸ Three cohort studies stand out:

• Whitehall II (UK). Diabetes, use of systemic steroid medicines and use of cardiovascular medicines were each linked to higher hair cortisol. People with depressive symptoms had 20.0 per cent higher levels.⁸
• English Longitudinal Study of Ageing. In 2,527 adults aged 54 and over, hair cortisol was higher in people with obesity and a larger waist, and in those whose obesity persisted over four years. The correlations with weight and body mass index were small, around r = 0.10.⁹
• Rotterdam. In 283 community-dwelling adults aged 65 to 85, high hair cortisol was linked with a history of cardiovascular disease (odds ratio 2.7) and type 2 diabetes (odds ratio 3.2), but not with other chronic diseases.¹⁰

For more on these links, see cortisol and heart health and cortisol and weight.

Association is not cause

It is tempting to read those findings as "high cortisol causes disease in later life". The evidence does not support that yet, for three reasons.

First, most of these studies measured hair cortisol and health at the same time, so they cannot show which came first. Illness and its treatment can raise cortisol. Several of the Whitehall II links were with medicines,⁸ and in critically ill patients cortisol production was 83 per cent higher than in controls.¹¹

Second, the effects are small for any one person. Across 26,527 people, the pooled correlation between hair cortisol and body mass index was r = 0.10.¹² A meta-analysis of eight studies found higher hair cortisol in people with cardiovascular disease, but results for the metabolic syndrome were inconsistent.¹³

Third, the strongest forward-looking evidence points to a related hormone. In the Lifelines cohort, followed for five to seven years, it was hair cortisone, the inactive form of cortisol, that predicted new cardiovascular disease, particularly in younger people.¹⁴ Hair cortisol is a useful measure of long-term exposure in research on ageing. It is not a test of biological age, and a single result cannot tell you your own risk of disease.

Taking a hair sample in later life

Hair testing works well at older ages, with a few points to bear in mind:

• Grey hair is fine. A study comparing pigmented and grey hairs from the same people found no difference between them.¹⁵
• Growth rates vary. Hair grows at different rates depending on age, sex and the individual,¹⁶ anywhere from 0.6 to 1.4 cm a month,¹⁷ so the months a sample covers are approximate.
• Thinning hair. Two or three small locks from neighbouring spots at the back of the head can be pooled. See cortisol and hair loss.
• Medicines. In the Lifelines cohort, people using only inhaled, nasal or skin steroids had lower hair cortisone,¹⁸ while systemic steroids were linked to higher hair cortisol in Whitehall II.⁸ Tell the laboratory about every steroid medicine you use.

Diabetes is linked to higher hair cortisol in several cohorts,⁵⁸ so a result makes most sense read alongside your health as a whole and compared with your own earlier results.

Can you change your cortisol as you get older?

A small number of trials have measured hair cortisol before and after a change in habits:

• Exercise. In a year-long trial of 130 adults aged 26 to 58, 150 minutes a week of moderate to vigorous aerobic exercise lowered hair cortisol compared with a group given health information.¹⁹ Intensive endurance training, by contrast, is linked to higher hair cortisol.²⁰
• Meditation. In a trial of meditation-based mental training, hair cortisol fell over the first three to six months, with no further fall by nine months.²¹
• Sleep. After a night of partial or total sleep loss, evening cortisol the next day was 37 to 45 per cent higher in one study,²² which is one reason sleep features in most advice on cortisol.

A review of 14 intervention studies found the effects on hair cortisol were mixed.²³ These trials measured cortisol and other markers, not whether people lived longer or avoided disease. For the full evidence, see how to lower cortisol.

When to see a doctor

Some cortisol problems are caused by medicines rather than by the body itself. The most common cause of Cushing's syndrome, too much cortisol, is taking high-dose steroid medicines for a long time.²⁴ At least 1 per cent of the population takes long-term steroid treatment and so is at risk of the opposite problem, adrenal insufficiency caused by the medicine.²⁵ If you take steroids, do not stop them suddenly without medical advice, and see a doctor about symptoms such as extreme tiredness, dizziness on standing, unexplained weight change or easy bruising. A hair test does not diagnose or rule out either condition.